Quote Originally Posted by michelem View Post
Not that I have any clue what this means, but this is the info I got off of specialized.com:

The Roubaix Pro clincher is the easiest, fastest way to turn long & fast rides into long, fast, comfortable rides. In a unique construction design that merges a faster 23c wide tread with a more comfortable large-volume 25c casing, this tire offers a fast rolling, great handling tire which damps road vibration and increases riding comfort without sacrifice.


700x25c casing matched with a 23c wide dual compound 70/60 tread
DRT design for low rolling resistance and great cornering
120 TPI casing

Anyone?
well .............. hmmmmmmmm

sounds like the 23c wide tread is what touches ground?; large-volume 25c casing is the inside volume of tire -- meaning it has the volume of a 25, but instead of touching ground like a 25 (more tire rolling on ground), you have a 23 coverage (less tire rolling on ground -- think racing and less rolling resistance) ... so, you get the comfort of a wider tire and the rolling resistance of a smaller tire. Now, what that means for a cycling computer -- heck darn, I don't know!

PURE GUESS: I would go with 23c because that is what is hitting ground.

since it is a new bike, would the bike shop know?!