Quote Originally Posted by SadieKate View Post
If you want it to be that precise, how about using the rollout method in the instructions so you only have to do it once?
The rollout method is good to get you in the general ballpark. (Be sure you are sitting ON your bike when you measure the rollout, and it helps to have a helper.) But the rollout method is just not the same as when you are going your normal speed and longer distances. Road surface contact and tire compression will be different at normal speed, and give different results. I also found the little chart for typical tire circumferences that came with the computer to be pretty inaccurate when I actually measured it against my two different tire sizes.

I used the rollout method to get within the general range. Then I drove our two different cars a certain route that was exactly 10 miles. Both cars read the same. Then I rode my bike a few times that same exact route and adjusted my tire rotation setting each time until it matched the 10 miles. You can't get nearly as accurate by rolling at almost a standstill for 12 yards.