# Tyres on the wrong way for over two years



## GuyBoden (9 Jun 2017)

I've had my tyres on the wrong way, the rear for over two years, I bought this year's tyre model yesterday and it now has a new arrow pointing in the direction of travel on the side wall.

Changed the tyres, so both are now the correct orientation, but, no discernible difference on my ride.


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## Flick of the Elbow (9 Jun 2017)

I've never paid any notice of those arrows. As you say, no discernible difference, not for a road tyre anyway. I imagine it would make a difference on a tyre designed for mud.


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## Ian H (9 Jun 2017)

Oh God! You might have died!

I'm sure one pair of tyres I fitted had instructions to fit the front with the arrow one way and the rear with it the other.


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## Alan O (9 Jun 2017)

There's no such thing as "wrong way" - it's marketing cowpoo.


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## Ajax Bay (9 Jun 2017)

They only put the arrow on to avoid people bothering them to ask 'Does it matter which way they go on?' or 'why is there no direction of rotation arrow?'
At least the tyres had decent tread so they gripped well.


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## Vantage (9 Jun 2017)

Tread on a car tyre is there to displace water. Bicycle tyres are too narrow for any water to accumulate under the tyre so tread on a road tyre is completely useless.
There's a study on tyre direction that says it makes not a jot of difference to the bikes handling regarding which direction they are fitted in. No idea where I saw that study though. Sowwy.


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## Vegan1 (9 Jun 2017)

Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water. It's correct to have the tyre arrow pointing towards the direction of travel.


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## Bollo (10 Jun 2017)

Vegan1 said:


> Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water. It's correct to have the tyre arrow pointing towards the direction of travel.


Let the carnival begin!


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## Drago (10 Jun 2017)

Tyres on the wrong way? You maniac!


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## DEFENDER01 (10 Jun 2017)

GuyBoden said:


> I've had my tyres on the wrong way, the rear for over two years, I bought this year's tyre model yesterday and it now has a new arrow pointing in the direction of travel on the side wall.
> 
> Changed the tyres, so both are now the correct orientation, but, no discernible difference on my ride.


I have had my tyres on the wrong way for 3 years.
I do sometimes reverse my bike they are then on the right way but i guess it would fail an M O T.


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## Shut Up Legs (10 Jun 2017)

GuyBoden said:


> I've had my tyres on the wrong way, the rear for over two years, I bought this year's tyre model yesterday and it now has a new arrow pointing in the direction of travel on the side wall.
> 
> Changed the tyres, so both are now the correct orientation, but, no discernible difference on my ride.


You realise the Velominati read CC? You're screwed.


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## ianrauk (10 Jun 2017)

It matters not


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## winjim (10 Jun 2017)

It's just the arrows? That's a relief, for a minute there I thought you'd been riding with a rear tyre on the front and a front on the rear. That would be silly.


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water. It's correct to have the tyre arrow pointing towards the direction of travel.


I cry BS!


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## Dirk (10 Jun 2017)

Many years ago we had a talk at our motorcycle club by Alan Blake, the head technical honcho at the time, from Avon Tyres.
He explained that during the manufacturing process the tread is put on the tyre carcass with a small amount of overlay, where one end sits on top of the other.
If the tyre was put on in the wrong direction, it could result in the tread lifting under heavy braking or acceleration. He showed us an example of a rear tyre that had done exactly that.
I doubt whether a cyclist could accelerate hard enough to cause tread lift, but heavy braking downhill at speed could possibly generate the conditions necessary for it to occur.


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> I cry BS!



How come?


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## Pale Rider (10 Jun 2017)

A bicycle cannot aquaplane, thus the tread plays no part in water displacement.

Strictly, a slick tyre will give marginally more grip on a wet road than a treaded one because there's more tyre in contact with the road surface.

Strictly, strictly, a bicycle could aquaplane if it went fast enough.

I think Schwalbe estimate 200km/h, or something like that.

So not a worry, even for Froomey in a hurry.


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## Vegan1 (10 Jun 2017)

Pale Rider said:


> A bicycle cannot aquaplane, thus the tread plays no part in water displacement.
> 
> Strictly, a slick tyre will give marginally more grip on a wet road than a treaded one because there's more tyre in contact with the road surface.
> 
> ...



Nice contradiction. Is this yours and everyone else's limit on here when it comes to discussing technical issues like the above? Not exactly elucidating. 

''I cry BS''


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## Globalti (10 Jun 2017)

Much more important than the baloney about treads and aquaplaning is the massive potential faux-pas of having the logo _on the wrong side of the bike_ if the tyre only has one logo so the arrow is there to ensure that you don't commit this grave error of style. For example, cognoscenti who use the world's best tyre, the superb Veloflex Open Corsa, will know this and will have the word "Veloflex" visible on the right of the bike and lined up with the valve or 180 degrees opposite, as it should be.


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## Tanis8472 (10 Jun 2017)

Contradiction?


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## Vegan1 (10 Jun 2017)

Where did aquaplaning come from? I'm talking about a tread pattern that displaces water?


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## Tanis8472 (10 Jun 2017)

Globalti said:


> Much more important than the baloney about treads and aquaplaning is the massive potential faux-pas of having the logo _on the wrong side of the bike_ if the tyre only has one logo so the arrow is there to ensure that you don't commit this grave error of style. For example, cognoscenti who use the world's best tyre, the superb Veloflex Open Corsa, will know this and will have the word "Veloflex" visible on the right of the bike and lined up with the valve or *180 degrees opposite*, as it should be.



It balances the tyre


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## Tanis8472 (10 Jun 2017)

Vegan1 said:


> Where did aquaplaning come from? I'm talking about a tread pattern that displaces water?



Car tyres, read back a few posts.


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## Pale Rider (10 Jun 2017)

Vegan1 said:


> Where did aquaplaning come from? I'm talking about a tread pattern that displaces water?



As I said, the tread pattern plays no part in displacing water.

On a bicycle, a slick tyre displaces water in the same way as a treaded one.

Thus the tread is irrelevant to water displacement.


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## Vegan1 (10 Jun 2017)

Tanis8472 said:


> Car tyres, read back a few posts.



I initially responded regarding a tread pattern on a tyre displacing water. Others have bought in aquaplaning.


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## Vegan1 (10 Jun 2017)

Pale Rider said:


> As I said, the tread pattern plays no part in displacing water.
> 
> On a bicycle, a slick tyre displaces water in the same way as a treaded one.
> 
> Thus the tread is irrelevant to water displacement.



No, I don't think a slick tyre would displace water in the same way that a treaded tyre would.


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## MontyVeda (10 Jun 2017)

What we need is 'the science bit'.


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## CanucksTraveller (10 Jun 2017)

GuyBoden said:


> I've had my tyres on the wrong way, the rear for over two years


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## GrumpyGregry (10 Jun 2017)

My kojaks have no tread. They work fine in the wet.

How is this possible without tread? Discuss.


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## Pale Rider (10 Jun 2017)

Vegan1 said:


> No, I don't think a slick tyre would displace water in the same way that a treaded tyre would.



Schwalbe disagree.

I will leave it to others to decide which of you may know more about bicycle tyres.

https://www.schwalbe.com/gb/profil.html


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## Tanis8472 (10 Jun 2017)

My head displaces water better without hair


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## Shut Up Legs (10 Jun 2017)

Vegan1 said:


> No, I don't think a slick tyre would displace water in the same way that a treaded tyre would.


https://www.sheldonbrown.com/gloss_ho-z.html
Search for 'hydroplaning' in the page.


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## Tanis8472 (10 Jun 2017)

> What does the tyre tread do?
> 
> 
> On a normal, smooth road, the tread has only limited influence on the riding properties. The grip generated by the tyre on the road is almost exclusively the result of the rubber compound.
> ...


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> My kojaks have no tread. They work fine in the wet.
> 
> How is this possible without tread? Discuss.




Not going to discuss an anecdote which is biased.


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## mjr (10 Jun 2017)

Yeah, I like some tread for biting quicker through mud/mulch. It might mean they throw the water off differently, but it's not needed for gripping through water at bicycle speeds and pressures.


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## Dirk (10 Jun 2017)

Vegan1 said:


> I initially responded regarding a tread pattern on a tyre displacing water. Others have bought in aquaplaning.


Tread patterns are there to displace water and thereby increase the speed at which aquaplaning occurs on tyres that have a combination of factors ie. low enough contact pressure, large enough contact area with the road surface or high enough speed to induce it.
Bicycle tyres achieve none of the above criteria; tread is only there for aesthetics.


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## Vegan1 (10 Jun 2017)

I've only ever made the point of a treaded tyre displacing water, nothing about aquaplaning.


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## Vegan1 (10 Jun 2017)

Dirk said:


> Tread patterns are there to displace water and thereby increase the speed at which aquaplaning occurs on tyres that have a low enough contact pressure, large enough contact area with the road surface or high enough speed to induce it.
> Bicycle tyres have none of the above criteria; tread is only there for aesthetics.



No, I'd still say that a treaded tyre displaces water.


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> Not going to discuss an anecdote which is biased.


Do you, or anyone else, have any _evidence_ that tread is necessary on road bike tyres?


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## Profpointy (10 Jun 2017)

Vegan1 said:


> I initially responded regarding a tread pattern on a tyre displacing water. Others have bought in aquaplaning.



Yebbutt you want to displace water to prevent aquaplaning - which will happe if you can go fast enough,which you can't


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> Do you, or anyone else, have any _evidence_ that tread is necessary on road bike tyres?



The above is not the issue here.


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## Tanis8472 (10 Jun 2017)

Of course it does. You have not, however, quantified how much.


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> No, I'd still say that a treaded tyre displaces water.


An untreaded tyre displaces water. A tyre made of smooth steel would displace water.


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## Vegan1 (10 Jun 2017)

Profpointy said:


> Yebbutt you want to displace water to prevent aquaplaning - which will happe if you can go fast enough,which you can't



Where is all this stuff about aquaplaning coming from?


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> An untreaded tyre displaces water. A tyre made of smooth steel would displace water.



Where have I said anything different to the above?


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## Pale Rider (10 Jun 2017)

Vegan1 said:


> Where is all this stuff about aquaplaning coming from?



It comes from people who credit you with enough intelligence to realise the only reason you want the tyre to displace water is to prevent aquaplaning.

On a bicycle, a slick tyre displaces water in the same way as a treaded one.


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> Do you, or anyone else, have any _evidence_ that tread is necessary on road bike tyres?



I don't have any evidence, could not tell you about anyone else. My point is that a treaded tyre displaces water.


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## Tanis8472 (10 Jun 2017)

Tread on a car tyre is there to move water away from the contact patch, thus making aquaplaning less likely (not impossible).
You mentioned on your first or second post that tread is there, like on a car tyre, to displace water.



> Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water. It's correct to have the tyre arrow pointing towards the direction of travel.


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## Ian H (10 Jun 2017)

Vegan1 said:


> I've only ever made the point of a treaded tyre displacing water, nothing about aquaplaning.


Aquaplaning = failure to displace water.

If a tyre isn't aquaplaning, it has displaced the water. Aquaplaning happens when the water hasn't been displaced. 

The footprint of a road tyre is smaller than any part of a car tyre between the sipes. So even at car speeds it's unlikely to aquaplane.

Tread on a bike tyre becomes useful off-tarmac.


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## Vegan1 (10 Jun 2017)

Ian H said:


> Aquaplaning = failure to displace water.
> 
> If a tyre isn't aquaplaning, it has displaced the water. Aquaplaning happens when the water hasn't been displaced.
> 
> ...



Thank you for the above, good to hear that the treaded tyres I have are doing thier job.


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## Ian H (10 Jun 2017)

Vegan1 said:


> Thank you for the above, good to hear that the treaded tyres I have are doing thier job.



Yes, exactly the same as slick tyres on tarmac.


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## Shut Up Legs (10 Jun 2017)

This is better than a helmet thread.


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## Hugh Manatee (10 Jun 2017)

GrumpyGregry said:


> My kojaks have no tread. They work fine in the wet.
> 
> How is this possible without tread? Discuss.



Yeah, but you must have got them on in the correct direction.


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## Profpointy (10 Jun 2017)

Vegan1 said:


> Where is all this stuff about aquaplaning coming from?



You only care about displacing water to prevent aquaplaning.


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## Pale Rider (10 Jun 2017)

Dogtrousers said:


> Tyre tread saved my life.



In the rain.


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## ufkacbln (10 Jun 2017)

Good way of making them last longer.

The wear on tread is different with the different rotation....

By reversing the tyres you can get double the life out of them


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## Welsh wheels (10 Jun 2017)

Shut Up Legs said:


> This is better than a helmet thread.


Gotta love the internet


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## davidphilips (10 Jun 2017)

Dogtrousers said:


> Tyre tread saved my life.



Was it the tread or the lack of rubber between the tread? If it was the lack of rubber then what was it? because there was nothing there?


