Originally Posted by scotto-
Yes, or mark your tire with chalk and chalk the pavement at the same point and with the help of a friend have them steady you and roll forward until one revoluton and mark the pavement then measure the distance between the two marks. The rolling circumferance in inches or millimeter and input for the calibration. Same, same and same. All the methods work.
This is the best and most accurate way. Oil will spread, not to mention what it will do to your tires, string can be stretched.