Originally Posted by
hy_tek
I do have one more favor to ask however. When I looked at the wheel circumference chart they gave me, my particular tire is not listed. I do not have any metric measuring devices to actually measure for myself. The closest I can figure is 2150mm.
My tire is a 700 x 38C.
If you want to be really exact about it, you should measure. Often. But if you cannot measure it, I think you're close enough. Sigma's manual for example suggests 2105 for 700x35C and 2224 for 700x40C. From that, I would enter 2175mm or so, which is a whopping 1,1% above your figure. It only takes a 7,5mm change in tyre diameter to cause about the same error.
--J