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## ufkacbln (10 Jun 2017)

[QUOTE 4837234, member: 45"]Then you need to consider the next step:

Why would you want to displace water? What would this prevent? (if necessary)[/QUOTE]


The point of tread is to spray mud up the back of your jacket in a pattern that makes you look like a really hardened of roader


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## Dirk (10 Jun 2017)

Vegan1 said:


> No, I'd still say that a treaded tyre displaces water.


It does and it will displace more water than a slick.
It does this to increase the speed at which aquaplaning occurs. 
There is no other reason for having tread on a tyre used on tarmac.
However, since it has been explained several times that bikes don't aquaplane, due to several factors, the use of tread is purely cosmetic.


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## Vegan1 (10 Jun 2017)

Profpointy said:


> You only care about displacing water to prevent aquaplaning.


And what about grip?


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## Vegan1 (10 Jun 2017)

Dirk said:


> *It does and it will displace more water than a slick.*
> It does this to increase the speed at which aquaplaning occurs.
> There is no other reason for having tread on a tyre used on tarmac.
> However, since it has been explained several times that bikes don't aquaplane, due to several factors, the use of tread is purely cosmetic.



Thank you for agreeing my first post that I made in this thread.


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> And what about grip?


You should get one. 

Tread is irrelevant on tarmac from the pov of grip.


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## GrumpyGregry (10 Jun 2017)

Dirk said:


> *It does and it will displace more water than a slick*.
> It does this to increase the speed at which aquaplaning occurs.
> There is no other reason for having tread on a tyre used on tarmac.
> However, since it has been explained several times that bikes don't aquaplane, due to several factors, the use of tread is purely cosmetic.


That's questionable...


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> My point is that a treaded tyre displaces water.


Nope. Let's be clear. That was NOT your original point. Your original point was


Vegan1 said:


> Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water.


Why is there tread on a car tyre? To prevent aquaplaning.
Is that the same reason you have tread on a bicycle tyre? No, because unless Louis Hamilton is giving you a tow you can't aquaplane a bike tyre.

QED.


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## Vegan1 (10 Jun 2017)

[QUOTE 4837294, member: 45"]On a wet road, what makes you lose grip?

OK, I'll answer it for you. It's the water getting between the tyre and the road. People view aquaplaning as a car "surfing" on top of a pool of water, but this is the same concept that you're talking about.

A bike tyre is narrow enough that it simply pushes (with help from the downward force of you and the bike) the water to the sides, at any speed that you'd like to ride. A car tyre has a much wider, flat contact area, so tread is set into the tyre to allow channels for water to be pushed through and minimising the possibility of it getting between the rubber and the road and the car losing grip.

Tread on mountain bike tyres isn't there to prevent aquaplaning either. It's there to manage riding on loose and muddy surfaces. Like a tractor, and I can't think of a situation where a tractor might be at risk of aquaplaning.[/QUOTE]

It does not push the water to the sides. LOL


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## youngoldbloke (10 Jun 2017)

Vegan1 said:


> And what about grip?


'On a normal, smooth road, even in wet conditions, a slick tyre actually provides better grip than a tyre with a tread, because the contact area is larger.'
Didn't you read the Schwalbe information?


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## nickyboy (10 Jun 2017)

I've got to say this is top quality trolling


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## ufkacbln (10 Jun 2017)

winjim said:


> It's just the arrows? That's a relief, for a minute there I thought you'd been riding with a rear tyre on the front and a front on the rear. That would be silly.



Unless you cycle backwards:


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## ufkacbln (10 Jun 2017)

Vegan1 said:


> How come?



The relevant BS is BS ISO 5775-1:2014 Bicycle tyres and rims. Tyre designations and dimensions


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## Vegan1 (10 Jun 2017)

[QUOTE 4837315, member: 45"]*Where do you think it goes then?*

This is how discussion works -someone puts a view forward and then someone else agrees or disagrees. If you're disagreeing, you need to counter that view.

And preferably all of it, not just choosing one aspect you disagree with to distract from the rest of the quote that you can't.

So, can you flesh it out a bit?....[/QUOTE]

It remains on the road?


I can't see a road tyre providing enough force to completely displace water thus leaving the road which the tyre has just gone over dry.


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## Dayvo (10 Jun 2017)

Vegan1 said:


> And what about grip?


 
Hey, V1, if you've got a bike, turn your tyres inside out to see what happens.


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## ufkacbln (10 Jun 2017)

IIRC there was an argument between the followers of the late Sheldon Brown and those of Chris Boardman

Boardman stated that in the Tour de France in wet conditions riders used wider tyres with tread, whereas Sheldon Brown argued that the tread limited the contact area and was therefore the wrong decision.

There was no categorical answer


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## Dirk (10 Jun 2017)

GrumpyGregry said:


> That's questionable...


No it's not.
A treaded tyre does displace more water, under full wet ie. not just damp conditions, than a slick.


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## Dirk (10 Jun 2017)

Vegan1 said:


> Thank you for agreeing my first post that I made in this thread.


That was never an issue, so there is no need to thank me.
The issue is whether treaded tyres are necessary on a bicycle, in order to displace water on a tarmac surface. This was what your first post suggested.



Vegan1 said:


> Tread on a tyre is there for the same reason that you get tread on a car tyre to displace water. It's correct to have the tyre arrow pointing towards the direction of travel.



They are not there for that reason on bicycle tyres, due to reasons explained more than once.
Treads are there for purely cosmetic/marketing reasons.


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## Vegan1 (10 Jun 2017)

[QUOTE 4837336, member: 45"]*But not under the tyre, because then there would be no grip.*



It does. Otherwise you'd have no grip.[/QUOTE]



You riding on wet roads, not on ice. farking hell.


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## Alan O (10 Jun 2017)

Folks, here's a piece about tyre tread I read a while ago, which seems quite interesting - just found it again now...

http://www.bretonbikes.com/homepage...he-importance-of-tread-pattern-on-cycle-tyres

Ah, and here's Jobst Brandt on the same subject...

http://sheldonbrown.com/brandt/slicks.html


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> You riding on wet roads, not on ice. farking hell.


If the water is not displaced adequately you'd aquaplane.


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## Vegan1 (10 Jun 2017)

Dayvo said:


> Hey, V1, if you've got a bike, turn your tyres inside out to see what happens.



I feel like I've just wasted 20 minutes of my life, the above is really difficult.

Even with a foldable bead which I've got turning a tyre inside out to mount on a wheel is nigh on impossible.


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> If the water is not displaced adequately you'd aquaplane.



So what's with the wet trails after you've rode through a puddle?

I don't recall ever a tyres contact patch being dry after riding on wet roads.


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## Dirk (10 Jun 2017)

[QUOTE 4837336, member: 45"]It does. Otherwise you'd have no grip.[/QUOTE]
Not necessarily completely dry. 
Moving enough water to leave the surface damp is what generally happens. This is the point where a treaded tyre hasn't got enough surfacewater to shift and so becomes redundant. Due to various reasons discussed up thread, this point where a treaded tyre would start to work better than a slick is never reached on a bicycle. There is, however, a consequent diminishing of grip due to a slick tyre on a damp surface, which is why you don't corner as quick in the wet.


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## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> So what's with the wet trails after you've rode through a puddle?
> 
> I don't recall ever a tyres contact patch being dry after riding on wet roads.


The water is adequately displaced.

Now how about you admit that this is BS?


Vegan1 said:


> *Tread on a tyre is there for the same reason that you get tread on a car tyre* to displace water. .


Because...

The tread on a bike tyre is not there for the same reasons as the tread on a car tyre.
The tread on a bike tyre is not there to displace water.


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## GrumpyGregry (10 Jun 2017)

Dirk said:


> Not necessarily completely dry.
> Moving enough water to leave the surface damp is what generally happens. This is the point where a treaded tyre hasn't got enough surfacewater to shift and so becomes redundant. Due to various reasons discussed up thread, this point where a treaded tyre would start to work better than a slick is never reached on a bicycle. There is, however, a consequent diminishing of grip due to a slick tyre on a damp surface, which is why you don't corner as quick in the wet.


Grip is diminished when cornering due to change in shape and size of contact area and differing forces acting from different directions from when the bike is going straight ahead, as well, surely?


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## Alan O (10 Jun 2017)

Dirk said:


> Not necessarily completely dry.
> Moving enough water to leave the surface damp is what generally happens. This is the point where a treaded tyre hasn't got enough surfacewater to shift and so becomes redundant. Due to various reasons discussed up thread, this point where a treaded tyre would start to work better than a sllick is never reached on a bicycle. There is, however, a consequent diminishing of grip due to a slick tyre on a damp surface, which is why you don't corner as quick in the wet.


Yes indeed, there's always a microscopic thin layer of water left, and it's the irregularities in the road surface at that scale that penetrate it and 'key' with the deforming rubber of the tyre. And, of course, the microscopic layer of water is there under a treaded tyre just as much as a slick - but there's less rubber to key with the road surface.


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## GrumpyGregry (10 Jun 2017)

Dogtrousers said:


> No one's saying bike tyres don't get wet. They are saying that *They don't aquaplane*


What has aquaplaning got to do with anything?











Apart from being the reason why car tyres have tread.


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## Vegan1 (10 Jun 2017)

GrumpyGregry said:


> The water is adequately displaced.
> 
> Now how about you admit that this is BS?
> 
> ...



But in order for there to be a trail after riding through a puddle then there has to be water on the contact point of the tyre?

According to some this would mean no grip?

So how can a tyre leave a trail of water on the road but still have grip if there is water between the tyre and the road which would be the trail of water left on the road?


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## Alan O (10 Jun 2017)

Vegan1 said:


> I don't recall ever a tyres contact patch being dry after riding on wet roads.


Aw, come on, this really has to be a wind-up now


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## Dirk (10 Jun 2017)

GrumpyGregry said:


> Grip is diminished when cornering due to change in shape and size of contact area and differing forces acting from different directions from when the bike is going straight ahead, as well, surely?


Of course, but nobody is arguing those points.


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## Vegan1 (10 Jun 2017)

Dirk said:


> Not necessarily completely dry.
> Moving enough water to leave the surface damp is what generally happens. This is the point where a treaded tyre hasn't got enough surfacewater to shift and so becomes redundant. Due to various reasons discussed up thread, this point where a treaded tyre would start to work better than a slick is never reached on a bicycle. There is, however, a consequent diminishing of grip due to a slick tyre on a damp surface, which is why you don't corner as quick in the wet.



Good to see at least someone other than me has a good understanding of tyres in wet conditions. Unlike the other two.


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## Alan O (10 Jun 2017)

Vegan1 said:


> But in order for there to be a trail after riding through a puddle then there has to be water on the contact point of the tyre?
> 
> According to some this would mean no grip?
> 
> So how can a tyre leave a trail of water on the road but still have grip if there is water between the tyre and the road which would be the trail of water left on the road?


Because it's only necessary to displace sufficient water for the tyre rubber to key with the road surface.


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## Milkfloat (10 Jun 2017)

Shut Up Legs said:


> This is better than a helmet thread.


This is a helmet thread, well one of the posters is.


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## Globalti (10 Jun 2017)

I'm in South Africa where the winter sun is shining but I can tell it's raining in the UK as seven pages of argument have appeared on this thread since I posted earlier this morning. People ought to fit mudguards and get out more.


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## Dirk (10 Jun 2017)

Vegan1 said:


> Good to see at least someone other than me has a good understanding of tyres in wet conditions. Unlike the other two.


Give over!
This thread is obviously a wind up.
@Vegan1 - read this: http://www.bretonbikes.com/homepage...he-importance-of-tread-pattern-on-cycle-tyres

I can't be arsed with any more of your inane comments.
I'm out of here (for the time being anyway).


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## Vegan1 (10 Jun 2017)

[QUOTE 4837429, member: 45"]<prepares to be shot down>
Grip is actually increased when cornering, as you're introducing another force pushing onto the road, but the *"slide off"* point (don't know the technical term) is more dramatic and consequences of losing grip greater.[/QUOTE]

Co-efficient of friction.


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## Alan O (10 Jun 2017)

Dogtrousers said:


> Mudguards? You've just added a new dimension to the thread. Stand by for another 7 pages.


Mudguards saved my life once.


----------



## MontyVeda (10 Jun 2017)

A treaded tyre (especially concentric tread patterns) helps to enhance the gyroscopic affect that keeps a bicycle in motion upright much better than slick tyres...


----------



## GrumpyGregry (10 Jun 2017)

Vegan1 said:


> So how can a tyre leave a trail of water on the road but still have grip if there is water between the tyre and the road which would be the trail of water left on the road?



Irrelevant. 



Vegan1 said:


> *Tread on a tyre is there for the same reason that you get tread on a car tyre* to displace water. .



The tread on a bike tyre is not there for the same reasons as the tread on a car tyre.
The tread on a bike tyre is not there to displace water.

