Cateye Strada Smart CC-RD500B Online Manual page 110

To determine tire circumference (L) with more accuracy, measure the tire using the method
below.
* When using Cateye Cycling™, you can simply select the size indicated on the tire.
Measure actual tire circumference (L)
With tire air pressure adjusted appropriately, apply a load to the bicycle.
Using the valve, etc., as a marker, rotate the tire once and measure the distance traveled
along the ground.
Determining tire circumference
When using front
wheel for speed
measurement
When using rear
wheel for speed
measurement