TimothyH

I have a hub mounted Garmin speed sensor for use with Edge, the kind pictured below. The rubber bands on the sleeve are too long for the small diameter hubs on one of my bikes. Both front and rear hubs are only about 3/4" diameter and the sensor sleeve fits rather loosely around the hub. It grips okay in the dry but slips in the wet as the wheel rotates resulting in lower than actual speed readings.

Can anyone recommend a speed sensor which will work with Garmin Edge which might fit tighter around a small diameter hub? I don't want magnets or wires.

WheresWaldo

Although it may not look as aesthetically pleasing as just the rubber strap, You could get something like 7 or 8" long Zip ties and wrap it around both hub and sensor, It along with the rubber cover should help keep the sensor from moving without over tightening the zip ties. Any Harbor Freight or Northern Tool will have them cheap.

TimothyH

Thanks @WheresWaldo.

Zip ties are not going to allow me to remove the sensor to clean the bike as often and thoroughly as I like. I'd like a second sensor anyway so that I don't have to swap the one sensor between bikes.

For now I wrapped the rubber bands around the bub twice. Had to get my hands between the spokes, pull the rubber bands around the hub twice with the tips of my fingers... was a PITA.

andr0id

Cut a short bit of inner tube and wrap it around the hub under the sensor.

You get extra points for neatness.

TimothyH

I really appreciate all the workarounds but they are just that, workarounds.

The solution I am looking for is a sensor that fits a small diameter hub. If anyone know of such a thing, please post.

Thanks.

Athens80

Can you use smaller O rings on the same sensor?

Looigi

AFAIK, the Garmin sensor is the only accelerator based wheel sensor that straps onto the wheel. All the others I know of use a spoke magnet and sensor strapped to the chainstay or fork leg. Is you're rear hub fatter? It might work well there. Otherwise, IMO, the "cleanest" solution is to use a shorter o-ring or put a spacer under the existing o-ring. There are rubber spacers used to adapt lights, reflectors or cyclometers to different size seatpost or handlebars. One of these, perhaps trimmed to length, might work well.

John_V 

Rubber tubing works great as a spacer. Cut and trim it to fit between the sensor and the hub.

JohnJ80

There is another sensor from Velocomputer that would work with an ANT+ set up. But it's got some issues if you need BTLE support. I have one and tried it, got it to work by itself but had some conflicts with other sensors. I was primarily looking at it for BTLE support but it supposedly is ANT+ qualified.

Also, Wahoo Fitness should be releasing such a sensor by spring (rumors). It would just be a software mode on the RPM cadence sensor they have already.

The other alternative is to get the Wahoo rubber piece that holds the RPM cadence sensor to the pedal with zip ties and put that on your hub. There are also removable zip ties you can get so you could put it on and off as many times as you wanted. That's what I'd do if you had a desire to remove it. I'm pretty sure it would fit the Garmin sensor.

The final thing you could try is to put a twist in the strap on the Garmin sensor to take up some of the slack.

J.

fietsbob

add duct-tape* then put it back on .. it wont be so shiny polished under it then.

* or double stick tape or hot melt glue, etc.

TimothyH

The Garmin speed sensor does not use an accelerometer. It uses a magnetometer against the Earth's magnetic field.


Thank you for this John. The Velocomputer sensor's mount is what I am looking for. $50 is pricey though.

I've wrapped the Garmin mount around the hub twice and was thinking of twisting it to take up some slack as you have suggested.

JohnJ80

Wahoo has a shoe mount for their RPM sensor that should fit the actual sensor piece in the Garmin wheel hub mount once it is removed from the rubber mount. The Wahoo shoe mount is rubber and mounts through holes through which one can run the laces of the shoe. I used those holes with zip ties to mount it to my cranks. Since the hub is much more protected by the spokes, you could use the hand releasable zip ties cut to length to make a very nice mount for your sensor that would be much more svelte than Garmin's rubber housing. In fact, I'm glad you brought that up, I'll give that a try in the spring if Wahoo doesn't release their wheel sensor.

I didn't know the Garmin sensor used a magnetometer instead of an accelerometer so thank you for that information. I'm actually surprised by that, the cost of accelerometers has been driven into the dirt by their inclusion in smartphones to the point where they cost less than a quarter a piece. Magnetometer or accelerometer aside, I am really happy to see the demise of the Hall Effect sensors that have been in use for decades with all their alignment and proximity issues. Been waiting for that for a very long time.

Both Wahoo and Velocomputer are using the Nordic Semiconductor part that contains the CPU, memory, radios and software stacks for both BTLE and ANT+ and transmit on both protocols simultaneously. Both devices readily come up and answer to the utility that Nordic supplies to modify the flash memory on board.

I have one of the Velocomputer sensors and don't think it's ready for primetime although it's promising. The mount has some really nice features like it's size and it's bevel/radius mounting to the hub. However, the ladder-like rubber strapping is a bit fragile and easy to break. That's why I think getting your hands on the Wahoo rubber shoe mount and using that to mount to your hub with hand releasable zip ties would solve your problem and be a very clean solution. The Wahoo shoe mount quite robust but not nearly as large as the Garmin mount and it and won't break or tear.

J.

Looigi

Interesting. That's contrary to what I've read/heard. If the wheel's axis was parallel to the local field, which could happen near the geomagnetic equator, then you'd get no reading. Where did you get that information? Of course an accelerator would work against Earth's gravitational field, which would work reliably everywhere on the earth.

WheresWaldo

I would also be surprised if this were actually true, I think DCRainmaker even said accelerometer when he did the initial write up of these just prior to release. No offense to @TimothyH but without documentation I would believe what Ray publishes.

TimothyH

See the link at https://www.bikeforums.net/tandem-cyc...l#post17923917

TimothyH

That's actually pretty cool that the cadence sensor mounts to the shoe instead of the cranks.

Thanks for the feedback on the Velocomputer mount, especially the rubber strap being fragile. I saw that it said "50% stretch" in the instructions and wondered.

The Garmin sensor has a hook that sticks out of the actual sensor onto which the rubber strap attaches. I'm not so sure that the hook would allow it to fit into the Wahoo carrier. Even if it did fit, for now based mostly on price, I've decided to get a second Garmin speed sensor and just wrap it around the hub twice like I've been doing.

I want to thank all of your for the time you took to respond to my question. It means a lot to me that you did. I hope you all have much peace in the new year.


-Tim-

Dman1234

i realize this is an old thread.. but i ran into this problem with my recent purchase of a garmin 840
The speed sensor was to big for a mid 80 miyata touring bike hub.
I finally found a good solution for me ..like others i found wrapping an old inner tube around the hub many times.. taping it down and then applying the sensor with one final zip tie to make sure it stay still worked well.

Troul 

for the opposite issue, what are the solutions for using a wahoo speed sensor with a dynamo hub?

Steve B.

The sensors need to be able to wrap around currently built hubs, which are wider then old stuff. Thus you adapt when you have old stuff and put a shim around the hub to make it work,