And that really is all there is to say on the matter.


----------



## Profpointy (10 Jun 2017)

Vegan1 said:


> Co-efficient of friction.



Limit of adhesion might be the term you're after. Co-efficient of friction is the ratio of downforce to available grip which isn't quite the same thing


----------



## Racing roadkill (10 Jun 2017)

The tyre's are directional for either the tread pattern to disperse water away from the tyre's centre, then away from the shoulders most efficiently, or because that's the direction in which the tread / rubber was laid on the carcass. You probably won't notice too much difference in performance unless you are braking very hard, riding with standing water, or cornering at high speed. Doing any of those things with the tyre on the wrong way round, will mean the tyre is not doing it's job as efficiently as it could, it could lead to a de lamination ( not good at speed, or cornering / braking hard) and the tyre will wear out more quickly ( whether you notice or not is a different story).


----------



## davidphilips (10 Jun 2017)

Alan O said:


> Mudguards saved my life once.



Raceblades killed my head set once, Think they would do it again but i fooled the craftie so and sos (that seems like a signal for help) by extending the front with some tape so the spray is not forced into the head set.

Now heres a good question how much slower do touring tyres make a road bike than slicks? 
Any one notice what a big difference tyres can make theres a group i go out with and to me they seem quite slow yet when i fitted touring tyres the group suddenly seemed quite fast?
refitted slicks and my bike was faster again?


----------



## postman (10 Jun 2017)

Look here are the instructions.The tyres were ok,it was the frame you had the wrong way round.


----------



## Smokin Joe (10 Jun 2017)

Racing roadkill said:


> The tyre's are directional for either the tread pattern to disperse water away from the tyre's centre, then away from the shoulders most efficiently,



Unless you can alter the molecular structure of water the pretty pattern that passes for a tread on a cycle tyre will shift bugger all.


----------



## Yellow Saddle (10 Jun 2017)

[QUOTE 4837429, member: 45"]<prepares to be shot down>
Grip is actually increased when cornering, as you're introducing another force pushing onto the road, but the "slide off" point (don't know the technical term) is more dramatic and consequences of losing grip greater.[/QUOTE]

No, it doesn't work like that. 
When cornering you have two forces acting on the tyre as you surmised. However, the one force is the Normal Force, which is your weight x the sine of the angle of lean. Doesn't matter what it is, but it is always less than the Normal Force at 90 degrees.
The centripetal force acts purely horizontally (no matter that the bike is leaning) and only has a negative effect on friction. It acts against available friction but doesn't add to it. Otherwise we'll be able to corner iniinitely fast.

The coefficient of friction is simply the "Strength" of the particular brand of friction you move or attempt to move two friction pairs (in this case rubber and asphalt) against each other.


----------



## Yellow Saddle (10 Jun 2017)

Racing roadkill said:


> The tyre's are directional for either the tread pattern to disperse water away from the tyre's centre, then away from the shoulders most efficiently, or because that's the direction in which the tread / rubber was laid on the carcass. You probably won't notice too much difference in performance unless you are braking very hard, riding with standing water, or cornering at high speed. Doing any of those things with the tyre on the wrong way round, will mean the tyre is not doing it's job as efficiently as it could, it could lead to a de lamination ( not good at speed, or cornering / braking hard) and the tyre will wear out more quickly ( whether you notice or not is a different story).



You are smoking your airless tyres again. But there's no reasoning with you. I'm just replying as a cautionary to others who may think you have a Phd in tribology too. You don't.


----------



## Yellow Saddle (10 Jun 2017)

Vegan1 said:


> I've only ever made the point of a treaded tyre displacing water, nothing about aquaplaning.


A smooth tyre displaces water perfectly well and suffers from none of the maladies that beset treaded bicycle tyres.


----------



## Yellow Saddle (10 Jun 2017)

Vegan1 said:


> It does not push the water to the sides. LOL



Where do you propose the water goes?


----------



## Randomnerd (10 Jun 2017)

I've had my helmet on back to front all day today, and had to cycle home in reverse to avoid aquaplaning...


----------



## Yellow Saddle (10 Jun 2017)

youngoldbloke said:


> 'On a normal, smooth road, even in wet conditions, a slick tyre actually provides better grip than a tyre with a tread, because the contact area is larger.'
> Didn't you read the Schwalbe information?



I'm afraid Schwalbe has it right, but for the wrong reason. In friction, the contact area is irrelevant. Fr= mu x Fn There is no provision for area in the formula.


----------



## Yellow Saddle (10 Jun 2017)

Vegan1 said:


> It remains on the road?
> 
> 
> I can't see a road tyre providing enough force to completely displace water thus leaving the road which the tyre has just gone over dry.


Then you have never ridden behind someone in the rain and noticed the trail of dry road behind the wheel that closes up as the water flows back.


----------



## Yellow Saddle (10 Jun 2017)

Alan O said:


> Yes indeed, there's always a microscopic thin layer of water left, and it's the irregularities in the road surface at that scale that penetrate it and *'key'* with the deforming rubber of the tyre. And, of course, the microscopic layer of water is there under a treaded tyre just as much as a slick - but there's less rubber to key with the road surface.


You got it wrong there. There is no mechanical interlocking of shapes creating a mechanical resistance of sorts. 

The rest is sound. The microscopic layer you refer to is the boundary layer and it increases grip over that of a bulk water layer. That's why you lick your fingers to open a plastic bag and not run it under the tap. However sticky, the boundary layer is still less grippy than the road irregularities it isolates from the rubber. These irregularities adhere to the tyre through Van der Waals forces, a chemical phenomena, not physical as "key" suggests.


----------



## Yellow Saddle (10 Jun 2017)

Cunobelin said:


> IIRC there was an argument between the followers of the late Sheldon Brown and those of Chris Boardman
> 
> Boardman stated that in the Tour de France in wet conditions riders used wider tyres with tread, whereas Sheldon Brown argued that the tread limited the contact area and was therefore the wrong decision.
> 
> There was no categorical answer


Boardman was wrong. He's no scientist.


----------



## davidphilips (10 Jun 2017)

woodenspoons said:


> I've had my helmet on back to front all day today, and had to cycle home in reverse to avoid aquaplaning...



Thought i seen you at the roundabout looked fun i waved but dont think you seen me because i waved in the direction you had been cycling from.


----------



## ColinJ (10 Jun 2017)

Cunobelin said:


> Boardman stated that in the Tour de France in wet conditions riders used wider tyres with tread ...


----------



## Alan O (10 Jun 2017)

Yellow Saddle said:


> You got it wrong there. There is no mechanical interlocking of shapes creating a mechanical resistance of sorts.
> 
> The rest is sound. The microscopic layer you refer to is the boundary layer and it increases grip over that of a bulk water layer. That's why you lick your fingers to open a plastic bag and not run it under the tap. However sticky, the boundary layer is still less grippy than the road irregularities it isolates from the rubber. These irregularities adhere to the tyre through Van der Waals forces, a chemical phenomena, not physical as "key" suggests.


Ah, got you, thanks.


----------



## Racing roadkill (10 Jun 2017)

Smokin Joe said:


> Unless you can alter the molecular structure of water the pretty pattern that passes for a tread on a cycle tyre will shift bugger all.


Depends on the depth and design. An M+ will work well, a GP4000sII, not so much.


----------



## ufkacbln (10 Jun 2017)

ColinJ said:


>




Should have listened to Sheldon?
\


----------



## Randomnerd (10 Jun 2017)

davidphilips said:


> Thought i seen you at the roundabout looked fun i waved but dont think you seen me because i waved in the direction you had been cycling from.


Next time, davidphilips, wave at where I'm going and I'll see you. I wasn't trying to avoid you, or being rude; had to get home quick so I could have the spare time to read all the bull on here.


----------



## smutchin (10 Jun 2017)

Vegan1 said:


> I don't have any evidence



The cornerstone of any argument on the internet. And proof that you are trolling. 



Cunobelin said:


> By reversing the tyres you can get double the life out of them



Much like underpants. 

[QUOTE 4837315, member: 45"]So, can you flesh it out a bit?....[/QUOTE]

He doesn't do flesh, he's a vegan.


----------



## Ajax Bay (10 Jun 2017)

Ajax Bay said:


> At least the tyres had decent tread so they gripped well.


Please note that I whistled - and am gratified that an enthusiast responded - and away we went - 9 pages!


Vegan1 said:


> I initially responded regarding a tread pattern on a tyre displacing water.


Well actually you can see that I didn't say anything about displacing water.


Vegan1 said:


> I don't think a slick tyre would displace water in the same way that a treaded tyre would.


Rubber presses down: water is squeezed away.


Shut Up Legs said:


> This is better than a helmet thread.


Thank you for the implicit cheer.


Racing roadkill said:


> The tyre's are directional for either the tread pattern to disperse water away from the tyre's centre, then away from the shoulders most efficiently, or because that's the direction in which the tread / rubber was laid on the carcass. You probably won't notice too much difference in performance unless you are braking very hard, riding with standing water, or cornering at high speed. Doing any of those things with the tyre on the wrong way round, will mean the tyre is not doing it's job as efficiently as it could, it could lead to a de lamination ( not good at speed, or cornering / braking hard) and the tyre will wear out more quickly ( whether you notice or not is a different story).


I will just assume you are just trolling - please put a smiley in so we know this. What treaded tyres do you run on your road bike, or are they treadless?


----------



## Bollo (10 Jun 2017)

Ajax Bay said:


> ... What treaded tyres do you run on your road bike, or are they treadless?


Roadkill. Tyres. Nooooooooooo!!!!!!!!!!


----------



## ColinJ (10 Jun 2017)

smutchin said:


> He doesn't do flesh, he's a vegan.


A bit of a has-bean ...?


----------



## winjim (10 Jun 2017)

Ajax Bay said:


> Please note that I whistled - and am gratified that an enthusiast responded - and away we went - 9 pages!


Top troll, and nobody even called you out on it since they were too busy arguing with the other guy...


----------



## Racing roadkill (10 Jun 2017)

Ajax Bay said:


> I will just assume you are just trolling - please put a smiley in so we know this. What treaded tyres do you run on your road bike, or are they treadless?









I use these Road bike tyre's with tread on the road bikes at present.







M+ with tread, on the Hybrids at present.

So no trolling.


----------



## Ajax Bay (10 Jun 2017)

Racing roadkill said:


> I use these Road bike tyre's with tread on the road bikes at present.


Thought I'd see what had been said about these tyres. Surprised you did not include the text immediately below the review (that you got the image from).
"slick (but not bald) treads offer the most convincing grip, especially when it's raining dogs and you're blasting through the bends. However, manufacturers recognise that patterns are psychologically reassuring."
Bit surprised you are running this rugged bargain basement tyre on Cosmics.






BTwin Resist 9 Road Bike Tyre 700X25
*BTwin's Resist 9 Road Bike Tyre is a rugged bargain basement 700x25c complete with puncture-preventing belts, 60tpi casings and deep, water-channelling tread.*
At first glance, the tread pattern of the Resist 9 looks quite aggressive, especially by contemporary tastes, and similar to that found on Vittoria's Randonneur series. Given that bicycles don't aquaplane, slick (but not bald) treads offer the most convincing grip, especially when it's raining dogs and you're blasting through the bends. However, manufacturers recognise that patterns are psychologically reassuring.


----------



## keithmac (10 Jun 2017)

Interesting thread!, can you get front and rear specific tyres for bicycles?.

From a motorcycle point of view the front and rear tread patterns are a reverse of each other (and front and rear specific tyres).

I've not looked massively into this but I sumise the following, the front tyres maximum loading is when heavy braking and this requires the maximum grip available from the tyre (clockwise force).

The rear tyres maximum loading is on full acceleration (anti-clockwise force). 

Seems the tread has more function than just water dispersion on motorcycle tyres as the tread pattern would be the same direction front and rear otherwise. (Tread blocks allow the compound to to heat up quicker, allowing a harder wearing compound).

Slick motorcycle tyres are like plasticine, you can dig your nails in and pull chunks of the compound off the tyre when cold!.

I suppose on a bicycle the brakes could apply the most force front and rear and that's why they are not wheel specific but just directional?.


----------



## Racing roadkill (10 Jun 2017)

Ajax Bay said:


> Thought I'd see what had been said about these tyres. Surprised you did not include the text immediately below the review (that you got the image from).
> "slick (but not bald) treads offer the most convincing grip, especially when it's raining dogs and you're blasting through the bends. However, manufacturers recognise that patterns are psychologically reassuring."
> Bit surprised you are running this rugged bargain basement tyre on Cosmics.
> View attachment 356565
> ...


Try it, then come back and tell us what you think.

They may be "bargain basement" but they are pretty good in my experience thus far.


----------



## fossyant (10 Jun 2017)

It's all about tyre compound on a bike, and even on MTB's I believe ! 

