Put one of these in your saddle bag for your next ride...


Seriously though rollout methods will work fine. Odometers in cars are really just suggestions of how far a car went. Tell that to the judge the next time you get a speeding ticket. Tell him your spedometer was not calibrated to the specific rollout of the tires on your car so you had no way of knowing you were going 20mph over the speed limit....they like that kind of stuff...