One quirk from using the French name 700C is tha people thing C is a unit of measurement. People say they want a 29C tire when the mean 28mm. I've also heard people say they have 700CC tires, because CC is a unit of measurement, i.e. cubic centimeters. But that's not it, either. 700C refers to a diameter of 622mm, as measured at the bead. 700x28C is really 700C x 28mm.

Confused yet?