On a road bike, the tyre compound makes the difference, not tread. Off road, the knobbles, make a difference on the type of riding, but the compound even makes a difference for the 'experts'.

As this thread is about tarmac, then it's the tyre compound that gets the grip in all situations. I have tyres I like and don't like in certain conditions as I've ridden them lots. Tread, not needed on tarmac. 

On road going bikes, you don't need different compounds or treads front/back - the weight isn't high and there isn't a 1000cc motor powering it. MTB's then the tread pattern is a personal preference.


----------



## Ajax Bay (10 Jun 2017)

keithmac said:


> can you get front and rear specific tyres for bicycles?.


I had a pair of these Giant P-SL2 which were sold as specific to front and rear, which came on a bike I bought. Seems the tread compound was meant to be the difference. I do not recommend these tyres. First one then the other developed a side bulge: the diagonal carcass threads had failed - to the extent that the bulge started rubbing on the fork. Having made it home and replaced it, foolishly I did not replace its twin on the rear: same mode of failure 1500km later when it started fouling the seatstay - saved by a local bike shop.
"This new folding-bead slick tyre from Giant grips and handles well in a variety of conditions, with some clever features that lifts it above run-of-the-mill general purpose rubber. The tread compound is different front and rear – softer and grippier up front, more hard-wearing in the rear."


----------



## lutonloony (10 Jun 2017)

So if I can cycle fast enough in the rain, I should fit car tyres. Would the panel recommend radial or cross-ply?


----------



## Dirk (10 Jun 2017)

keithmac said:


> Slick motorcycle tyres are like plasticine, you can dig your nails in and pull chunks of the compound off the tyre when cold!


Not all of them. It depends on the compound.
A qualifying tyre would be a lot softer than one used to do a full race distance.


----------



## Racing roadkill (10 Jun 2017)

fossyant said:


> It's all about tyre compound on a bike, and even on MTB's I believe !
> 
> 
> .



You believe wrong. The critical metric is 'mu'. mu is most influenced by compound, but the chemical reaction between the rubber and the tarmac, is also drastically effected by whether or not the compound is in direct contact with the tarmac. Anything that helps move water away from the contact patch helps dramatically. It's particularly noticeable with braking and acceleration in a straight line. If you cane it into a corner on a slick, under braking, and do the same on a treaded tyre, the outcomes are going to be different. How you deal with it is also going to vary, but the bottom line is, mu is increased if the contact patch is directly attatched to the tarmac.


----------



## Jenkins (10 Jun 2017)

keithmac said:


> Interesting thread!, can you get front and rear specific tyres for bicycles?.


Continental sell them as a pair


----------



## winjim (10 Jun 2017)

Yellow Saddle said:


> I'm afraid Schwalbe has it right, but for the wrong reason. In friction, the contact area is irrelevant. Fr= mu x Fn There is no provision for area in the formula.





Racing roadkill said:


> You believe wrong. The critical metric is 'mu'. mu is most influenced by compound, but the chemical reaction between the rubber and the tarmac, is also drastically effected by whether or not the compound is in direct contact with the tarmac. Anything that helps move water away from the contact patch helps dramatically. It's particularly noticeable with braking and acceleration in a straight line. If you cane it into a corner on a slick, under braking, and do the same on a treaded tyre, the outcomes are going to be different. How you deal with it is also going to vary, but the bottom line is, mu is increased if the contact patch is directly attatched to the tarmac.


OK, you both lose a mark for not properly defining your terms, but what I'm more interested in is the chemical reaction between rubber and tarmac. How does that work then?


----------



## Racing roadkill (10 Jun 2017)

Ajax Bay said:


> I had a pair of these Giant P-SL2 which were sold as specific to front and rear, which came on a bike I bought. Seems the tread compound was meant to be the difference. I do not recommend these tyres. First one then the other developed a side bulge: the diagonal carcass threads had failed - to the extent that the bulge started rubbing on the fork. Having made it home and replaced it, foolishly I did not replace its twin on the rear: same mode of failure 1500km later when it started fouling the seatstay - saved by a local bike shop.
> "This new folding-bead slick tyre from Giant grips and handles well in a variety of conditions, with some clever features that lifts it above run-of-the-mill general purpose rubber. The tread compound is different front and rear – softer and grippier up front, more hard-wearing in the rear."


The 'nd' figure ( stress corrosion coefficients) are different. The front tyre is designed to cope with more deformations ( due to steering trail, as well as the accelerations that the rear is subject to). The front tyre should have a higher 'nd' than the rear tyre. Again it's casting pearls before swine, for the most part, but if you know what you're doing, the difference, should be advantageous.


----------



## Racing roadkill (10 Jun 2017)

winjim said:


> OK, you both lose a mark for not properly defining your terms, but what I'm more interested in is the chemical reaction between rubber and tarmac. How does that work then?


That's the thing that makes the tyre work. It's a base principle, without it, the tyre can't work. I could go hunting for the relavant abstracts, but I can't be arsed.


----------



## S-Express (10 Jun 2017)

Ajax Bay said:


> Bit surprised you are running this rugged bargain basement tyre on Cosmics.



On the upside though, it might mean he's ditched the solid comedy tyres...


----------



## Bollo (10 Jun 2017)

winjim said:


> OK, you both lose a mark for not properly defining your terms, but what I'm more interested in is the chemical reaction between rubber and tarmac. How does that work then?





Racing roadkill said:


> That's the thing that makes the tyre work. It's a base principle, without it, the tyre can't work. I could go hunting for the relavant abstracts, but I can't be arsed.


That's stretching the definition of 'chemical reaction' more than just a little. There are plenty of definitions out there, but this one is reasonable ....

"a process that involves rearrangement of the molecular or ionic structure of a substance"

The tyre rubber does not become something else. The tarmac does not become something else. The grip is provided by the physical interface between tyre and tarmac (with maybe some water in the way if it's wet). For cycling at least, the heat generated by the action of friction on tyre and tarmac won't be enough to change the chemical composition of either. Even if bits of the tyre wear away, that's no more a chemical reaction than me hitting a banana with a hammer is a chemical reaction.


----------



## davidphilips (10 Jun 2017)

lutonloony said:


> So if I can cycle fast enough in the rain, I should fit car tyres. Would the panel recommend radial or cross-ply?



Yes radial or cross ply, if you cycle fast enough you will arrive before you started and hence not have to worry about tyres its something to do with flux capicators.


----------



## smutchin (10 Jun 2017)

Radial tyres on a bike feel really weird. I can't remember who it is that makes them (Maxxis?) but I don't want to ride them again.


----------



## Dirk (10 Jun 2017)

Racing roadkill said:


> That's the thing that makes the tyre work. It's a base principle, without it, the tyre can't work. I could go hunting for the relavant abstracts, but I can't be arsed.


As @Bollo says, there is no chemical reaction between the tyre and the road surface.
The tyre compound changes its grip characteristics due to it heating up through friction and distortion.


----------



## winjim (10 Jun 2017)

Racing roadkill said:


> That's the thing that makes the tyre work. It's a base principle, without it, the tyre can't work. I could go hunting for the relavant abstracts, but I can't be arsed.


No further questions.


----------



## S-Express (10 Jun 2017)

Don't forget, racing roadkill probably has a PhD in this stuff and has forgotten more about it than any of us will ever hope to know...


----------



## deptfordmarmoset (10 Jun 2017)

I've arranged my arrows so that they spend and equal amount of time pointing forwards (where I want to go), up (to make me lighter), down (to give me traction) and backwards (to remind me which way home is). Makes sense to me. No idea which way they're pointing at any given moment though.


----------



## Racing roadkill (10 Jun 2017)

Bollo said:


> That's stretching the definition of 'chemical reaction' more than just a little. There are plenty of definitions out there, but this one is reasonable ....
> 
> "a process that involves rearrangement of the molecular or ionic structure of a substance"
> 
> The tyre rubber does not become something else. The tarmac does not become something else. The grip is provided by the physical interface between tyre and tarmac (with maybe some water in the way if it's wet). For cycling at least, the heat generated by the action of friction on tyre and tarmac won't be enough to change the chemical composition of either. Even if bits of the tyre wear away, that's no more a chemical reaction than me hitting a banana with a hammer is a chemical reaction.


Do some reading on 'surface chemistry' come back in about 3 to 4 years, see if your opinion has changed. And see just how wrong what you just posted actually is.


----------



## Racing roadkill (10 Jun 2017)

Dirk said:


> As @Bollo says, there is no chemical reaction between the tyre and the road surface.
> The tyre compound changes its grip characteristics due to it heating up through friction and distortion.


You have no idea how wrong you are. Have a scout about on 'surface chemistry' and the interactions between rubber tyre compounds and tarmac. I'll see you in a few years, or not.


----------



## Racing roadkill (10 Jun 2017)

winjim said:


> No further questions.


Good, there's only so much casting of pearls before swine, and head into wall banging I'm going to do.


----------



## Dirk (10 Jun 2017)

Racing roadkill said:


> You have no idea how wrong you are. Have a scout about on 'surface chemistry' and the interactions between rubber tyre compounds and tarmac. I'll see you in a few years, or not.


I'm sorry, I really don't have the time or inclination.
As you are no doubt an expert in this field, maybe you could explain it for those of us who don't have this knowledge.


----------



## Yellow Saddle (10 Jun 2017)

winjim said:


> OK, you both lose a mark for not properly defining your terms, but what I'm more interested in is the chemical reaction between rubber and tarmac. How does that work then?


There is no chemical reaction. What causes friction is a phenomena in physical chemistry. It is a polar attraction between the molecules of the two substances and NOT a chemical REACTION. I think I have already explained - Van der Waal's force.


----------



## Racing roadkill (10 Jun 2017)

Dirk said:


> I'm sorry, I really don't have the time or inclination.
> As you are no doubt an expert in this field, maybe you could explain it for those of us who don't have this knowledge.


No, for that you'll have to get an education. That's not my problem.


----------



## Yellow Saddle (10 Jun 2017)

As usual, the local PfarkingHD gets it wrong:

surface chemistry
_noun_

the branch of chemistry concerned with the processes occurring at interfaces between phases, especially that between liquid and gas.
Anyone here change phase in tyre compound when riding?

Every village has an idiot.


----------



## Profpointy (10 Jun 2017)

Yellow Saddle said:


> As usual, the local PfarkingHD gets it wrong:
> 
> surface chemistry
> _noun_
> ...



Umm, you have solid (tyre, road) and liquid (water). Different phases no?


----------



## Yellow Saddle (10 Jun 2017)

Profpointy said:


> Umm, you have solid (tyre, road) and liquid (water). Different phases no?


NO.


----------



## deptfordmarmoset (10 Jun 2017)

Yellow Saddle said:


> NO.


Nitrous Oxide?


----------



## Profpointy (10 Jun 2017)

Yellow Saddle said:


> NO.



solid, liquid and gas are 3 different phases.


----------



## Yellow Saddle (10 Jun 2017)

Profpointy said:


> solid, liquid and gas are 3 different phases.



And?

.


----------



## S-Express (10 Jun 2017)

deptfordmarmoset said:


> Nitrous Oxide?



N2O


----------



## Profpointy (10 Jun 2017)

Yellow Saddle said:


> And?
> 
> .



Well you said it can't be surface chemistry as there aren't two phases,when manifesrly there are.

Quite apart from that point even my limited gentleman amateur level of science knows there are some fairly strange chemistry type effects going on in real world friction yet you dismiss this based on presumably half-remembered a-levels or whatever and justify it with jargon. I suspect racing roadkill is not making it up and does actually know a bit about this.


----------



## deptfordmarmoset (10 Jun 2017)

S-Express said:


> N2O


Dinitrous Monoxide then. I don't really care.


----------



## winjim (10 Jun 2017)

Yellow Saddle said:


> There is no chemical reaction. What causes friction is a phenomena in physical chemistry. It is a polar attraction between the molecules of the two substances and NOT a chemical REACTION. I think I have already explained - Van der Waal's force.


I know that, you know that...

ETA: The chemistry bit I mean. I don't think in fact it's all entirely explained by VdW forces.


----------



## Yellow Saddle (10 Jun 2017)

Profpointy said:


> Well you said it can't be surface chemistry as there aren't two phases,when manifesrly there are.
> 
> Quite apart from that point even my limited gentleman amateur level of science knows there are some fairly strange chemistry type effects going on in real world friction yet you dismiss this based on presumably half-remembered a-levels or whatever and justify it with jargon. I suspect racing roadkill is not making it up and does actually know a bit about this.



What do you mean by "Real world friction" and where did I say there aren't two phases?


----------



## S-Express (10 Jun 2017)

deptfordmarmoset said:


> Dinitrous Monoxide then. I don't really care.



Nitrogen Oxide is the one you're looking for...


----------



## jayonabike (10 Jun 2017)

12 pages.

12 f***ing pages. 

The OP only noticed his tyres were on the wrong way. 

