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Intermitent speed recording with magnetless sensor

I recently installed the magnetless speed and cadence sensors on my new bike. I could pair easily with my Edge 500. During my first ride, speed recording was intermittent, sometimes showing zero or values clearly wrong. The cadence readings seems to be ok.

I returned the sensor to the LBS and they gave me a new set. The problem still persists. Is there any compatibility problem with 500 or am I just very unlucky to get two different units with the same problem?

Tried to:
- flip the sensor direction;
- approximate the Edge unit to the sensor (when trying with the bike mounted on a repair stand).
- remove the battery, wait 30 seconds

No improvement.

I've also measured the battery voltage using a multimeter, it shows 3.02V.

Do someone have a clue of what may be happening?

PS: On my other bike, with conventional sensors, I get correct readings using the same Edge 500 unit.
  • Which hub did you put it on? Did you try the other?
  • Thanks for the reply. I put it on the rear hub. Haven't tried the front yet. I'll try, but is the sensor's range too limited that it makes difference the hub you use it on? the distance difference is very small...

    PS: I don't have any other electronics on the bike (dynamo hub, electronic shifting, lighs, power meter, etc)
  • I had the same problem but it went away after a couple of rides. There was a thin coating of a grease like substance on the battery that I wiped off. I think that was the problem but am not sure. It was always on the front wheel. Others had found moving from the back wheel to the front fixed it. It has been suggested that a magnetized part near the sensor may cause problems because the speed sensor detects the earth's magnetic field.

    But maybe it is something totally different that goes away on its own.
  • Thanks for the reply. I put it on the rear hub. Haven't tried the front yet. I'll try, but is the sensor's range too limited that it makes difference the hub you use it on? the distance difference is very small...

    PS: I don't have any other electronics on the bike (dynamo hub, electronic shifting, lighs, power meter, etc)


    It's not the range, but the amount of stuff between it and the head unit that might be the problem. The signal is weak and easily attenuated, especially by water (you and/or water bottles).
  • Today I could record a video showing the problem happen on the repair stand. The quality isn't good, but it's possible to see the speed at zero, 1km/h, 2Km/h while the wheel is turning obviously much faster then that. The cadence works ok: https://www.youtube.com/watch?v=jloy0NgamKY
    The problem is intermitent, I couldn't determine yet when it happens, but it seems to appear only at speeds above 50km/h (although once started, it may continue to speeds bellow 40km/h).
    I replaced both the speed and the cadence sensor's batteries before recording.
    As you may see, there is almost nothing between the Edge Unit and the sensor (it was placed at the bottle cage)
  • If you can post the FIT activity file that captures the speed problem I will take a look.

    What other devices are on the bike? e.g. a power meter.
  • Hi Alan,

    Here is a small .FIT that shows the problem (clearly, there is a time when the cadence is high and the speed is low).

    Many thanks for your help.

    Daniel

    PS: There are no other electronics on the bike.
  • What is the wheel size set to under the bike profile. Is it set to manual or automatic? If it is automatic I would suggest setting it to manual.
  • Tried that (manual wheel size). Problem still persists, at least on the repair stand and rear hub.
    I've decided to try the front hub, but that can't be done on the repair stand, as I can't spin the front wheel fast enough for any useful test.
    Went out for a 25Km ride, no glitch at all.
    It's not conclusive yet, but let's assume the problem only occurs on the rear hub. What would be the cause?
    It's not the distance, I'm sure, because I tried to place the Edge unit very close to the rear hub and the problem didn't disappear.
    TIGERMOUNTRIDER suggested it may be a magnetized part problem. It's unlikely, as the wheel is brand new and I never placed a magnet or any other sensor on it.
    As I've told before, there's no other electronics on the bike. What would cause the sensor not to work well on the rear hub? Anyone have a clue?
  • It could be some slight magnetization of the chain or the crank arm.