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9.75 software recording incorrect mileage by factor of 3

twonks
9 months ago

Hi all. 

Had a search and couldn't see anything exactly like my problem.

Have an Edge 530 which has worked perfectly for 4 bikes since day one.

The last two rides, it has got the distance covered wrong by around a factor of 3 (too low)

The map plots ok in Garmin Connect and it uploads to Strava but, I need to use Strava to correct the distance - which it does.

I wonder what Strava uses to calculate distance - is it something in the file or from the map - either way there is something in there that is corret, it just doesn't display as such without user intervention in Strava. Distance still wrong in Garmin Connect app of course.

Anybody had anything similar?

  • 0 9 months ago

    Strava recomputes the distance using GPS data unless you mark it as an indoor ride.

    Is the Edge paired to a speed sensor or is speed/distance coming from the GPS data?

  • 0 9 months ago in reply to aweatherall

    Thanks for the comment. 

    I spoke to Garmin via web chat and they had a look at my ride detail. 

    The file was full of errors, with a speed sensor  from my bike and the GPS Garmin data fighting over priority, losing chunks in the process. 

    This has not happened before so I guess an update has turned the bike sensor on or something. 

    I’ve now stopped the Garmin reading the speed sensor so will see if all back to normal next ride. 

  • 0 9 months ago in reply to twonks

    It is better to have a speed sensor, assuming it's in good working order and reliable.  The more twists and turns there are, the more GPS will cheat you out of distance by cutting the corner.  This is especially noticeable with mountain biking as we often have switchbacks.  GPS only pings at intervals and connects the dots, so that is how the corners get cut.

    I have a Garmin Speed Sensor 2 and my buddy has a Wahoo speed sensor.  We both get the exact same mileage within 1/10 mile each ride, even on mtb rides with lots of twists and turns.  It is also best to manually roll out the circumference and enter it manually, it makes for a very accurate  recording.

    Also, keep in mind the "speed sensors" are really just counting revolutions, then using math to derive distance and speed.  Very simple devices that are very accurate if you plug in the correct circumference by rolling out the wheel next to a tape measurer.

    A final caution... I once accidentally connected my sensor with BOTH Bluetooth and ANT+ to the Garmin head unit and that caused a similar issue to what you describe.  Only connect via one protocol.  Generally ANT+ is the preferred protocol to connect to the Edge with.  Double check that the speed sensor is only connected by one.