I have three bikes, with three different computers. Setting the wheel size is no problem. However, none of the instructions state where to put the magnet on the spokes - how far up from the center. Clearly the position of the magnet is critical for an accurate reading of speed and distance, so you would think that there is a formula somewhere, at the very minimum in the instructions.

Anyone know the answer?

Also, does anyone know if tire size affects the reading? for example, 19 vs 21?