25 are faster than 23s - discuss

gaddster

gp4000 s 25's

El Selb

that isnt one of the options!

meanredspider

I'm in the middle of an experiment on this. I used to run 23c Gators but, after reading the article on here, I thought I'd try 25c Gators. My first data point is that, after 1000 miles or so, I haven't managed to match my highest speed down a hill on my commute - in fact, it takes everything I have to get close to it.

My next data point (and don't all shout at once...) is that I've now fitted 23c GP4000Ss and this week I've blitzed my fastest times (ca 2-3% faster). And, yes, yes, I know they are a "faster" tyre and there's a slight confounding factor that, riding with Lance (and 400 other people) at the weekend, my confidence in my ability is boosted (nothing to do with LA and more to do with the 400 other people). After I've had a chance to get enough miles in on these tyres, I'll switch to the 23c Gators to try to isolate the tyres construction from the tyre size and see what difference they make.

I'm finding it hard to see where aero has an influence in all of this. The difference in "bluff area" (the frontal silhouette) between bikes fitted with 25c & 23c is about 4cm2. That's less than my water bottle holder (without the bottle in it). I can't see the Cd (shape factor) being influenced much by the tyre width.

What I'm expecting to find is that there's not much difference between tyre widths (25c & 23c) and far more difference between tyre constructions.

Thebigbee

I am not at uni any more so don't need or want to "discuss" anything ever again.

Maybe when we have a rare all night session but in the real world...

Thanks anyway but ZZZZZzzzzzzz

holker

Omar Little wrote:

I dont really notice much difference between 23 and 25 in terms of comfort and relative speed. With 25 i have to loosen my brakes (open them more than what the lever thingy can do) when changing a wheel so that can be a pain in the ars* trying to get them aligned just as i like them again

I just let some air out of the trye. Seems to do the trick, and is easier than fiddling with the brakes

holker

Omar Little wrote:

I dont really notice much difference between 23 and 25 in terms of comfort and relative speed. With 25 i have to loosen my brakes (open them more than what the lever thingy can do) when changing a wheel so that can be a pain in the ars* trying to get them aligned just as i like them again

I just let some air out of the trye. Seems to do the trick, and is easier than fiddling with the brakes

springtide9

Pretty sure from what I've read, rolling resistance depends on tire width, rolling speed and surface texture (rough/smooth). I guess it also depends on the tire compound to some extent.

Only used two sizes so far, 25mm (Conti GP) and 24mm R / 23mm F (Conti GP Attack/Force)

I can tell already the 24/23 run faster on smooth ground but the 25mm seem to do better when it gets a bit rougher.

As I have no idea on how to rate roads in terms of their rough/smooth rating and/or not every ride has the same tarmac... I figure the only real way to figure out what's 'generally' best is trial and error - or asking 'local' advice (from their experience)

balthazar

meanredspider wrote:

What I'm expecting to find is that there's not much difference between tyre widths (25c & 23c) and far more difference between tyre constructions.

I agree with this —and I think that's the primary conclusion from the graphs I linked to.

toontra

springtide9 wrote:

I can tell already the 24/23 run faster on smooth ground but the 25mm seem to do better when it gets a bit rougher.

In other words use 25s in the UK and 23s in the rest of Europe!