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Cadence sensor too far away? Fix?

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Cadence sensor too far away? Fix?

Old 07-30-09, 09:05 PM
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sherpa41
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Cadence sensor too far away? Fix?

The chainstays on my 2007 Specialized Roubaix are curved and flare outward near the rear axle. Since they're not straight, there is too much clearance between my crank and the chainstay to get the cadence sensor to pick up the magnet signal. Anyone have any ideas for fixes? See the 2 pictures (sorry about the crummy quality). Right now there's about an inch between the sensor and magnet, 1.5" between the chainstay and crank right there.
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Old 07-30-09, 09:15 PM
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There was a thread about a lost magnet and getting a cheap replacement. This brought up Neodymium-Iron-Boron, which has the highest magnetic flux of any consumer-grade material. Google it.

Also, a larger magnet, or two magnets stacked will generate stronger flux, and the latter will also put the stacked magnet closer to the sensor. Glue the magnets together with superglue, Goop (for solvent-reversible mod) Gorilla glue or epoxy.
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Old 07-30-09, 09:46 PM
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I have a pedal with chromoly bolts. Asked my son for 2 magnetic marbles from his magnetic erector set and stuck them inside the crank pedal thread. Those are strong magnets, strong enough to wipe out a 2.5 usb external drive when it got too near
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Old 07-30-09, 10:08 PM
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Cateye?



My Sigma came with a spacer for the magnet. The cateye did not, but a spacer of some sort is obviously neccessary maybe on the sensor. I had some double sided rubber/foam tape from a vintage car restoration that was about 1/8" thick. A couple of strips of something like that held in place by the zap straps might do the trick.



It looked like this:


Google double sided foam tape if you are interested.
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Old 07-30-09, 10:38 PM
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Originally Posted by Eclectus View Post
Also, a larger magnet, or two magnets stacked will generate stronger flux, and the latter will also put the stacked magnet closer to the sensor. Glue the magnets together with superglue, Goop (for solvent-reversible mod) Gorilla glue or epoxy.
I needed two magnets. Went to the hardware store. They stuck right onto the pedal axle. The held together with magnetism.
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Old 07-31-09, 01:06 AM
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How amusing, I too have a Roubaix and that Cateye. I cut a section of a busted tube, folded it over until I got the right thickness, then zip-tied it under the sensor on the chainstay.

It's a complete eyesore, but it works.
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Old 07-31-09, 02:13 AM
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Use something to pad between the crank and the magnet, and then strap it down? Alternatively, as other suggested, use a more powerful magnet.
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Old 07-31-09, 02:41 AM
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Find one of those powerful tiny magnets.
The bike computer ones are usually pretty weak.
Test, then epoxy this to the crank arm.
Voila. Lighter, more aero, better aesthetics (one fewer strap required).
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Old 07-31-09, 03:08 AM
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had same problem, simply put 2 small piecies of rubber under the sensor.
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Old 07-31-09, 06:36 AM
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Be sure to clean your bike before you try to get your cadence working. Geesh!
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Old 07-31-09, 06:39 AM
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Pad the sensor. Your lbs probably has a stash of rubber spacers from lights and other handlebar gizmos. Also getting neodymium magnets will help too
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Old 07-31-09, 06:45 AM
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Originally Posted by calyth View Post
Use something to pad between the crank and the magnet, and then strap it down?
+1

That's what I did when I had a Garmin with a cadence sensor.
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Old 07-31-09, 08:37 AM
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Thanks, all. It's a CatEye Strada computer.

It actually did come with a (small) pad to put behind the sensor but it's just not big enough. My pedal spindles are stainless (which isn't magnetic, right?) but I'll look into mounting a stronger magnet or shimming the sensor closer.

Be sure to clean your bike before you try to get your cadence working. Geesh!
I know! I meant to clean it after my last ride... but then I didn't. I like a clean bike too, just have to get off the old posterior.
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Old 07-31-09, 10:37 AM
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Originally Posted by sherpa41 View Post
Thanks, all. It's a CatEye Strada computer.

It actually did come with a (small) pad to put behind the sensor but it's just not big enough. My pedal spindles are stainless (which isn't magnetic, right?) but I'll look into mounting a stronger magnet or shimming the sensor closer..
The pedal bolts usually are steel, and will hold the magnet in place (or even two magnets) with no additional glue or tape required.
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Old 07-31-09, 11:09 AM
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Just so I am clear, you guys are attaching the neo magnets on your pedal bolts, not behind it (further from the end) like they would be traditionally with double sided tape and the ziptie, right? Magnets don't stick to my crankarms but they do to the bolt.
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Old 07-31-09, 12:34 PM
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pedal axles are made from either stainless steel, cromoly or titanium, since they are subjected to such loads that other materials will simply snap.

all your magnets will stick to stainless and cromoly.
if the magnets are really strong, like neodymium that is commonly available, they will be extremely hard to remove once you attach it to the pedal spindle.

just to tell you how strong they are, a 1x0.5in square of this magnet can lift a good 10kg. They're pretty good at crushing fingers too.
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