Originally Posted by
Steve B.
I usually do a roll out. I lineup the valve dead up/down, mark the floor with a piece of chalk, roll the bike so the wheel makes a complete revolution, mark the floor where the valve is, measure and enter that info. It's not 100%, some folks state you need weight on the tire to emulate a rider on the bike compressing the tire, but jeez, it's close enough.
I like to use a tape measure for that -- start with the valve at the end, roll until the valve is down again, read the tape.
