Directional tread pattern

[Matthew_T]

Only if the tyre has deep cleats will it make any difference off road. The tread of a road bike tyre is unnecessary (at best) on the road and useless off it.

Is that why Conti GP4's dont have any tread and yet loads of people say they are good in all conditions?

 

[Norm]

Probably - although construction (compound used, stiffness, shape etc) will also make a difference. The thing that tread does on a road tyre is reduce the amount of tyre in contact with the road and, possibly, reduces the stability and strength of the rubber which is in contact with the road.

 

[al78]

You still have a lot to learn young man.
Slicks are better in the wet then tyres with tread as there is more contact with the road.
And as for aquaplaning...see Mr P's post above.

I understood this to be true but in another thread someone suggested that narrow slick tyres are better in the wet than wide slick tyres. This seems counter-intuitive based on the "more rubber in contact with the road" theory as a wide tyre will have a greater footprint than a narrow tyre (as they are run at a lower pressure), and thus will have more rubber in contact with the road. It was suggested that the narrow tyre cuts through the surface water better but surely this is only an issue if aquaplaning is a significant risk which it isn't with bicycles.

 

[Norm]

I understood this to be true but in another thread someone suggested that narrow slick tyres are better in the wet than wide slick tyres.

Maybe you should address that in the other thread, where the person who suggested that can suggest why it might be the case, IMO, on a wet road, wider tyres generally give better traction for a cyclist.

 

[fossyant]

Rubber compound is important for road tyres. Tread pattern is important for MTB's depending upon riding conditions - mud, hard pack trails etc.. Directional tyres - make a very slight difference - you would be hard pushed to tell. Many performance MTB tyres are front or rear only. On hybrids etc, I doubt you'd notice the tread direction. Riding the MTB through heavy mud/loose stone, then yes, but that's at the extremes.

 

[Davidc]

On hard surfaces ianrauk and User have said it all. For an explanation ask someone doing A Level applied maths, who should also be able to explain the effect of contact area.

On thick mud there's an effect often referred to as keying. The mud is moulded to a pattern to complement the tyre, and if it's viscous enough it helps with grip. I have seen a mathematical analysis of this, but it related to tyres on tractors and other big machines. There may be one for bikes, and that would give the limits over which treaded tyres and perhaps knobblies have an effect.

 

[Bodhbh]

I rode with some of mine the wrong way round for a few months. The bike was upside-down when changing tyres, I had a brainfart between right, left, down and up. I think the main hazard is encountering some numpty that will feel obliged to point out your mistake.

I did wonder how the direction of chevron pattern effected braking in mud tho.

 

[Ajax Bay]

The importance of tread pattern on cycle tyres

On surfaces that will move under your tyre eg mud, some tread is useful. But on asphalt/tarmac/road the tyre 'moulds' to the road surface. Cycle tyres will not aquaplane (see link below) and any tread will merely serve to reduce the rubber in contact with the road and therefore reduce grip. Given the forces involved it is unlikely that there will be any performance merit or loss whichever way round tyres are mounted, irrespective of 'drive arrow' markings. The latter have been put there, much as the tread has, to meet customers' expectations, and possibly for aesthetic reasons (to avoid the 'look he's put the tyres on back-to-front' comments from the incognoscenti).

To explore and seek a few figures:
For a given rider, bike and any load, the total mass will be supported by the contact area x pressure (both tyres) irrespective of the width of or circumference of the tyre. The wider the tyre (for given pressure and load) the 'shorter' the contact area ellipse. So for example on 28mm tyres the loaded contact patch is circa 20mm wide. If the total load is 100kg, split 40/60 (front/rear) and tyre pressures are 70psi and 105 psi, then the contact area for each tyre is ~8cm2 and this ellipse is 2cm wide and about 5cm long. If you ran them at the same pressures (you wouldn't) the contact area of a wide tyre eg 2+" would be almost a circle.

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

 

[Yellow Saddle]

Physics suggests that the direction arrows should be reversed on front wheels, so you had them right before.

What physics would that be?

