Thanks! I will def check my clearances before buying anything, as well as measure my current tires for comparison.Bigger Gear wrote: ↑Thu Nov 29, 2018 7:29 pmOn a 17mm internal rim, the Conti 23C will be 25.5ish. The 25C will be 27.5ish and the 28C will be 30.5ish. Another thing is that the Conti tires are tall for stated size. I could not run a GP4000Sii in a 25C on a rim 17mm or larger on my Colnago C60 because it would be too close to the fork crown. But, I could use a Vittoria Corsa G+ in 25mm width on a 20.5mm inner no problem. So for the OP, make sure you can get a 25C GP4000Sii to fit before buying them.
And Hexsense is on to something important, having the inner width significantly more narrow than the tire width creates a very different riding tire. I've played around putting a 28C Conti on a 15mm innner width rim, and on a 20.5mm inner width rim with all other variables kept the same. The narrow rim gives the tire much more of a lightbulb shape and the feeling under hard cornering is much more vague. And climbing steep grades out of the saddle, the front wheel always feels more flexy. This is the effect of the very round sidewall on the 15mm rim vs a much more vertical sidewall on the 20.5mm rim.
For the wheels I have that are 17C I use either 23C Conti or 25C Vittoria.
I should add that it's hilly here, my last ride was about 3400ft of climbing. So I want it to climb and descend well. So maybe the 23c Conti would be better for my purposes. What kind of pressure do you run with the 23c Conti?