Running different width road tires?

[danfoz]

Anybody have any thoughts/experience running a 25c rear and a 23c front?

I've personally always run the same tire widths and also heard some advocate against the practice of mixing, but looking at the Conti Attack/Force combo at 24 rear and 22 front, the cushier ride for the rear combined with the slightly more aero, slightly less deforming tire for the front to take the brunt of cornering/braking vectors seems like it makes sense, at least on paper. With the exception of a few vintage applications, motorcycles run mismatched sizes pretty much across the board

Asking as am thinking of trying this out with a pair of mis-matched 4000s, which weren't specifically designed with the mis-match in mind.

 

[maydog]

I ride a 23f / 25r combination all the time. I cant tell any difference from riding 23f/23r, but I put the same tire pressure front and rear. I use a larger rear primarily due to my clydesdale status.

 

[danfoz]

Thanks for the feedback Maydog - I have 2 diff sizes in pretty good shape laying around as I used them on the front and swapped out before rotating, I'll probably just give them a go.

 

[Dr Lodge]

Originally Posted by maydog .

I ride a 23f / 25r combination all the time.

That's probably a really good idea, there's more load on the rear so makes sense to have a slightly large tyre.

 

[alienator]

The braking argument doesn't work since the contact patch--all else being equal--will be the same for two different sized tires given the same inflation pressure. Of course, all else is rarely equal. Using Sheldon Brown's figures for tire circumference (2097mm for a 23, 2105 for a 25), a first order approximation yields 9.1% more drag for the 25mm over the 23mm. Again, that's just a first order approximation. The 25 will have lower rolling resistance at a given inflation pressure since it's contact patch will deform the tread less. Given all that, the real differences are likely to be very small. What to do........go with what feels best and best polishes your chi. It's s.o.p. in racing to make changes with minuscule benefits in the off chance those minuscule benefits make the difference on some race day. Also, remember that 25 on the front will provide less impulse from road deformities than the 23 (yes, once again, at a given pressure), which will minimize fatigue. Everything should now be clear as mud.

 

[danfoz]

Originally Posted by alienator .

The braking argument doesn't work since the contact patch--all else being equal--will be the same for two different sized tires given the same inflation pressure. Of course, all else is rarely equal. Using Sheldon Brown's figures for tire circumference (2097mm for a 23, 2105 for a 25), a first order approximation yields 9.1% more drag for the 25mm over the 23mm. Again, that's just a first order approximation. The 25 will have lower rolling resistance at a given inflation pressure since it's contact patch will deform the tread less. Given all that, the real differences are likely to be very small. What to do........go with what feels best and best polishes your chi. It's s.o.p. in racing to make changes with minuscule benefits in the off chance those minuscule benefits make the difference on some race day.
Also, remember that 25 on the front will provide less impulse from road deformities than the 23 (yes, once again, at a given pressure), which will minimize fatigue.
Everything should now be clear as mud.

Huh?

But I concur, real world differences are likely to be small with those in comfort likely being realized more readily than those of performance. Since I have noticed that different tires can feel palpably different, with some lending more confidence than others at the edge of traction, just wanted to make sure I'm not diminishing handling in any way even if it is a miniscule amount.

 

[alienator]

How timely: http://velonews.competitor.com/2012/05/news/giro-tech-rise-of-the-25c-tire_218011