F**k me. 

*Goes off to pour another whisky*


----------



## winjim (10 Jun 2017)

S-Express said:


> Nitrogen Oxide is the one you're looking for...


Nitric oxide


----------



## S-Express (10 Jun 2017)

winjim said:


> Nitric oxide



AKA nitrogen oxide.


----------



## winjim (10 Jun 2017)

S-Express said:


> AKA nitrogen oxide.


Not really. Nitrogen monoxide maybe.


----------



## S-Express (10 Jun 2017)

winjim said:


> Not really. Nitrogen monoxide maybe.



Maybe look it up.



> Nitrogen Oxide may refer to a binary compound of oxygen and nitrogen, or a mixture of such compounds:
> 
> 
> Nitric oxide, also known as nitrogen monoxide (NO), nitrogen(II) oxide


----------



## winjim (11 Jun 2017)

S-Express said:


> Maybe look it up.


Er yeah. So_ any_ compound containing _only_ nitrogen and oxygen. Not just NO. Each of those terms for NO contains reference to the +2 oxidation state of nitrogen in that compound. The term _nitrogen oxide_ is not that specific.


----------



## raleighnut (11 Jun 2017)

I like these,


----------



## Dirk (11 Jun 2017)

Racing roadkill said:


> No, for that you'll have to get an education. That's not my problem.


Prize cop out, just what I was expecting.


----------



## Bollo (11 Jun 2017)

Racing roadkill said:


> Do some reading on 'surface chemistry' come back in about 3 to 4 years, see if your opinion has changed. And see just how wrong what you just posted actually is.


Ok. Let's do a little thought experiment.Take two heavy blocks of - for simplicity sake - salt. NaCl - old salty. place one block on top of the other and then put them both in a vacuum. Now try and slide the top one over the bottom one.

According to you, there has to be "surface chemistry" going on for friction, right? But all we've got is sodium and chlorine. The only thing salt can do chemically in a vacuum is separate into sodium metal and chlorine gas. I ask you.....

In this experiment, do we see sodium and chlorine formed when we shove the salt block?
Or
Is there no friction.

Those are the only two options based on your argument.

Over to you.

As for my education, ironically I do have a physics PhD, although it's in nuclear physics. Ignoring the time I spent post-docing, that's 7 years very focused education.

I'm happy to acknowledge that this doesn't make me an expert, but it does give me some of the tools to analyse the problem.

I've presented two arguments to say your talking guff and all you've done is insult me and anyone else who's disagreed. It's not there first time we've been here, is it? Come up with some evidence instead of saying "I can't be arsed because I'm so special" or step out.


----------



## S-Express (11 Jun 2017)

winjim said:


> Er yeah. So_ any_ compound containing _only_ nitrogen and oxygen. Not just NO. Each of those terms for NO contains reference to the +2 oxidation state of nitrogen in that compound. The term _nitrogen oxide_ is not that specific.


Thanks for making my point.


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> I know that, you know that...
> 
> ETA: The chemistry bit I mean. I don't think in fact it's all entirely explained by VdW forces.



I disagree with what I think you are saying but before I present a counter argument, please explain what you mean by the* it* in "it's not entirely explained"


----------



## lutonloony (11 Jun 2017)

I bought a new tyre last week. It's got some tread on. It rained yesterday, I didn't fall off. So the tread saved the day. My other tyre is a slick, that seemed to do the job too. Just saying


----------



## Yellow Saddle (11 Jun 2017)

Bollo said:


> Ok. Let's do a little thought experiment.Take two heavy blocks of - for simplicity sake - salt. NaCl - old salty. place one block on top of the other and then put them both in a vacuum. Now try and slide the top one over the bottom one.
> 
> According to you, there has to be "surface chemistry" going on for friction, right? But all we've got is sodium and chlorine. The only thing salt can do chemically in a vacuum is separate into sodium metal and chlorine gas. I ask you.....
> 
> ...



I can see a third option and that depends where in the vessel you are detecting for the two elements.

Henceforth, can we please allow all arguments to stand on their own legs and speak for themselves and not be bolstered by framed certificates on the wall?


----------



## Yellow Saddle (11 Jun 2017)

lutonloony said:


> I bought a new tyre last week. It's got some tread on. It rained yesterday, I didn't fall off. So the tread saved the day. My other tyre is a slick, that seemed to do the job too. Just saying



Parallel universes, and I have a PhD in string theory.


----------



## keithmac (11 Jun 2017)

What about 2 cubes of steel, one on top of the other. I always though friction (caused by the weight of the top cube and the surface of the steel) was the only factor in making it hard to slide over the bottom cube.

Is there surface chemistry going on here as well?, I'm genuinely interested by the way!.


----------



## Dec66 (11 Jun 2017)

I'm preparing Old Reliable for our trip to France next weekend, part of which involved fitting the Vittoria Rubino Pro's I bought from @vickster a few weeks ago.

I spotted the rotation arrow, and thought I'd ensured that I'd fitted them correctly. When I looked this morning, however, I discovered they were the wrong way round...

So, an extra job today, one which I dislike immensely. I reckon the local foxes swapped them round overnight.


----------



## vickster (11 Jun 2017)

Dec66 said:


> I'm preparing Old Reliable for our trip to France next weekend, part of which involved fitting the Vittoria Rubino Pro's I bought from @vickster a few weeks ago.
> 
> I spotted the rotation arrow, and thought I'd ensured that I'd fitted them correctly. When I looked this morning, however, I discovered they were the wrong way round...
> 
> So, an extra job today, one which I dislike immensely. I reckon the local foxes swapped them round overnight.


I managed one the right way round when swapping Duranos onto my CX. All good practice! Luckily the rear one was correct


----------



## Dec66 (11 Jun 2017)

vickster said:


> I managed one the right way round when swapping Duranos onto my CX. All good practice! Luckily the rear one was correct


You don't even need the rotation arrows on the Rubinos to tell you the correct orientation, the tread pattern makes it self evident. And yet...

I think I just go a bit *duh* when spanners, or indeed tyre levers, find their way into my hands.


----------



## ufkacbln (11 Jun 2017)

The other possibility of course for the front wheel is that the tyre was fitted correctly, and the _*wheel*_ is the wrong way round


----------



## vickster (11 Jun 2017)

I just got confused as the the bike was upside down


----------



## vickster (11 Jun 2017)

Cunobelin said:


> The other possibility of course for the front wheel is that the tyre was fitted correctly, and the _*wheel*_ is the wrong way round


Yes that could have been a solution, but then the QRs would have been on opposite sides, an aesthetic no for me!


----------



## raleighnut (11 Jun 2017)

vickster said:


> Yes that could have been a solution, but then the QRs would have been on opposite sides, an aesthetic no for me!


Take the QR out and turn it round before re-inserting?


----------



## vickster (11 Jun 2017)

I needed tyre changing practice


----------



## Dirk (11 Jun 2017)

14 pages and not a sign of the OP since the first post........


----------



## MontyVeda (11 Jun 2017)

This has been a lot more fun than a random post in Mundane News though... well... at least until the phd willy waving bit.


----------



## Yellow Saddle (11 Jun 2017)

keithmac said:


> What about 2 cubes of steel, one on top of the other. I always though friction (caused by the weight of the top cube and the surface of the steel) was the only factor in making it hard to slide over the bottom cube.
> 
> Is there surface chemistry going on here as well?, I'm genuinely interested by the way!.


It depends on what you mean by "chemistry" and I don't want to get into a semantic war on this. It won't be helpful. 

The branch of science concerned with friction (there are of course overlaps) is physical chemistry and when it leans over to the engineering side, tribology. Very very simplistically, this differs from pure chemistry where molecules bond by sharing electrons. In physical chemistry we are concerned with the interaction of molecules at close quarters rather than chemical reactions and bonds. "Close quarters" being in the nanometer range. 
At this level a very weak force, Van der Waals comes to play. This weak force is caused by a temporary polarity within a molecule that attracts another temporary polarity in another molecule. 

I'll attempt with a (obviously silly) example. If you represent molecules with tennis balls and assume that inside the tennis ball there is a bunch of positive and negative charges floating around in a fluid, you can imagine that if you bring a "magnet" close to the tennis ball, the charged particles inside will polarise. In other words, more positive charges will move towards the magnet than negative charges and the charge balance within the ball changes. The charge becomes lopsided inside the ball but no charges escape the ball (as it does in chemical reactions). If you take the magnet away, the charges inside the ball normalise again. When you press two substances together so that close contact (5 or so nanometer distance between molecules) is made, then adjacent molecules from the two camps temporarily re-arrange themselves and attract each other.

That is friction. It is very easily destroyed by distance. All you have to do to release the two adhering/cohering objects is to increase the distance between them slightly. This is usually done in friction examples most people understand, by reducing the Normal Force (downforce, if you like) on the two objects. 

Although Van der Waal's is a very weak force, it accumulates nicely to amplify. To amplify it (get more molecules to attract each other) you just have to press them together so that at the micro structure more molecules meet and greet. 

Back to your steel blocks. Friction is the only force that resists the sliding of the two over each other. By generating enough Normal Force between the two, friction is powerful enough to weld the two blocks together (galling of bearings).


----------



## winjim (11 Jun 2017)

S-Express said:


> Thanks for making my point.


NO.


----------



## winjim (11 Jun 2017)

Yellow Saddle said:


> I disagree with what I think you are saying but before I present a counter argument, please explain what you mean by the* it* in "it's not entirely explained"


I mean I don't expect that VdW forces are the sole contributor to frictional forces in the case of a tyre gripping the road.


----------



## Smokin Joe (11 Jun 2017)

*Next week's hot topic:*

Tea, does the milk go in the cup first or last?

And does it matter which way you stir?


----------



## Alan O (11 Jun 2017)

Smokin Joe said:


> *Next week's hot topic:*
> 
> Tea, does the milk go in the cup first or last?
> 
> And does it matter which way you stir?


It depends on which end you eat your boiled egg from.


----------



## Dirk (11 Jun 2017)

Smokin Joe said:


> *Next week's hot topic:*
> 
> Tea, does the milk go in the cup first or last?
> 
> And does it matter which way you stir?


Milk?!


----------



## Racing roadkill (11 Jun 2017)

Now I've put the trolls back in the box, lets see if anyone who actually has a clue wants to contribute.


----------



## Racing roadkill (11 Jun 2017)

keithmac said:


> What about 2 cubes of steel, one on top of the other. I always though friction (caused by the weight of the top cube and the surface of the steel) was the only factor in making it hard to slide over the bottom cube.
> 
> Is there surface chemistry going on here as well?, I'm genuinely interested by the way!.


Possibly, but it would require something else to be there as well, bi metallics can react, and similar metals can react in the presence of a suitable antagonist, but your scenario is most likely to be purely mechanical in nature.


----------



## Racing roadkill (11 Jun 2017)

Alan O said:


> It depends on which end you eat your boiled egg from.


Or indeed, 'how do you peel your banana'


----------



## Racing roadkill (11 Jun 2017)

Dec66 said:


> You don't even need the rotation arrows on the Rubinos to tell you the correct orientation, the tread pattern makes it self evident. And yet...
> 
> I think I just go a bit *duh* when spanners, or indeed tyre levers, find their way into my hands.


If it's the front wheel, no great shakes, but putting the rear tyre on the wrong way is much more irritating. Many times have I been stood with the wheel in my hands, like a big steering wheel, and the tyre on loosely, doing the 'rotating the wheel, with a puzzled expression on the face' thing.


----------



## Racing roadkill (11 Jun 2017)

Cunobelin said:


> The other possibility of course for the front wheel is that the tyre was fitted correctly, and the _*wheel*_ is the wrong way round


There is no spoon.


----------



## Racing roadkill (11 Jun 2017)

winjim said:


> I mean I don't expect that VdW forces are the sole contributor to frictional forces in the case of a tyre gripping the road.


But they are most important in making sure that water is a liquid ( if it was completely pure water, it would be right on the transition from solid to liquid though ) at standard temperatures and pressures.


----------



## ufkacbln (11 Jun 2017)

Friend of mine had their quick release skewers the wrong way round!


----------



## S-Express (11 Jun 2017)

winjim said:


> NO.



N2O?


----------



## S-Express (11 Jun 2017)

Racing roadkill said:


> Now I've put the trolls back in the box, lets see if anyone who actually has a clue wants to contribute.



Ironic post of the day.


----------



## winjim (11 Jun 2017)

Racing roadkill said:


> But they are most important in making sure that water is a liquid ( if it was completely pure water, it would be right on the transition from solid to liquid though ) at standard temperatures and pressures.


Nah. Hydrogen bonding, innit.


----------



## davidphilips (11 Jun 2017)

Cunobelin said:


> Friend of mine had their quick release skewers the wrong way round!



Are you sure the skewers are on the wrong way it could be the bike fitted the wrong way onto the skewers?


