Originally Posted by
KC8QVO
What I don't like about the "measuring the circumference of the wheel" method is this does not take in to account the compression of the tire when under load.
That is why I am trying to get an accurate course distance measurement. Then I can tune the calibration factor on the computer per bike so that the reading is repetitive and correlates to the measured course.
You may be a bit OCD, but not unreasonably so. My rollout tests correlate pretty well with the computers' manufacturing instruction sheets. When I get on the bike and go for a ride, though, I find that going for the next smaller size tire on the sheet gives me a better match to the ride distance. E.g., a 700Cx32 tire matches mile marker and GPS ride distance better with a x28 calibration factor, or use the x25 calibration for a x28 tire.
Of course that's going to vary with rider weight and tire pressure. I suspect it will take some trial and error to find what works best for you.