Another newbie question....
I bought a cyclocomputer today to keep track of my distance and time on my new bike.
The instructions explain how to change the tire size in the odometer function. The default setting on the computer was 820. I have 700x40c tires on my bike. The side of the tire says "42 - 622 (700 x 40c)". How does all that correlate with the default setting on the computer? I can raise or lower that number..... but to what?