Re: How to Calibrate your Speedo Correctly
Good suggestions. Personally I just lay a tape measure on the ground and line up the stem on the front tire so that it is perpendicular to the ground and at the beginning of the tape measure. Then I roll out one revolution and get the reading right off the tape measure.
But the idea is to enter the actual tire circumference in millimeters into your cycle computer. Not all tires are created equal so using a general "guide" isn't always accurate.
I suspect some of these speed claims are made with mechanical speedo's which aren't even close to accurate.