Where ever you can get it positioned to pick up the revolutions and stay securely in place. Other than that, no rules, which is why the instructions don't have any.
Originally Posted by
merlinextraligh
Put it as far out as possible. The magnet will be moving much faster, amd your speeds will improve.
No, put it as close to the hub possible. It reduces rotational weight.
Originally Posted by
ScrubJ
I usually mount the magnet opposite of the valve stem (balance)
For most rims, the seam is heavier than the stem, so if you're trying to balance the weight (not that it helps), you want it on a spoke that leads to the stem.