Road Cycling - Wheel magnet

I've been wondering what are the correct place to put a wheel magnet in terms of inches from the rim, I've been thinking you get different reading when its nearer to the rim you tend to get a slower reading or when you place it lower at the spoke nearer to the hub you get a faster reading. So is there an international standard to these?

Read the instructions.

well if its written in the instruction I wouldn't have posted the ques here.

it really shouldnt matter as far as the readings go. no matter where you put the magnet on the spoke (between hub and rim) it makes the same amount of RPMs. the tangential welocity is different, because the circumference of the round trip it makes changes depending on its location, but the magent and the computer calculate the speed depending on how often the magnet passes the sensor, and not on how fast it is moving as it passes.

so after all that mess ;)

if its for a wireless cyclocomputer id recomendputting the magnet/sensor as far up the fork (close to the computer) as possible w/o interfering with the brakes. if its wired, then just put it where you like it best, as long as you have enough wire to get there.

I like to put mine opposite the valve stem for a more balanced wheel. But that might just be my anal side appearing.
Something else i was thinking and someone here may know more. If you put the magnet further out on the wheel will that increase the rotational weight of the wheel as compared to closer to the hub?

I have a few computers so here is my take... It is usually better to put the magnet/sensor as close to the hub as is practicle. As was indicated by another poster, as you move closer out to the rim the magnet will be whizzing by the sensor at a faster rate. In my experience you have a greater chance of the sensor missing one of the pulses. Also, the chances of a weight induced vibration increase as the mass moves farther from the center of rotation ie.. the hub.

skareb.......it makes absolutely no difference in reading where the magnet is placed. One revolution of the wheel will give you one magnetic pulse no matter where the magnet is placed. Comprende?

It doesn't matter.
When I got my present cycolcomputer I mounted the magnet about 2" from the rim.
After about a year I thought I'd try it mounted about 2" from the hub. Don't ask why.
Same reading in both loactions.

It dosen't matter. The speedometer is simply counting pulses. Each end of that spoke that you attach it to passes the sensor the same number of times per minute.

I do put them opposite from the valve stem.

I guess if you got super super critical, closer to the hub would be better from a rotational weight standpoint. I don't think you could ever tell the difference.

I think it is best to pick the best location for the sensor and let that determin the location.

if you use two magnets, you'll go twice as fast :D

if you use two magnets, you'll go twice as fast :D......assuming you put the magnets opposite from one another. You can go ten times as fast if you mount two magnets just one spoke apart.... :eek:

I put one on every spoke and now my bike is super fast. I can prove it... Just look at the readings on the computer

Ok I've email cateye and this is thier answer

Dear Michael,

Thanks for your mail. Any point on the wheel will make one revolution in
the same amount of time. When the wheel makes one revolution, it always
travels the same distance, based on the wheel circumference. The computer
counts how many times the wheel turns, and multiplies this times the
distance (wheel circumference) to get the speed. In short, you can place
the magnet at any point on the spoke, as long as it is properly aligned
with the sensor.
Please let us know if you have any other questions.

Best regards,

David Alvarez
CatEye Co.

I like to put mine opposite the valve stem for a more balanced wheel. But that might just be my anal side appearing.


No your not being anal, this is something that I've done for years and when I got my last computer I absentmindedly placed the magnet about 1 spoke away from the stem and when upon riding it got a vibration. Once I came to my senses and relocated the magnet opposite of the stem the vibration went away. So that was an excellent point you brought up.