Speed sensor - placement matters??
 

Got a basic bike computer and took it out on its first run today

Something dawned on me though. Even though i put the wheel size in, wouldnt the sensor placement matter more? For example, for someone with disk brakes, you could put the sensor farther to the edge of the wheel. I have rim brakes,and had to mount the sensor quite a bit lower. Wouldnt my sensor come around more frequently than the one with a disk brakes, thereby giving me a falsely elevated speed and distance reading? Thats even eith wheels that are exactly the same size?

Err, in a word, no. The magnet passes the sensor once every time the wheel turns around.


It may be advantageous to put the magnet and sensor fairly close to the hub. Close to the hub the spokes are nearer the frame, so the magnetic field is stronger at the sensor. Also, when the magnet is nearer the hub, the sensor has longer to respond before the magnet leaves the sweet spot.

Further out towards the rim, the switch "on" state is shorter duration, I think, which would have less noise in the measurement. But it doesn't really matter.

OK, you are right, lol. Stupid me. The magnet still passes once for every one revolution of the wheel, so it is all about tire circumference. I guess I can't math and ride a bike at the same time.

I wonder if I can delete this embarrassing thread?

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