24mm vs 22mm

[migrantwing]

I'm running Durano S on the front and Durano Plus on the back, both 23mm. Will try 25's next, just to see if there's any difference at all.

 

[Tojo]

Yes: a more relevant diagram would have shown the contact areas when both tyres were pumped up to to the middle pressure of their recommend pressure range.

Well, here you go I'm resurrecting this thread, after you slagged of my findings......have a look here,
http://road.cc/content/feature/153488-trend-spotting-why-you-need-switch-wider-tyres
The whole of the TDF riders are going this way, as I think their research is probably a bit more intense than your average club racing findings......

And.....I've just measured (with a micrometer) my 23mm Conti GP4000sII's and they are in fact 24.85mm wide....

 

[mustang1]

I call BS on the low rolling resistance theory of wider tires (PS I'm not a physics major).

This is how its marketed: narrow tire A and wide tire B are compared. To make things equal (and this is where they fool you by claiming equality), they say both are pumped to 80psi and at this pressure, the narrow tire deforms more. This is true.

BUT the narrow tire isn't supposed to be pumped to 80psi, but 120psi, and at that pressure, the narrow tire does not deform as much as the wider tire. In fact I would say it offers less rolling resistance, since it is also narrower.

NOT only that, but when considering a wider tire, not only should you look at the cross section of the tire as someone posted a Conti diagram above, but you also need to review how wide the tire is and does it deform laterally as well.

Having said that, many years ago I moved from 23 to 25mm tires because I got less flats with the latter. I also have a bike with 35mm tires and while we can discuss a bunch of other variables, I know the 35mm tire bike is way slower and less accelerative than the skinnier tire'd bike.

I'm not sure if the following are comparable, but why don't electric cars have wide tires if they offer less rolling resistance? Or are you only supposed to go as wide up to a certain point as determined by engineering. Or marketing? Maybe in 10 years time the marketing department will dictate you all go and buy narrower, or wider tires, due to 'evidence' (as researched, and funded, by TIRE MANUFACTURERS!)

All the above is for road surfaces, not MTB.

 

[Drago]

I noticed a lot of TDF riders on 700C x 2.1 this year.

Not.

 

[Citius]

BUT the narrow tire isn't supposed to be pumped to 80psi, but 120psi, and at that pressure, the narrow tire does not deform as much as the wider tire. In fact I would say it offers less rolling resistance, since it is also narrower.

Who says the narrower tyre should be inflated to 120psi?

I'm not sure if the following are comparable, but why don't electric cars have wide tires if they offer less rolling resistance?

Because car tyres are of a different construction, there are four of them and the dynamic forces on them are completely different. The two simply cannot be compared.

 

[Tojo]

According to Continental, a 20mm tyre with 160psi, a 23mm tyre at 123psi, a 25mm tyre at 94psi and a 28mm tyre at 80psi all have the same rolling resistance.....

 

[mustang1]

Who says the narrower tyre should be inflated to 120psi?

Because car tyres are of a different construction, there are four of them and the dynamic forces on them are completely different. The two simply cannot be compared.

What I mean is the narrower tire should be inflated to a higher pressure than the wider one. In my mind I was comparing a 25mm with 35mm, but didn't want to state specific widths, just keep the numbers generic.

Ps: yes you are right about car tires.

 

[Citius]

What I mean is the narrower tire should be inflated to a higher pressure than the wider one. In my mind I was comparing a 25mm with 35mm, but didn't want to state specific widths, just keep the numbers generic.

You're missing the point somewhat. Which is that for a given pressure, a higher volume tyre will typically roll better.

 

[mustang1]

You're missing the point somewhat. Which is that for a given pressure, a higher volume tyre will typically roll better.

I dont get it. Do you mean if the lower volume tire is pumped to X psi, and a larger volume tire is also pumped to X psi, the wider tire will roll better?

 

[Citius]

Bingo.

 

[mustang1]

Bingo.

No dice. Why would you pump the narrower tire to the same psi as the wider tire?

 

[Citius]

No dice. Why would you pump the narrower tire to the same psi as the wider tire?

In order to compare them in a way that means something.

 

[Yellow Saddle]

I'm running Durano S on the front and Durano Plus on the back, both 23mm. Will try 25's next, just to see if there's any difference at all.

How would you measure the difference?

 

[mustang1]

In order to compare them in a way that means something.

Well, as an example if I had a 35mm tire at 80psi and compared it to a 25mm tire at 80psi, then perhaps the wider tire would have better rolling resistance. But I would NEVER ride a 25mm tire at just 80psi even if it does make a great theoretical lab experiment.

Out on the road, I'd pump the narrower tire far higher than the wider tire. Doesn't that mean something?

 

[Yellow Saddle]

I call BS on the low rolling resistance theory of wider tires (PS I'm not a physics major).

If physics is not your thing, why call BS when you could instead ask how it works?
It is not BS.

This is how its marketed: narrow tire A and wide tire B are compared. To make things equal (and this is where they fool you by claiming equality), they say both are pumped to 80psi and at this pressure, the narrow tire deforms more. This is true.
BUT the narrow tire isn't supposed to be pumped to 80psi, but 120psi, and at that pressure, the narrow tire does not deform as much as the wider tire. In fact I would say it offers less rolling resistance, since it is also narrower.

Your assumption is that rolling resistance comes from the formation of the air cushion in the tyre. That is not where rolling resistance comes from.

NOT only that, but when considering a wider tire, not only should you look at the cross section of the tire as someone posted a Conti diagram above, but you also need to review how wide the tire is and does it deform laterally as well.

A tyre is essentially a tubular cylinder and therefore its cross section is its width.

Having said that, many years ago I moved from 23 to 25mm tires because I got less flats with the latter. I also have a bike with 35mm tires and while we can discuss a bunch of other variables, I know the 35mm tire bike is way slower and less accelerative than the skinnier tire'd bike.

How did you determine that you got less flats from one width than the other? You make it sound like it is a fact that the one width is less prone to flats than the other. The assumption of course derived from your statement is that the type of flats you got were due to intrusion punctures not pinch flats, otherwise could simply have upped the air pressure to avoid those.

I'm not sure if the following are comparable, but why don't electric cars have wide tires if they offer less rolling resistance? Or are you only supposed to go as wide up to a certain point as determined by engineering. Or marketing? Maybe in 10 years time the marketing department will dictate you all go and buy narrower, or wider tires, due to 'evidence' (as researched, and funded, by TIRE MANUFACTURERS!)

They are not comparable. Besides, what do electric cars have to do with it?

All the above is for road surfaces, not MTB.

Measuring rolling resistance has nothing to do with surface. It is measured on a smooth steel drum and additional "events" such as rocks or mud or surface texture is simply an overlay on the base measurement. Your statements are equally BS for road or rough.