Pretty simple question I hope. I picked up a Bontrager Trip 3 because I saw it recommended several times for rear mounting (this is on a bike that will sit on a trainer). However, I am finding that there is nowhere on the rear portion of the body that puts the speedometer sensor close enough to the spokes of my wheel for it to sense the magnet as it travels. The only place I've found that might work is on the plastic sheath around the brake line near the rear disk brake. It looks like it requires about 1-3mm distance to be able to pick up the magnet - there's almost nowhere on my bike's body that comes that close to the spokes. The brake line sheath isn't very stable (it's just hard plastic) but it seems to work.

The only other option would be about 1" of shimming near where I have the cadence sensor.

The seatstays and chainstays for the bike are extremely wide because of disk brakes.

  • You should be able to get easily more than 1-3 mm of range between the pickup and the magnet.
    – Batman
    Commented Dec 2, 2014 at 2:56
  • Can you? Yes. Is it a good idea? Not IMHO :-)
    – andy256
    Commented Dec 2, 2014 at 2:57
  • @Batman according to bontrager/Trek, the required distance for both the cadence magnet and speedometer magnet and their respective sensors is 1-3mm. After testing by hand, that seems to be 100% true. Given the wide chainstays and seatstays, theres pretty much nowhere where I can get that close.
    – Matthew
    Commented Dec 2, 2014 at 2:57
  • 2
    If the bike is on a trainer and will not bounce around you could maybe hack in an extension like a block of wood and a zip tie?
    – paparazzo
    Commented Dec 2, 2014 at 3:12
  • 1
    What else might work is like a light or lock attachment. I save all my old attachments and shims.
    – paparazzo
    Commented Dec 2, 2014 at 4:11

1 Answer 1


I have had a similar problem and solved it by using a small piece of foam pipe insulation. I see no reason why a piece of sponge or similar material wouldn't work. I used two zip ties to hold the spacer in place, then positioned the sensor pick-up.

  • I can confirm that this does work. Pipe insulation foam seems to work best as it is a little stiffer.
    – Rider_X
    Commented Dec 2, 2014 at 16:40

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