Originally Posted by Stitch
No matter where you put the magnet, it will pass by the sensor once per revolution. That said, at higher speeds, the magnet will be passing the sensor faster, so you may want to position it closer to the hub, because if it's out by the rim it may pass the sensor too fast for it to be registered.
Then again I've seen people using cyclocomputers near the middle of the wheel on their motorcycles with no problems, so the advantages in placement are possibly academic.
I've hit just shy of 50mph on my road bike and I have the magnet about 2" in from the edge of the rim on my road bikes. I've never had a problem with it picking up the magnet as it sweeps past.
BTW-I actually have a speedo bathing suit. I wear it under my wetsuit when surfing so that I don't have to worry about my junk popping out when I strip off my wetsuit at the car.
