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Garmin 1040 inaccurate speed reading

carbonsteve
3 months ago

I have had three Garmin 1040 and had to send all three back as they all had the same problem an inaccurate speed reading whilst riding, when i was going along a tree lined or even low bush roads the speed would jump from 20mph down to 10-12mph and bounce about until i got to a clearing, i have to stress this wasn't densely overhanging trees but low to mid brush, and only when on a clearing did it read at a constant, this happened on every ride and i still have my Garmin 1030s and used both at the same time and the 1030s never had a drop of speed infact never had a problem with it at all so i am able to compare the bad 1040, i have now had to buy a Karoo 3 which is perfect as i couldnt ride with a unit as bad as this

  • 0 3 months ago

    Sounds like multiband gps wasn't enabled.

  • 0 3 months ago

    Why not using a speed sensor? It is inexpensive, and you can never beat the accuracy of the distance measured by the speed sensor (assuming properly calibrated) with data from GPS.

  • 0 3 months ago in reply to trux

    Even with multiband and a speed sensor I seem to suffer from the same issue. As if the gps has priority over the speed sensor. This weekend, I was going down a hill with 20km/h according to my EdgeSlight frown while it should have read more than double. My precious Karoo 2 had the same issue so I hoped the multiband GNSS of the Wdge would solve it but no luck Slight frown  So I have a faulty Edge?

  • 0 3 months ago in reply to pdj-84

    Where is your speedsensor mounted? Back or front? (Back might be problematic due to magnetic chain.)

    To check if the speedsensor is connected, turn the wheel with sensor while standing still. There must be a speed reading according to wheel speed.

  • 0 3 months ago in reply to mcinner1

    It’s on the hub of the front and reads fine when tuning the wheels. 

    My other bike, without sensor, suffers from the same issue : irregular speeds readings when below (some) trees. 

  • 0 3 months ago in reply to pdj-84

    Make sure to calibrate the sensor manually. Do not rely on the auto-calibration. And make sure it is connected, before you start the ride.

  • 0 3 months ago in reply to trux

    I’ll give that a try. With auto-circumference it seems it’s basically just using GNSS (which strangely isn’t that accurate as advertised)

  • 0 3 months ago in reply to pdj-84
    pdj-84 said:
    So I have a faulty Edge?

    More probably a faulty sensor, or incorrectly mounted, or uncalibrated, or losing the connection, or needing a new battery.

    In your place, I would concurrently record the ride for example with the Strava app, having the sensor connected to it too. After the ride you can compare both activities, and perhaps see where the problem is coming from.

  • 0 3 months ago in reply to trux

    That makes sense but nonetheless, I also have issues on my other bike without a speed sensor. Just a tiny bit of tree lines or coverage and my speed becomes irregular 

  • 0 3 months ago in reply to pdj-84
    pdj-84 said:
    GNSS (which strangely isn’t that accurate as advertised)

    Do you see any significant errors on the track, when you inspect the activity map? Open it in Garmin Connect Web, use the option "Save as Course" and check the distance it shows there. Unlike the activity that shows the distance measured by the sensor, the activity saved as course shows purely the GPS distance. So if the course distance is significantly different than the activity distance, there is a problem with the speed sensor.