 

[Yellow Saddle]

I was told it is not so much to do with the tread pattern (if any) on a slick road tyre, but relates to the construction of the tyre casing.

Yes to the first, no to the second.
The casing is perfectly symmetrical. There is no difference between right way and also right way round. The exception is on some MTB tyres with aggressive knobblies which have been chamfered at their leading edges. If you reverse these tyres they are very noisy for a while. Withing a hundred kms or so on asphalt they have self re-engineered themselves to have chamfered leading edges....and trailing edges and are silent.

 

[Citius]

The trouble with directional arrows on tyres - is that they are always travelling in the wrong direction 50% of the time..

 

[Yellow Saddle]

The importance of tread pattern on cycle tyres

On surfaces that will move under your tyre eg mud, some tread is useful. But on asphalt/tarmac/road the tyre 'moulds' to the road surface. Cycle tyres will not aquaplane (see link below) and any tread will merely serve to reduce the rubber in contact with the road and therefore reduce grip. Given the forces involved it is unlikely that there will be any performance merit or loss whichever way round tyres are mounted, irrespective of 'drive arrow' markings. The latter have been put there, much as the tread has, to meet customers' expectations, and possibly for aesthetic reasons (to avoid the 'look he's put the tyres on back-to-front' comments from the incognoscenti).

To explore and seek a few figures:
For a given rider, bike and any load, the total mass will be supported by the contact area x pressure (both tyres) irrespective of the width of or circumference of the tyre. The wider the tyre (for given pressure and load) the 'shorter' the contact area ellipse. So for example on 28mm tyres the loaded contact patch is circa 20mm wide. If the total load is 100kg, split 40/60 (front/rear) and tyre pressures are 70psi and 105 psi, then the contact area for each tyre is ~8cm2 and this ellipse is 2cm wide and about 5cm long. If you ran them at the same pressures (you wouldn't) the contact area of a wide tyre eg 2+" would be almost a circle.

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

The message is correct, but the physics flawed. I have highlighted the errors in bold. The error here is the notion that reduced contact area reduces grip. The amount of grip remains the same, irrespective of the contact area, if the other variables (rubber type and downforce) remains the same. The co-efficient of friction issue doesn't care about surface area.

Deep tread, especially on mountain bikes where a deep tread implies smaller knobs, do tend to wander when cornering. This is because the knobblies bend sideways during cornering and the knobblies effectively walk off the steered arc.

 

[Yellow Saddle]

I understood this to be true but in another thread someone suggested that narrow slick tyres are better in the wet than wide slick tyres. This seems counter-intuitive based on the "more rubber in contact with the road" theory as a wide tyre will have a greater footprint than a narrow tyre (as they are run at a lower pressure), and thus will have more rubber in contact with the road. It was suggested that the narrow tyre cuts through the surface water better but surely this is only an issue if aquaplaning is a significant risk which it isn't with bicycles.

You are right in that aquaplaning is not a risk with bicycles at all, nor with aeroplanes or motorcycles - all which have tubular tyres. The rounded profile make them boat-shaped. If you look at the contact patch, you will see this. This shape is a natural water disperser. A car tyre on the other hand has a square contact patch and does not disperse water as well, hence the requirement for siping grooves.

 

[Ajax Bay]

Along the line of the cycle's axis, the contact area of both the rear and the front tyres have to contend with frictional forces associated with braking (limit = skid), whereas the contact area of the rear tyre has also to contend with force in the opposite direction, and the limiting expression of this is when the tyre 'slips' during peak load, invariably up hill on a surface which has a lower than normal coefficient of friction. Whatever; on road, tread makes no difference.

The amount of grip remains the same, irrespective of the contact area,

Thank you for correcting me. The normal force remains the same as does the coefficient of friction (given rubber type and road surface) so the 'grip' stays the same, even if the tread pattern has effectively reduced the area actually in contact with the ground. Though presumably there is a limiting point as the tyre pressure is increased, perhaps to do with bouncing (ie tyre momentarily lightening/losing contact with the ground).

 

[Yellow Saddle]

I didn't see the date. Thanks.

You are wasting your time. Norm is, alas, long departed.

I didn't see the date, thanks.