affects of tyre width on speed

[tubbylee]

im thinking of changing the tyres on my sirrus elite from 28c to 23c,the tyres i have are specialised all condition tyres and have never let me down.im competing in a duathlon in a months time and ive been told by collegues 23c would make a big difference on my speed is this true,i would be looking to use a similar type of puncture resistant tyre,as a flat in the middle of the race would be of no benefit.any advice would be appechiated thankyou

 

[Rouge Penguin]

The biggest difference would be comfort. I run 25s and wouldn't bother going to 23.

 

[Rouge Penguin]

Let me quantify that. I wouldnt because of one event, it wouldn't outweigh the rest of the longer rides. Work on your average speeds to be quicker.

 

[Paulus]

As a gereral rule, the wider the tyre the more rolling resistance it creates, as there is more rubber in contact with the road. So going down a size or two should speed your ride up a bit, but you will notice a bit more road vibration as there is less rubber. I run 25's on my bikes, except the tourer which has 28's and they are still pretty comfortable.

 

[BSRU]

As a gereral rule, the wider the tyre the more rolling resistance it creates, as there is more rubber in contact with the road. So going down a size or two should speed your ride up a bit, but you will notice a bit more road vibration as there is less rubber. I run 25's on my bikes, except the tourer which has 28's and they are still pretty comfortable.

Wasn't there some research lately that suggested bigger tyres had lower rolling resistance due not deforming as much as thinner tyres. Thinner tyres were better aerodynamically, i.e. less wind resistance.

 

[gbb]

Reading Zinns Art of Roadbike Maintenance the other day opened my eyes to this issue. He stated that tyre width doesn't neccessarily make that much difference to speed, its the side wall, more importantly the strength of that side wall, that makes the difference. His opinion was that many 25mm tyres would be just as good as 23mm's.
Mind, the difference from 28 to 23 must have an impact...surely ?

 

[Rob3rt]

Someone posted a scientific study on here somewhere not long ago that basically claimed to debunk the tyre width's effect on rolling resistance (whether results are noteworthy or not I dont know). Thus increased emphasis should be paid to the deflection of the tyre and thus tyre pressure, compound and sidewall strength rule the day.

 

[frank9755]

Narrower tyres are faster not mainly because they are narrower but because they can be run at higher pressures. Higher pressure means less deformation of the sidewall and associated energy loss.

As others mention, there are other factors involved such as the type of compound and how it deforms. Tyres with better puncture resistance are generally slower. For example, Marathon Plus tyres are noticeably slower than ordinary Marathons of the same size.

If you are racing then 23s would be sensible. They will be faster than 28s (not because they are narrower but because you will run them at c120psi rather than c100 so they will deform less). Then you have to decide what trade-off you want to make between a fast compound and puncture resistance.

Here's a good summary of options!

 

[HLaB]

According to lab tests if tyres are pumped up, the wider tyres will actually roll better but try telling that to Wiggins, Cavendish et al. I think they are on 23mm.

On a persosal note my Kinesis used to have a 23 front/ 25 rear combo; when the 25 wore out the 23 was moved to the rear and a new 23 went on the front I've noticed little if any difference. I also changed the 28's for 25's on the Sirrus I found that made a more noticeable difference without too harsh a ride but how much of it was to do with me getting fitter and other mods (new wheels, drop bars & carbon seatpost) I couldn't quantify. Probably others will have other opinions but I think 25mm are the best compromise for comfort/speed.

 

[PpPete]

Rather depends whether you want one set of tyres for day to day use, and a different set for racing....

Single set for everything - I'd definitely go for 25s rather than 23s.

 

[asterix]

My bike had 23s and I have replaced them with 28s. I'll be using it for a sportive event in May that will be 100 miles and I want a bit more comfort. There is a time cut-off but I don't think the tyres are going make any difference to whether I make it or not. When I used the 23s on the Spring into the Dales ride the road surfaces gave me a lot of grief.. The hills I could manage.

I really think the only difference is slight extra weight and wind resistance.

 

[frank9755]

According to lab tests if tyres are pumped up, the wider tyres will actually roll better but try telling that to Wiggins, Cavendish et al. I think they are on 23mm.

On a persosal note my Kinesis used to have a 23 front/ 25 rear combo; when the 25 wore out the 23 was moved to the rear and a new 23 went on the front I've noticed little if any difference. I also changed the 28's for 25's on the Sirrus I found that made a more noticeable difference without too harsh a ride but how much of it was to do with me getting fitter and other mods (new wheels, drop bars & carbon seatpost) I couldn't quantify. Probably others will have other opinions but I think 25mm are the best compromise for comfort/speed.

Yes, but the point is that you can pump 23s up to a higher pressure. It's the pressure, not the width which makes them roll faster. The giveaway line in the article - which they don't bother to explain - is 'all other things being equal' - but they're not equal because 23s will be at higher pressure!

The OP wants the fastest tyres for racing. If he wasn't racing it wouldn't be worth bothering to change. Like you I use 25s on my commuting bike, for audax, sportives, etc, but on my time trial bike, where I will sacrifice comfort for speed, I have some very fast compound 23s at high pressure. My touring bike has 32s and my pub bike has 37s.

Sheldon's logic was that if you are going to have different sized tyres, you get optimal results from having the fat one with the lower pressure on the front, not on the back: lower rolling resistance from the one that bears most weight and a softer ride from the one under your handlebars.

 

[HLaB]

Yes, but the point is that you can pump 23s up to a higher pressure. It's the pressure, not the width which makes them roll faster. The giveaway line in the article - which they don't bother to explain - is 'all other things being equal' - but they're not equal because 23s will be at higher pressure!

The OP wants the fastest tyres for racing. If he wasn't racing it wouldn't be worth bothering to change. Like you I use 25s on my commuting bike, for audax, sportives, etc, but on my time trial bike, where I will sacrifice comfort for speed, I have some very fast compound 23s at high pressure. My touring bike has 32s and my pub bike has 37s.

Sheldon's logic was that if you are going to have different sized tyres, you get optimal results from having the fat one with the lower pressure on the front, not on the back: lower rolling resistance from the one that bears most weight and a softer ride from the one under your handlebars.

Aggreed, I don't give too much weight behind lab tests

Racing, That's kinda what I was hinting at the pro's use 23mm, it kind of throws those lab tests out the window, I recckon they know what they are doing.

I cant remember the full in and outs of Sheldon's article but iirc it was quite balanced between the pro and cons of each method on tyre sizing (I think the pro's of the wider tyre on the back were more important to me and I doubt mere mortals would perceive the difference; I certainly can't). Just to muddy the water conti brought out their force/attack system (24mm rear/ 22mm front)

 

[John the Monkey]

I went from 32c to 42c on the Long Haul Trucker (and 90psi to 60psi) and didn't see my commuting averages change at all.

 

[PK99]

Aggreed, I don't give too much weight behind lab tests

Racing, That's kinda what I was hinting at the pro's use 23mm, it kind of throws those lab tests out the window, I recckon they know what they are doing.

there are other issues at play in addition to rolling resistance: rotating mass - the lighter the better - and aerodynamic drag - no point i having aero wheels if the tyre itself creates drag

At the same pressure a wider tyre has lower rolling resistance, but this is outweighed by the greater rotating mass and, most significantly, greater drag