----------



## ufkacbln (11 Jun 2017)

davidphilips said:


> Are you sure the skewers are on the wrong way it could be the bike fitted the wrong way onto the skewers?



True.....


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> I mean I don't expect that VdW forces are the sole contributor to frictional forces in the case of a tyre gripping the road.


What other mechanisms do you propose? And to be clear, "road" is dry asphalt/cement.


----------



## Yellow Saddle (11 Jun 2017)

Racing roadkill said:


> Possibly, but it would require something else to be there as well, bi metallics can react, and similar metals can react in the presence of a suitable antagonist, but your scenario is most likely to be purely mechanical in nature.



Read again: "Two cubes of steel." Where's the bi-metal in that?

Further, there is NO mechanical interlocking at play in the scenario proposed. Friction does not rely on mechanical interlocking.


----------



## Racing roadkill (11 Jun 2017)

Cunobelin said:


> Friend of mine had their quick release skewers the wrong way round!


Many a true word spoken in jest. I've had riders with the cams on the 'drop' side, they've come a cropper and avoided breaking the drive train, only to smash the cams. And I've also had people with the cams facing lever forward, which is great when the catch on something, and they ride with an open QR cam. By passing the lawyers lips, is difficult, but not impossible to achieve, and riding with a missing wheel, is tricky.


----------



## keithmac (11 Jun 2017)

I did A level Physics and Chemistry but can't remember either going into any detail about friction..

All interesting stuff!.


----------



## GrumpyGregry (11 Jun 2017)

As it happens I'm having tea with a professional industrial chemist/materials scientist and a genuine rocket scientist (two doctorates no less) later so I'm going to sound them out about the chemical reaction stuff.


----------



## Racing roadkill (11 Jun 2017)

winjim said:


> Nah. Hydrogen bonding, innit.


Which is the third type of vdW. Given it's a dipole-dipole interaction.


----------



## Racing roadkill (11 Jun 2017)

GrumpyGregry said:


> As it happens I'm having tea with a professional industrial chemist/materials scientist and a genuine rocket scientist (two doctorates no less) later so I'm going to sound them out about the chemical reaction stuff.


Be prepared for a lot of mathematics. And after several hours, the conclusion that tyre interactions are driven by mechanical interactions, and boosted / refined by chemical reactions.


----------



## Ming the Merciless (11 Jun 2017)

I've always put the tubes on the outside, is this wrong ?


----------



## HLaB (11 Jun 2017)

YukonBoy said:


> I've always put the tubes on the outside, is this wrong ?


Only if they are blue


----------



## Bollo (11 Jun 2017)

Yellow Saddle said:


> I can see a third option and that depends where in the vessel you are detecting for the two elements.
> Henceforth, can we please allow all arguments to stand on their own legs and speak for themselves and not be bolstered by framed certificates on the wall?


TBH, this thread is a clusterfunk and I've been out enjoying the Winchester Criterium today rather than keyboard warrioring. I brought up my qualifications because this is the second time I believe that Roadkill has asked me to get an education rather than addressing any arguments I've made on its merits. So I think my qualifications are firmly in play. It's not for you to say otherwise.
To answer the first part of the question, I did say it was a thought experiment - you know - cats in boxes and all. I put it out there to examine the arguments and it seems to have worked on that level at least.
My continuing issue with many of Roadkill's posts is that he claims expertise in so many fields both cycling and non-cycling related, yet constantly fails to back them up with anything remotely concrete. We're either expected to accept his word as infallible or follow some vague instructions to "look it up", usually sauced with a personal jibe or insult. It grips my guano. I'll respect any argument made on it's merits (including this one) and I'm happy to back down if I'm wrong, but I need solid evidence, not chest-thumping and arrogance. That's how the scientific method works.


----------



## Dirk (11 Jun 2017)

TBH, this thread has had nothing to do with the OPs original post since about halfway down page 1.
The OPs only contribution was to start the thread..... no other input..... zilch.
We are now 232 posts in and the thread has veered so far off course as to be unrecognisable from the title.
Maybe @Moderators need to consider closing it?


----------



## S-Express (11 Jun 2017)

Bollo said:


> My continuing issue with many of Roadkill's posts is that he claims expertise in so many fields both cycling and non-cycling related, yet constantly fails to back them up with anything remotely concrete. We're either expected to accept his word as infallible or follow some vague instructions to "look it up", usually sauced with a personal jibe or insult.



My only problem with the above is that you are being too polite.


----------



## Yellow Saddle (11 Jun 2017)

Dirk said:


> TBH, this thread has had nothing to do with the OPs original post since about halfway down page 1.
> The OPs only contribution was to start the thread..... no other input..... zilch.
> We are now 232 posts in and the thread has veered so far off course as to be unrecognisable from the title.
> Maybe @Moderators need to consider closing it?



That will leave us what, a few threads to speculate about household cleaners, shopping for second-hand shoes and wallets, quizzes and RIPs of old actors.

Valid cycling issues are rigorously debated here and there are still a few threads hanging in the air. Let it run its course.


----------



## Dirk (11 Jun 2017)

Yellow Saddle said:


> That will leave us what, a few threads to speculate about household cleaners, shopping for second-hand shoes and wallets, quizzes and RIPs of old actors.
> 
> Valid cycling issues are rigorously debated here and there are still a few threads hanging in the air. Let it run its course.


You could always start another thread which was more relevant to the issues being discussed.


----------



## Yellow Saddle (11 Jun 2017)

Dirk said:


> You could always start another thread which was more relevant to the issues being discussed.



So could you. I'll stick with this one.

The development from directionality of tread through to water dispersion to friction to the mechanism of friction is valid. You'll see, it will make full circle and it will be shown that because of the way that adherent friction works, treads do not have to point in any specific direction at all because they are in fact superflous and counter-productive.


----------



## winjim (11 Jun 2017)

Yellow Saddle said:


> That will leave us what, a few threads to speculate about household cleaners, shopping for second-hand shoes and wallets, quizzes and RIPs of old actors.
> 
> Valid cycling issues are rigorously debated here and there are still a few threads hanging in the air. Let it run its course.


Quite right. It's _Cycle_*Chat*. We're chatting.


----------



## Racing roadkill (11 Jun 2017)

Bollo said:


> TBH, this thread is a clusterfunk and I've been out enjoying the Winchester Criterium today rather than keyboard warrioring. I brought up my qualifications because this is the second time I believe that Roadkill has asked me to get an education rather than addressing any arguments I've made on its merits. So I think my qualifications are firmly in play. It's not for you to say otherwise.
> To answer the first part of the question, I did say it was a thought experiment - you know - cats in boxes and all. I put it out there to examine the arguments and it seems to have worked on that level at least.
> My continuing issue with many of Roadkill's posts is that he claims expertise in so many fields both cycling and non-cycling related, yet constantly fails to back them up with anything remotely concrete. We're either expected to accept his word as infallible or follow some vague instructions to "look it up", usually sauced with a personal jibe or insult. It grips my guano. I'll respect any argument made on it's merits (including this one) and I'm happy to back down if I'm wrong, but I need solid evidence, not chest-thumping and arrogance. That's how the scientific method works.


That's a troll post right there. I've tried to give you the evidence you seem to want, the fact you seem to fail to understand it isn't my problem. You say you were at the Winchester Crit today, it's a shame I didn't know what you look like, I would have loved to come and speak to you, about tyres.


----------



## Racing roadkill (11 Jun 2017)

YukonBoy said:


> I've always put the tubes on the outside, is this wrong ?


You'd be better off doing that with Continental tyres.


----------



## S-Express (11 Jun 2017)

Racing roadkill said:


> That's a troll post right there



Second most ironic post of the day...


----------



## Dec66 (11 Jun 2017)

Can I just say my tyres are on the right way round now?

Took me two attempts with the rear, as ten minutes after my first effort I heard the sudden "pfffffffft" of a pinch flat.

Always the back one, isn't it? Just glad I'd degreased the cassette, chain and rear derailleur.


----------



## winjim (11 Jun 2017)

Racing roadkill said:


> Which is the third type of vdW. Given it's a dipole-dipole interaction.


What are the first two and who decided on the order?


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> What are the first two and who decided on the order?


It is too difficult to explain and besides, you have to be prepared for hours and hours of Euclidean maths. You are not up to it.


----------



## winjim (11 Jun 2017)

Yellow Saddle said:


> What other mechanisms do you propose? And to be clear, "road" is dry asphalt/cement.


Given that the road surface is not completely smooth, I would expect there to be some mechanical interlocking of the surfaces. Of course the effect of some of this will be merely to increase surface area and therefore increase the amount of VdW interactions, but I'm just suggesting that there are likely to be more complex effects than a simple smooth surface model would suggest.


----------



## winjim (11 Jun 2017)

Yellow Saddle said:


> It is too difficult to explain and besides, you have to be prepared for hours and hours of Euclidean maths. You are not up to it.


What's that quote about explaining things to your Grandma?


----------



## ufkacbln (11 Jun 2017)

Smokin Joe said:


> *Next week's hot topic:*
> 
> Tea, does the milk go in the cup first or last?
> 
> And does it matter which way you stir?



The tradition was that Europeans were unable to make china of sufficient quality to accept boiling water .... so milk was placed in to stop the cup breaking

Never understood why they didn't just use cold water... unless there was Ye Olde Marketing of Milk Guild who through a chain of pamphleteers made milk the preferred choice

Stirring is simple - depends on hemisphere


----------



## ufkacbln (11 Jun 2017)

As a thought

Would the Coriolis effect mean that the OP's tyres would have been the right way round.... if they lived-in Australia?


----------



## mjr (11 Jun 2017)

Ian H said:


> The footprint of a road tyre is smaller than any part of a car tyre between the sipes. So even at car speeds it's unlikely to aquaplane.
> 
> Tread on a bike tyre becomes useful off-tarmac.


Including tarmac covered in shoot, as is common in most countries.

I'm pretty sure you're wrong about car tyre distance between sipes but my road bike has 32s on and I'm not going to put the calipers on my car tyres. The bike's not going fast enough anyway.


----------



## smutchin (11 Jun 2017)

Racing roadkill said:


> You say you were at the Winchester Crit today, it's a shame I didn't know what you look like, I would have loved to come and speak to you, about tyres.



Shame it wasn't raining, you'd have been able to spot him easily - he'd have been the one aquaplaning about all over the shop on his slick tyres.


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> What's that quote about explaining things to your Grandma?


If she doesn't have a PhD you may as well tell her to shut up and go play bingo. It is not worth wasting good mathematics on her. Pearls before the sow or something like that.


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> Given that the road surface is not completely smooth, I would expect there to be some mechanical interlocking of the surfaces. Of course the effect of some of this will be merely to increase surface area and therefore increase the amount of VdW interactions, but I'm just suggesting that there are likely to be more complex effects than a simple smooth surface model would suggest.



None with static friction. However, once we have kinetic friction, then hysteresis plays a role too. Mechanical interlocking never plays a role unless the two surfaces are perfectly mated (like gears) and then we are relying on the shear strength of the softest material, not VdW. This is a digital thing. Either it meshes or it doesn't. There isn't a second-best interloper.


----------



## winjim (11 Jun 2017)

Yellow Saddle said:


> None with static friction. However, once we have kinetic friction, then hysteresis plays a role too. Mechanical interlocking never plays a role unless the two surfaces are perfectly mated (like gears) and then we are relying on the shear strength of the softest material, not VdW. This is a digital thing. Either it meshes or it doesn't. There isn't a second-best interloper.


Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?


----------



## ufkacbln (11 Jun 2017)

winjim said:


> Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?



I thought for a minute that this is how you get Brompton tyres, but realised that with a soft rubber it could be a problem with that theory

Can you get viagra for tyres


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?


No. Imagine a perfectly soft (conforms to every nook and cranny) but perfectly frictionless material. Now imagine whether or not it will "hook and mesh" with road irregularities and resist them enough to create friction.


----------



## Racing roadkill (11 Jun 2017)

winjim said:


> Given that the road surface is not completely smooth, I would expect there to be some mechanical interlocking of the surfaces. Of course the effect of some of this will be merely to increase surface area and therefore increase the amount of VdW interactions, but I'm just suggesting that there are likely to be more complex effects than a simple smooth surface model would suggest.


And you'd be right.


----------



## Racing roadkill (11 Jun 2017)

Cunobelin said:


> As a thought
> 
> Would the Coriolis effect mean that the OP's tyres would have been the right way round.... if they lived-in Australia?


Coriolis effect is a macro effect ( extremely large volumes of fluid are needed ) hence the stuff you sometimes hear about toilet flushes and sink draining being effected differently in either hemisphere aren't right.


----------



## Racing roadkill (11 Jun 2017)

winjim said:


> Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?


you're nearly there. The mechanical effect is providing a mating, the chemical effect is what seals the deal.


----------



## winjim (11 Jun 2017)

Racing roadkill said:


> you're nearly there. The mechanical effect is providing a mating, the chemical effect is what seals the deal.


