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With chainstays set so steeply outward to accommodate wider tyres, the gap between the cranks and the chainstays is truly minimal. How do you secure your single-piece (accelerometer-based) cadence sensor and avoid losing it if a twig or similar is squeezed? It normally attaches with just a rubberband, and the attachment cannot be permanent since the battery inside needs to be changed (yearly).

One idea is to do what some people do with their luggage at airports: wrap with saran wrap. But that's of course hideous.

A picture of your working solution is worth many words.

Update

The only place where I can fit this (perhaps fatter than normal) cadence sensor—without it hitting the chainstay—is right next to the spindle on an MTB that takes 2.5" tyres. The sensor works fine, even when its radius of rotation is this small.

But it got knocked out on the trail (and I had to hunt for it using its last GPS coordinates). I'd now like a more firm attachment. Ideas?

cadence sensor

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    Duct tape? Or maybe heat shrink tube? But your method with zip ties looks quite secure already.
    – Michael
    Commented Oct 25, 2022 at 15:56
  • @MaplePanda Can you move the picture to be a answer? This won't work for me, but maybe it'll help others. I'll add my own picture of the device in question.
    – Sam7919
    Commented Oct 25, 2022 at 17:01
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    +1 from me on this question, it's a real thing... I feel like some downvotes happened here from people just being "against" things. Commented Oct 25, 2022 at 18:51
  • @Sam Will do. Apologies for not asking you beforehand.
    – MaplePanda
    Commented Oct 25, 2022 at 19:38
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    Any reason why the picture was removed, it provides an enormous amount of context to the question?
    – mattnz
    Commented Oct 25, 2022 at 22:21

5 Answers 5

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This is what I did with a hub-mounted speed sensor, it should work with a cadence sensor as well:

Put the sensor in a piece of old inner tube, glue it shut using vulcanizing solution (contained in patch kits), pierce a small hole in each corner and thread zip ties through. Tie those around the hub/crank. To replace batteries, you have to cut the zipties and the tube, but since batteries last 1-2 years this is acceptable.

This solution offers only some protection against water, so the sensor should be waterproof.

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  • After trying, I now see that a road bike inner tube (23-25mm) won't fit. Just to be clear: you used an MTB inner tube, or is your speed sensor that tiny? (Come to think of it, a fatbike inner tube might just wrap around the whole crank arm, with space to squeeze the sensor inside.)
    – Sam7919
    Commented Oct 27, 2022 at 19:59
  • @Sam It was probably a 28-47mm trekking tube (Schwalbe 17). Can't say for sure.
    – Erlkoenig
    Commented Oct 28, 2022 at 4:21
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Use reusable zip ties. Just make sure you leave a little excess length to ease release/retighten.

You may find needle-nose pliers usefull. And file the sharp edges out of the zip tie ends after you cut them.

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  • Reusable velcro cable ties are a thing too - plus they're a bit softer than plastic ones.
    – Criggie
    Commented Oct 27, 2022 at 2:03
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    @Criggie possibly. The only ones I know of are much wider than desired for this application.
    – calofr
    Commented Oct 27, 2022 at 7:40
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This answer won't be for everyone, but if you use a power meter, they have self-contained cadence sensors. Power equals torque * cadence, after all. For pedal-based or spider-based power meters, there isn't a risk of failure in the mode the question describes.

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    @Sam the industry can't even decide how to make bottom bracket interfaces or how wide hubs should be. A standard for cadence sensors is pure dreaming. Commented Oct 25, 2022 at 17:39
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    The headset top caps are more or less standard, and there aren't that many handlebar diameters. What else do you need for mounting a head unit? And what else do you need for mounting a cadence sensor than a a crank arm that zip ties can go around?
    – ojs
    Commented Oct 25, 2022 at 18:27
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    +1 - the question demonstrates how bikes can't always just be clear, modular divisions between the base design and the accessories. Integrating things sometimes stops being a gimmick and becomes the only good way. Commented Oct 25, 2022 at 18:58
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    if you use a power meter, they have self-contained cadence sensors Never tried to actually use the data coming from the cadence sensor built into one of the old hub-based Powertaps, have you? ;-) (The cadence data from those was normally within an order of magnitude or three of what your cadence must have been at the time of the sample given the limits of human physiology...) Commented Oct 25, 2022 at 21:49
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    @Sam this is a good time to not have a standard (or at least to have plenty to choose from, which comes to the same thing). Would a proposed standard work on a tandem with a timing chain? A recumbent? Different applications require different approaches. Your other example of forcing the computer onto the steerer tube cap is another. It's not always going to be in the right place to read (think of a compact frame with aerobars - you'd have to look far too far down) and there are other things that fit there, from compasses to charging sockets.
    – Chris H
    Commented Oct 26, 2022 at 8:54
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Here's one solution I've seen online, which seems to involve zip ties just like @calofr describes in their answer. I will admit I have never dealt with a cadence sensor before, so can't offer any first-hand advice myself.

enter image description here

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  • This looks like the default mount of the Wahoo cadence sensor, it even ships with those tiny zip ties.
    – Erlkoenig
    Commented Oct 27, 2022 at 6:18
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If it were me, I'd make a wedge that will fit between chainstay and sensor so the elastic band is not pulled sideways by the angle. The smaller distance from the BB axle should not be an issue for the sensor. A 3dprinted part in PLA should be totally adequate.

I'd also add a short thin piece of woven cord or ribbon to tie the sensor to the crank arm as a safety line. This would bear no load normally but if the zip ties failed then the cord would stop it dropping. You'd want to secure to a closed loop somewhere on the sensor's body.

I'd also consider colouring it bright yellow or orange, to stand out in the dirt if it did fall.

Additionally, I'd also put my name and cellphone number on it to maybe get it returned. This worked for my prescription eyeglasses, saved me $hundreds on a new set. But this has never helped recover any dropped rear lights (5 at last count)

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