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Discussion Starter · #1 ·
Hi guys. I recently went tubeless using a pair of Crank Brothers Cobalt 3's. I know those take a bit of flack on the forums but it seemed like it would be less trial-and-error than ghetto tubeless and for 30% off through CB's wheel upgrade program, I figured why not try them. So far so good.

But I'm curious if anyone has any suggestions for mounting a magnet to my front wheel, for the sensor on my bike computer. The closer to the hub, the smaller the distance between the fork and the spokes, but the magnet also needs to be far enough out that it doesn't hit the brake caliper. Unfortunately, at the spot, the distance between the sensor and the magnet would be just a little too far for the sensor to register the magnet's passes. That position also puts the magnet on the inner half of the spoke. I'm not sure if it will fit that thicker part. (See the pic below.)

Does anyone have any slick suggestions for mounting a magnet a little further out and to a fatter-than-normal spoke? Or does everyone just use Garmins now? :)

- Brandon

photo.jpg
 

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mount it on the other side, and by other side i mean the other fork leg, that way you dont have to deal with the brake caliper and you can get it closer.
 

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Discussion Starter · #4 ·
Yeah, epoxy might work. Might also make changing a spoke a pain if I ever need to. I was hoping maybe there would be some sort of MacGyver trick for clamping a magnet onto a spoke (at a distance) using a zip tie and a paper clip. :)

I was also hoping to avoid running the wire down the other side of the fork because wrapping it down the brake side helps take up so much of the extra wire. But it's definitely an option. Maybe my best one (although that would still put me on the fat half of the spoke.)
 

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I mount a small rare earth magnet on the rotor below the caliper line and then mount the sensor inline with this. I doesn't interfere with anything and has worked well on my lefty for around 1,000 miles. You an get a pack of magnets for around $2.

Tim
 

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Discussion Starter · #6 ·
Now we're talking! If you look at the picture on my original post, there's actually a rare earth magnet stuck to one of the spokes. :) How do you secure it to the rotor? Epoxy or something else? Or is it generally strong enough to hang on? I'd hate to fling it into harms way.
 

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Discussion Starter · #8 ·
Hmm. Mine might be a little weak for that. They stick but I'm not sure how securely. I'll have to see what I can find.
 

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As I said, mine's never come off after 1,000 miles and it hasn't moved going by the fact that the computer hasn't missed a beat.

Are you trying the original magnet or a rare earth one? The latter are much smaller too.

Tim
 

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Discussion Starter · #10 ·
I have a pack of rare earth magnets that I bought a while ago for something else but they are kind of small and therefore not especially strong. They are 10mm in diameter and maybe 1.0-1.5mm thick. I'm just worried about them sliding to the outside of the rotor because of jarring or centrifugal force.

About how big is the one you're using?
 

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Discussion Starter · #12 ·
I tried. It shifted... although inward, toward the hub instead of out toward the rim. Oh well. Looks like I need a stronger one. Or some glue. Or both.
 

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With respect to an alternative to epoxy:
InstaMorph - Moldable Plastic
Instamorph is a thermoplastic which becomes moldable by heating in boiling in water. As it cools it solidifies into solid plastic-- perfect for this application. I use it for prototyping parts routinely. It is also perfect for making custom casts for broken fingers. If you want to change its color to black, add some food coloring when hot.

It shrinks around 5% once cooled, causing it to tighten up on parts it envelops.
 

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Discussion Starter · #15 ·
By the way, I ended up buying a cheap mouse pad and cutting a small square out to put under the sensor, pushing it closer to the magnet on the spoke. It worked great.
 
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