Originally Posted by Trail Blaster
I just need to calibrate the cyclocomputer itself for my tire size. My tire size is 26 x 1.85, which isn't listed in the user manual so I have to guess the right number to use.
Do a rollout test and enter the actual number if you can - measure by rolling the bike while you're sitting on it for one wheel revolution.
Using the valve stem as a reference point is probably easiest - start with the valve over a line on the floor, and stop measuring when the valve is back at that same point one revolution later. Other option is to put a small dab of paint on the tire and measure between the marks it makes on the road.