I'm setting up the computer and looking at the manual's chart for a 700x25, the number is 2096. However, the measured circumference of the tire is 2135 which happens to be the manual's number for a 28 tire.

So, slightly confused, I set the computer for the actual circumference. After a couple rides I've concluded 2096 must be the right number even though its not the actual circ of the tire. Saturday my computer read more than 1 mile more than our ride leader in a 50 mile ride. Sunday, I noticed my computer did not mtach the cue sheet and by the end of a 56 mile ride, was, again, over a mile more.

I've reset the computer back to what the manual says (2096).

Has anyone else found this to be true and if so, I wonder why the tire size in the manual does not match the actual circ of the tire?

BTW, this is the second computer I've found this to be true - both different brands.

I'm a bit anal maybe but I want my computer to be accurate.