Trevor98

If the magnet is close to the rim it is traveling slower than if the same magnet is mounted closer to the hub and the faster speed may (slight chance) confuse the sensor at extremely high road speeds, however, placing the weight closer to the rim would theoretically negatively effect acceleration. These two issues are pretty irrelevant to reality. The speeds at which the wheel would have to spin in order to confuse the sensor would have to be unreal and the slight weight of magnet near the hub is almost too little to compute.

Basically, everything I have read on the subject indicates that function is not really impacted by location on the spoke so go for ascetics.

Ironic Mullet

You keep using that word. I do not think it means what you think it means.

DrPete 

Yeah, I don't think an ascetic would even have a bike computer, much less a fancy bike.

x43x

Here's another question for the nit-pickers; What way do you mount your sensor? On the front of the fork, or behind the fork? Does either effect aerodynamics? I recently moved mine from the middle and rear of the fork, to the top and front of the fork. Looks was the only reason. It looks better to me just under the brake caliper.

DrPete 

I was told that my sensor placement was un-aero. I'll use all that extra resistance (must be AT LEAST 0.001W) to train harder.

daytonian

Behind

DrPete 

^^^ Ooooh, daytonian, she's purdy. Very nice...

daytonian

Thanks. She's filthy after yesterdays slogfest in the sleet which you got today.....but I like em filthy

Trevor98

stupid spell check.

DrPete 

Yeah, it took about 2 hours to clean mine off today. I still love that you can clean CF with Pledge. Lemony fresh!

goaliedad30

Definite YouTube opportunity here ...

Brueg

I've used my GPS with my three different cars and all of the speedos indicate about two MPH fast. Both my road bikes have been correct. One has a Cateye and the other a Serfas.

Endox

If you're really fussy about calibration like me then measure the circumference by marking a position on the tire and moving it forward one revolution while sitting on the bike and on a road surface. You should easily be able to get a value within 1cm which would make it accurate to about +/- 0.5%.

Al1943

All of my sensors go on the left rear chainstay.

noisebeam

Exactly my experience too for moderate priced aluminum rims (i.e open pro). If I add a typical magnet on the valve side (with tube installed) I still find it to be lighter - that is the added magnet weight it still not enough to make up for the seam weight. Obviously this will vary by wheel design.

I like the idea of putting the magnet closer to hub, so the time it takes the magnet to pass the sensor is slower, possibly leading to less chance of miscount at top speeds.
But sometime short wire length has had me put magnet closer to rim and I've never noticed a problem.

As to calibration, wheel rollout is best as explained by Sheldon. I put a dab of white out on tire

https://sheldonbrown.com/cyclecomputers/index.html

Al

orcanova

speaking of computer mounting...there was a pic somewhere in this forum of a Polar HRM strapped to the bars in a rather ingenious way that did not involve using the mount. It was pretty cool and remember it got a few oohhs and ahhhs from Polar users.

Anyone have that pic...?

edit: found it...




https://bikeforums.net/showthread.php...nt#post3111399

garysol1 

Just slide the loop up to the top of the strap. Run the other strap through the loop so that both straps pass through the loop. Spread the straps apart below where they come through the loop and just it on the bars as you would around your wrist.

edit: you found the pic..

orcanova

^tnx!

staehpj1

Cars typically have an error of 1-2%. You can do that well by entering the number from the chart for your tire size. If you want to verify there is a lot of info on this at https://www.sheldonbrown.com/cyclecom...libration.html

xlrogue

Once you've got your sensor in a good position on the fork (or the rear stay, as the case may be), you might want to secure it with a dab of RTV silicone glue (the kind that smells like vinegar when its wet), which will keep the sensor from moving but will peel off pretty easily without damaging the sensor or bike finish if you need to remove it.