That chemical effect that you couldn't bring yourself to explain?


----------



## Yellow Saddle (11 Jun 2017)

winjim said:


> Given that the tyre rubber is soft though, doesn't it deform in such a way as to provide that perfect mating?


Perhaps the best visible manifestation of VdW's that one can see and feel and comprehend is that of Gauge Blocks (Gage Blocks in the US).

These are pretty incredible. They are perfectly-machined steel blocks of a given dimension (usually one-inch or similar sizes and abut 15mm thick). They are used to calibrate engineering measurement tools. Their sides are optically perfect in smoothness but much smoother than the wavelengh of visible light. Visible light's wavelength is in the order of 700nm but these blocks are smooth in the single-digit nm scale. In other words, if you wring two of them together, they make such good contact that VdW's kicks in and sticks them together. You can stick enough of them together that way to make a stick of about 300mm long. It takes quite a force to break them apart - a force I'd estimate similar to breaking a very hard biscuit.

Lots of people say there's a trick and that because it is steel, there's some sort of magnetism involved. Enter the ceramic gauge block. Same thing.

Then people say yes but it is air pressure that keeps them together: Enter the vacuum chamber. 

They stick entirely through van der Waals. And if anyone tells you VdW only works between like molecules: Enter the ceramic/steel combo.

If ever you can play with them, try it. Most precision engineering shops will have a set. They have an interesting story too. They were first manufacturerd to sort out Ford's accuracy and callibration problems in the 1940s, IIRC. 60 year old gauge blocks sell on 3-bay for as much as a brand new set, if they were looked after.

If you can't get your hands on a set, there's always YouTube. Plenty of rednecks there fooling around with them.


----------



## winjim (12 Jun 2017)

Yellow Saddle said:


> Perhaps the best visible manifestation of VdW's that one can see and feel and comprehend is that of Gauge Blocks (Gage Blocks in the US).
> 
> These are pretty incredible. They are perfectly-machined steel blocks of a given dimension (usually one-inch or similar sizes and abut 15mm thick). They are used to calibrate engineering measurement tools. Their sides are optically perfect in smoothness but much smoother than the wavelengh of visible light. Visible light's wavelength is in the order of 700nm but these blocks are smooth in the single-digit nm scale. In other words, if you wring two of them together, they make such good contact that VdW's kicks in and sticks them together. You can stick enough of them together that way to make a stick of about 300mm long. It takes quite a force to break them apart - a force I'd estimate similar to breaking a very hard biscuit.
> 
> ...


That's going on the list of things to show my kid when she's a bit older.


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## ufkacbln (12 Jun 2017)

Racing roadkill said:


> Coriolis effect is a macro effect ( extremely large volumes of fluid are needed ) hence the stuff you sometimes hear about toilet flushes and sink draining being effected differently in either hemisphere aren't right.







Also affects weather formations


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## winjim (12 Jun 2017)

Yellow Saddle said:


> No. Imagine a perfectly soft (conforms to every nook and cranny) but perfectly frictionless material. Now imagine whether or not it will "hook and mesh" with road irregularities and resist them enough to create friction.


What I'm imagining is something like a leopard using its claws to climb a tree, with the sharp road surface digging in to the soft tyre. But I guess that would depend on the roughness of a particular piece of road.


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## Tanis8472 (12 Jun 2017)

Thats roads around here perfectly described LOL


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## Yellow Saddle (12 Jun 2017)

winjim said:


> What I'm imagining is something like a leopard using its claws to climb a tree, with the sharp road surface digging in to the soft tyre. But I guess that would depend on the roughness of a particular piece of road.



That's not what happens but most people find it difficult to comprehend. It is a bit of a mind bender. We've been brainwashed by (car) tyre adverts and the (psychologically chosen) shapes of treadblocks on car tyres and also to an extent of tractor tyres and their V-grooves. It is easy to get imaginary views of traction from that. You have to dismiss what you think you know and start from ground zero.

I find it useful to at first just examine just how how much friction a piece of rubber on something really smooth, like glass has. Take a pencil eraser and draw it over a window with a bit of downforce. You'll see there's plenty of friction already, no need for tiger claws. There's enough friction to break the rubber bonds and leave a streak of rubber behind. Now think about the enormous traction a train locomotive generates by rolling smooth wheels on smooth tracks. It is pure VdW amplified by massive downforce.

Now progress to my example in the post above. A (very) soft tyre on very rough road but zero friction between the two. Forget about physical penetration of the rough surface on the soft surface. That's clearly not what happens. Just think of the deformation of rubber on road micro roughness but with the complete absence of friction (adhesion). Imagine how the tyre will just spin over the roughness as it is torqued because it cannot grip.

Now progress to a view of the above example where the rubber conforms to all the nano-scopic irregularities in the road but with adherent forces between the two. The irregularities increase the surface area in a fractal manner, VdW builds up and voila! Traction. The beauty of VdW is that it is cumulative and unlimited. Press harder and more VdW points switch on. 

The argument presented above is only for one case of traction: A smooth tyre on asphalt. Once we ride on gravel, mud, ice and vegetation, the mode of traction changes. Then we rely on penetration of a (hard) tyre on a (soft) surface and the shear strength of the substrate. In other words, tread and something like your tiger-up-a-tree example.


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## GuyBoden (12 Jun 2017)

Dirk said:


> 14 pages and not a sign of the OP since the first post........


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## winjim (12 Jun 2017)




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## Smokin Joe (12 Jun 2017)

Well Guy, what have you learned?


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## ChrisEyles (12 Jun 2017)

There was a thread in the touring section about what tyres to use for JOGLE... I was tempted to say use the same tyres you would for LEJOG, just reverse them 

Refrained, but couldn't resist posting it here.


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## winjim (12 Jun 2017)

Yellow Saddle said:


> That's not what happens but most people find it difficult to comprehend. It is a bit of a mind bender. We've been brainwashed by (car) tyre adverts and the (psychologically chosen) shapes of treadblocks on car tyres and also to an extent of tractor tyres and their V-grooves. It is easy to get imaginary views of traction from that. You have to dismiss what you think you know and start from ground zero.
> 
> I find it useful to at first just examine just how how much friction a piece of rubber on something really smooth, like glass has. Take a pencil eraser and draw it over a window with a bit of downforce. You'll see there's plenty of friction already, no need for tiger claws. There's enough friction to break the rubber bonds and leave a streak of rubber behind. Now think about the enormous traction a train locomotive generates by rolling smooth wheels on smooth tracks. It is pure VdW amplified by massive downforce.
> 
> ...


OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.


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## raleighnut (12 Jun 2017)

winjim said:


> OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.



View: https://youtu.be/Bt4rCWZp6zk


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## Yellow Saddle (12 Jun 2017)

winjim said:


> OK, now go the other way. Imagine a road surface made entirely of spikes. A soft tyre will work on such a surface because the spikes will dig in to the rubber like the leopard's claws, no friction is necessary. Now gradually reduce the size of the spikes and smooth out the road surface. As you do that, the effect of the spikes digging in becomes less, and frictional VdW forces become more, until you reach a smooth surface like your glass, where all the traction is given by friction. So there will be a region of particular road roughness / tyre softness where both effects contribute to the overall grip.


I don't agree with your conclusion. Either we are riding on spikes or we are not. If you are riding on spikes, the fact that there is a VdW between the spike and the rubber is kinda irrelevant, or at most superflous. If the spikes are just denting the rubber, then we are relying on VdW. There could even be a hybrid scenario where the two are balanced so finely that traction is reliant on both.

I cannot envisage such as scenario since we never ride on stuff that routinely and cyclically penetrate our tyres.

Reverse the scenario where the tyre's spikes penetrate the road, then we have a real scenario. Here we are talking about knobbly tyres punching into the substrate and relying on the shear strength of the substrate for traction. Similar with ice and carbide spike tyres. The spikes enter the ice and we rely on the ice's shear strength to provide traction. The fact that there is a teensy bit of VdW between tyre and ice is kinda irrelevant.

Imaginary scenarios however, are not the reason for tread in tyres or, the pattern direction of tread in tyres. There is no known scenario where tyres have to have penetrating devices to ride on asphalt.

Van der Waal's is all around us, you just have to open your eyes to it. I don't know why the poor Dutchman doesn't get the recognition for his work that he deserves. They treat friction in high school physics like religion: it is because it is. Just shut up and say f-r-i-c-t-i-o-n. At university physics its gets the same glanced-over treatment Only in some specialist courses do they delve into it. Typically specialised branches of mechanical engineering.

I urge you to have a good look at gauge blocks. They're the most eye-opening scenario I can think of. Even if you just look at it on You Tube.

I once had the opportunity to live in a country where geckos were a plague. They used to shoot everywhere in the house, get in the toaster and make your toast smell like bacon, short out the television set by walking across wires, lay eggs in PC fans etc etc. I watched them for hours and hours walking on all sorts of surfaces I would fashion for them surfaces to hang from (vertical and inverted) that you can only imagine. Only if the surface was not strong (powdery, siliconised etc) could they not walk upside down. I had one clinging to a gauge block's polished surface in any orientation - no problem. They use VdW to their advantage, yet us humans still fart around with treads in tyres. They are not like an octopus wit suckers, they cling with little other than soft, good-contact hairs on their feet. All VdW.

I realise that science is not everyone's cup of tea but dammit man, how do you get people to take an interest in why and how things behave all around us like they do?

Go put a flat aluminium pan on your ceramic stove hob and pick it up. Feel the force. It is with you.

Rant (to no-one in particular) off.


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## winjim (12 Jun 2017)

Yellow Saddle said:


> I don't agree with your conclusion. Either we are riding or spikes or we are not. If you are riding on spikes, the fact that there is a VdW between the spike and the rubber is kinda irrelevant, or at most superflous. If the spikes are just denting the rubber, then we are relying on VdW. There could even be a hybrid scenario where the two are balanced so finely that traction is reliant on both.
> 
> I cannot envisage such as scenario since we never ride on stuff that routinely and cyclically penetrate our tyres.
> 
> ...


VdW forces do seem to be taught more in chemistry than in physics, mainly to explain what liquids and solutions are.

As for the science education bit, you know how people get annoyed with their kids constantly asking "why"? I have resolved never to do that. It is the most important question of all. Children are natural scientists, I intend to try and keep that enthusiasm going for as long as possible.

For what it's worth, I am not suggesting that the mechanical interlocking / spiky effect is, in road conditions, dominant or even particularly large compared to the VdW forces, just that it makes _some_, however minor, contribution. With you on the tread, although I still can't bring myself to put those little arrows on the wrong way. Maybe one day I should, it might be quite a liberating experience.


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## Ajax Bay (12 Jun 2017)

winjim said:


> I still can't bring myself to put those little arrows on the wrong way.


Whilst it's obvious  that the front wheel should be mounted so the arrow points in the direction of rotation, surely the tyre on the rear wheel should be mounted the other way round. Leaving aside cornering, the grip of the front tyre is used for braking whereas the limiting factor for the rear tyre is not braking but the absolute need to have enough grip for climbing a steep hill out of the saddle on a surface made slippery by the conditions.


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## Yellow Saddle (12 Jun 2017)

winjim said:


> . With you on the tread, although I still can't bring myself to put those little arrows on the wrong way. Maybe one day I should, it might be quite a liberating experience.



There's a thread here right now about phobias. Go and report yours - arrowpointingbackwardsaphobia.


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## nickyboy (12 Jun 2017)

I know nothing about VdW forces but a quick wiki suggests one of them is known as "London Dispersion Forces" which I had previously assumed was a synonym for the Metropolitan Police


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## GrumpyGregry (12 Jun 2017)

Gauge blocks... but the thing is if you were to force them into even closer proximity the atomic forces repel each other. I'm not really sat in this chair... the atoms in my arse are being repelled by the atoms in the chair... else I'd merge into the chair.


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## winjim (12 Jun 2017)

nickyboy said:


> I know nothing about VdW forces but a quick wiki suggests one of them is known as "London Dispersion Forces" which I had previously assumed was a synonym for the Metropolitan Police


I think it's Boris' water cannon.


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## Alan O (12 Jun 2017)

GrumpyGregry said:


> I'm not really sat in this chair... the atoms in my arse are being repelled by the atoms in the chair... else I'd merge into the chair.



“The gross and net result of it is that people who spent most of their natural lives riding iron bicycles over the rocky roadsteads of this parish get their personalities mixed up with the personalities of their bicycle as a result of the interchanging of the atoms of each of them and you would be surprised at the number of people in these parts who are nearly half people and half bicycles...when a man lets things go so far that he is more than half a bicycle, you will not see him so much because he spends a lot of his time leaning with one elbow on walls or standing propped by one foot at kerbstones.”
― Flann O'Brien, The Third Policeman


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## Alan O (14 Jun 2017)

Dogtrousers said:


> @AlanO über-like


It's a great book.


