Originally Posted by
unterhausen
A wheel-on trainer knows how far you went because it can count the revolutions of the pick up wheel and multiply by the circumference of the pick up wheel. It has nothing to do with the wheel size of your bike.
1) And how does it know the circumference ? I assume it takes the diameter of a standard wheel -- 26" -- and multiplies it by 3.14. That's how you get the circumference of any circle.
2) My confusion is; if I multiply the circumference by the revolutions per minute (my pedaling cadence) and multiply that by the the number of minutes it took me to finish the course, I should get the total distance of the course. But when I do that calculation -- circumference x rpm x minutes to finish the course -- I get ~ 5.84 km. But the length of the course, according to the software is 16.1 km