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## Gravity Aided (16 Jun 2017)

Highly recommended, DeSelby enjoyed it immensely, in his time.


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## smutchin (16 Jun 2017)

Alan O said:


> It's a great book.



Essential reading for anyone participating in this thread. Or indeed anyone at all.


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## SWSteve (16 Jun 2017)

Vegan1 said:


> And what about grip?




Tell Valentino Rossi that he needs treaded tyres to go fast.


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## atalanta (16 Jun 2017)

smutchin said:


> Essential reading for anyone participating in this thread. Or indeed anyone at all.


Is it as mad as Swim-Two-Birds? I bloody loved that but it was hard work.


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## SWSteve (16 Jun 2017)

Racing roadkill said:


> The 'nd' figure ( stress corrosion coefficients) are different. The front tyre is designed to cope with more deformations ( due to steering trail, as well as the accelerations that the rear is subject to). The front tyre should have a higher 'nd' than the rear tyre. Again it's casting pearls before swine, for the most part, but if you know what you're doing, the difference, should be advantageous.




Im pretty sure Pearls before Seine used to be in the metro


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## Alan O (16 Jun 2017)

atalanta said:


> Is it as mad as Swim-Two-Birds? I bloody loved that but it was hard work.


I'd say it's a lot less challenging.

Oh, and don't read the Wikipedia article, as it's a book best read from a position of not knowing anything about it - I first read it when a friend handed me his copy and said "Just read it".


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## smutchin (17 Jun 2017)

atalanta said:


> Is it as mad as Swim-Two-Birds? I bloody loved that but it was hard work.



Don't know, I've never read it. I really ought to though. 

Interesting coincidence, Brendan Gleeson was on Kermode & Mayo's R5 prog yesterday and mentioned that he had a long-term project to make a film of At Swim-Two-Birds - but don't hold your breath...


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## Ming the Merciless (17 Jun 2017)

Does the valve need to fast the inside or outside of the wheel?


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## riddly (18 Dec 2018)

I just took delivery of a hybrid bike with the tyres on both ways - front chevron facing backwards.
Obviously that’s unlucky, as that’s the tyre that hit the blackthorn after 30 miles.. six bloody punctures.
So much for Kevlar, they’re both facing forward now.


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## riddly (19 Dec 2018)

Flick of the Elbow said:


> I've never paid any notice of those arrows. As you say, no discernible difference, not for a road tyre anyway. I imagine it would make a difference on a tyre designed for mud.


Don’t mud tyres have non-directional knobbles?


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## Red17 (20 Dec 2018)

Not all. I run Challenge Limus tyres on my cx bike which Challenge website say are directional (the knobs are arrow shaped rather than square)


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## Globalti (20 Dec 2018)

It's all cobblers dreamed up by marketing types in an effort to add value to their tyres. The only possible reason for a direction arrow is to ensure that the brand name of the tyre goes where it should be, on the right. Some tyres, Veloflex for example, only have the name on one side.


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## Globalti (20 Dec 2018)

That goes without saying!


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## Racing roadkill (20 Dec 2018)

There is a purpose to having tyres with ‘tread’ on the shoulders ( it’s not tread, it’s not there to enhance grip, or move water ) with the arrow pointing in the correct direction. It’s there to make sure that the manufacturers ‘power’ spec is applicable. The Q.A. compliance people don’t like it if a tyre’s spec can’t be matched in the real world. The ‘tread’ is an aerodynamic / fluid dynamic device, to ensure any aero drag caused by the tyre is minimised. Air against air / water against water is less draggy than rubber against air, or rubber against water, so the ‘tread’ is there to trap air / water as the tyre rotates, which reduces drag, and gives the manufacturer something which helps them ‘prove’ their figures. With a slick tyre the arrow points so that the tyre rolls in the direction that the tread was laid onto the carcass. The boundary between the carcass and the tread is not actually perfectly uniformly flat, it’s ever so slightly ‘pear shaped’, in order to keep the tyres performance as ‘per spec’ the tyre should roll from the bulb to the tail, on each rotation ( this is also the case with ‘patterned / treaded tyres, but the pattern overrides the tread / carcass interface issue with patterned tyres) All of this is of little real world consequence, but compliance / Q.A. are a pain in the butt, and need stuff like this to keep them quiet.


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## Globalti (20 Dec 2018)

Sorry... could you repeat that for me?


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## raleighnut (20 Dec 2018)

Globalti said:


> Sorry... could you repeat that for me?



I think he's saying that it has the same effect as the dimples on a golfball, the 'port' on my speakers is dimpled for a similar reason.


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## Globalti (20 Dec 2018)

So at 20 mph a small part of your tyres is hitting the air at 40 mph? And they are trying to make them aerodynamic?


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## raleighnut (20 Dec 2018)

Globalti said:


> So at 20 mph a small part of your tyres is hitting the air at 40 mph? And they are trying to make them aerodynamic?


The diametrically opposite part of the tyre is actually stationary.



Spoiler



It's in firm contact with the ground unless you're skidding


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## Ajax Bay (20 Dec 2018)

raleighnut said:


> it has the same effect as the dimples on a golfball


There is a good deal of quality science and practical testing behind the benefit of dimples on a golf ball. Less (vanishingly less) behind the 'come again' post above. 
"the manufacturers ‘power’ spec" - examples?
"the ‘tread’ . . . gives the manufacturer something which helps them ‘prove’ their figures." Assume these figures are the aforementioned ‘power’ spec figures.


Globalti said:


> So at 20 mph a small part of your tyres is hitting the air at 40 mph? And they are trying to make them aerodynamic?


The top of the front tyre is moving at 40mph but not sure there's any "trying" going on (see quote below). Why not make them as aerodynamic as possible? The best way to do this is to have an 'overhanging' mudguard (I have read) - not UCI legal, I suspect. 
From the mag in 2017:
"According to Continental, the aerodynamics of the GP4000 “wasn’t a design feature, but the shape is good and the tread gives micro turbulence as a 23mm on a wider rim”. It would appear that the observed aerodynamic prowess of the Continental GP4000 is down to serendipity."
If the patterns (as rr says (truth smuggled in) "it’s not tread, it’s not there to enhance grip, or move water") on the Continental tyre shoulders have any aero effect (delaying the transition from laminar to turbulent air flow), I suggest they will work just as well which ever way round the tyre is fitted. I wish there was well-founded research on this but yet to find anything (I have looked).


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## Blue Hills (20 Dec 2018)

Globalti said:


> Sorry... could you repeat that for me?


With paragraphs as well.


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## Heltor Chasca (20 Dec 2018)

I think my cerebral cortex must be on the wrong way round. I can’t function after reading this.


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## Yellow Saddle (23 Dec 2018)

Racing roadkill said:


> There is a purpose to having tyres with ‘tread’ on the shoulders ( it’s not tread, it’s not there to enhance grip, or move water ) with the arrow pointing in the correct direction. It’s there to make sure that the manufacturers ‘power’ spec is applicable. The Q.A. compliance people don’t like it if a tyre’s spec can’t be matched in the real world. The ‘tread’ is an aerodynamic / fluid dynamic device, to ensure any aero drag caused by the tyre is minimised. Air against air / water against water is less draggy than rubber against air, or rubber against water, so the ‘tread’ is there to trap air / water as the tyre rotates, which reduces drag, and gives the manufacturer something which helps them ‘prove’ their figures. With a slick tyre the arrow points so that the tyre rolls in the direction that the tread was laid onto the carcass. The boundary between the carcass and the tread is not actually perfectly uniformly flat, it’s ever so slightly ‘pear shaped’, in order to keep the tyres performance as ‘per spec’ the tyre should roll from the bulb to the tail, on each rotation ( this is also the case with ‘patterned / treaded tyres, but the pattern overrides the tread / carcass interface issue with patterned tyres) All of this is of little real world consequence, but compliance / Q.A. are a pain in the butt, and need stuff like this to keep them quiet.



Barman! I'll have some of what this chap is drinking.


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## Ming the Merciless (23 Dec 2018)

Racing roadkill said:


> There is a purpose to having tyres with ‘tread’ on the shoulders ( it’s not tread, it’s not there to enhance grip, or move water ) with the arrow pointing in the correct direction. It’s there to make sure that the manufacturers ‘power’ spec is applicable. The Q.A. compliance people don’t like it if a tyre’s spec can’t be matched in the real world. The ‘tread’ is an aerodynamic / fluid dynamic device, to ensure any aero drag caused by the tyre is minimised. Air against air / water against water is less draggy than rubber against air, or rubber against water, so the ‘tread’ is there to trap air / water as the tyre rotates, which reduces drag, and gives the manufacturer something which helps them ‘prove’ their figures. With a slick tyre the arrow points so that the tyre rolls in the direction that the tread was laid onto the carcass. The boundary between the carcass and the tread is not actually perfectly uniformly flat, it’s ever so slightly ‘pear shaped’, in order to keep the tyres performance as ‘per spec’ the tyre should roll from the bulb to the tail, on each rotation ( this is also the case with ‘patterned / treaded tyres, but the pattern overrides the tread / carcass interface issue with patterned tyres) All of this is of little real world consequence, but compliance / Q.A. are a pain in the butt, and need stuff like this to keep them quiet.



So by having tyres on the wrong way round the fabric of space time is unravelling or have I misunderstood?


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## Racing roadkill (23 Dec 2018)

YukonBoy said:


> So by having tyres on the wrong way round the fabric of space time is unravelling or have I misunderstood?


Yes you clearly need to re think your life.


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## Racing roadkill (23 Dec 2018)

Globalti said:


> Sorry... could you repeat that for me?




https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/

This is the same effect, but on golf balls.


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## Racing roadkill (23 Dec 2018)

raleighnut said:


> I think he's saying that it has the same effect as the dimples on a golfball, the 'port' on my speakers is dimpled for a similar reason.


That’s not far off.


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## Racing roadkill (23 Dec 2018)

Globalti said:


> So at 20 mph a small part of your tyres is hitting the air at 40 mph? And they are trying to make them aerodynamic?


Pretty much. “Trying” being the operative word.


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## Ajax Bay (23 Dec 2018)

Yellow Saddle said:


> Barman! I'll have some of what this chap is drinking.


Pretty sure he has you on ignore (or he is exhibiting restraint the like of which we have not yet seen), and you're not the only one. Have a great 'Kintyre' Hogmanay.


Racing roadkill said:


> “Trying” being the operative word.


Not even sure if they're "trying". Serendipity not design.
"the ‘tread’ is there to trap water as the tyre rotates"  What speed, compared to the road surface, is the "trapped" water travelling at? Will H2O's Reynolds Number be approached?


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## Ian H (23 Dec 2018)

I read somewhere that the only reasons for tread patterns on road tyres were, a) brand recognition and, b) because many riders were instinctively reassured by it.


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## winjim (23 Dec 2018)

Racing roadkill said:


> There is a purpose to having tyres with ‘tread’ on the shoulders ( it’s not tread, it’s not there to enhance grip, or move water ) with the arrow pointing in the correct direction. It’s there to make sure that the manufacturers ‘power’ spec is applicable. The Q.A. compliance people don’t like it if a tyre’s spec can’t be matched in the real world. The ‘tread’ is an aerodynamic / fluid dynamic device, to ensure any aero drag caused by the tyre is minimised. Air against air / water against water is less draggy than rubber against air, or rubber against water, so the ‘tread’ is there to trap air / water as the tyre rotates, which reduces drag, and gives the manufacturer something which helps them ‘prove’ their figures. With a slick tyre the arrow points so that the tyre rolls in the direction that the tread was laid onto the carcass. The boundary between the carcass and the tread is not actually perfectly uniformly flat, it’s ever so slightly ‘pear shaped’, in order to keep the tyres performance as ‘per spec’ the tyre should roll from the bulb to the tail, on each rotation ( this is also the case with ‘patterned / treaded tyres, but the pattern overrides the tread / carcass interface issue with patterned tyres) All of this is of little real world consequence, but compliance / Q.A. are a pain in the butt, and need stuff like this to keep them quiet.


I have questions. What is "'power' spec", how is it defined and how is it measured?


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## Racing roadkill (24 Dec 2018)

winjim said:


> I have questions. What is "'power' spec", how is it defined and how is it measured?


It’s power loss difference compared to a standard. Measured in Watts. They run a tyre with an agreed size, shape, design and composition at a certain speed, in agreed standard conditions, for an agreed standard time. Then work out the power required to do so. Then run their comparison tyre in the same conditions and compare results. It’s not an industry standard test, there is no regulatory requirement to have the figures, so they can only state comparisons between tyres. There are tables of results, in cycling publications where tyres are tested for relative power loss. The tyre manufacturers often have their own internal specs as well.


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## Justinslow (24 Dec 2018)

Just read this whole thread.....

And we wonder why the powers that be can’t sort out Brexit.


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