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RS200 pedals steadily decreasing power over ride compared to trainer - Answered: No fault of RS200

e_tomasson
over 3 years ago

I've noticed that when I calibrate my trainer and my RS200 pedals right before a Zwift ride they are almost exactly the same at the start  but during the ride the pedals will decrease power about 15 minutes in by about 3 watts. Then every ten minutes it loses another 3 watts. After a 40 minute ride the pedals were about 10-11 watts less. (Strava noted that the pedals averaged 5 watts less overall which makes sense.) The RS200 pedals are connected to an Edge 130 plus and I don't see any issues there and the temperature was exactly the same in the room so I'm a bit stumped why this is happening. Anyone else? It's strange they stay identical for about 15 minutes or so. I can definitely feel its the pedals that are changing and not the trainer.

  • 0 over 3 years ago

    If you use your Edge to do a zero calibration after the 40 minute ride, does the power difference relative to the trainer disappear?

  • 0 over 3 years ago

    What kind of trainer do You have? I think it is the most important (because 99% of trainers are garbage)

  • 0 over 3 years ago in reply to t_smit

    Haven't tried that yet but will try tomorrow.  My best guess is that they will probably sync up again. I just watched the Gplama.com review and he had a similar problem. His theory was the right pedal for some reason was losing calibration. 

  • 0 over 3 years ago

    I had a very similar experience yesterday during a ramp test.

    I calibrated my RS200 before starting and did a spin down on my Kickr Core before starting. I recorded the output from the turbo and the pedals separately. The turbo and the RS 200 initially seemed to agree.


    When I look at the data now in TrainingPeaks I can see the right pedal ramps up much shallower than the left pedal so the effect is as the power ramps up the power report by the pedals gets further and further away from the correct value. The final minute of the ramp test reported 30 watts lower on the Rally than the Kickr.

    I am going to try again with auto zero set to no.

  • 0 over 3 years ago

    The same is happening to my pedals, I em seeing it very easily on long rides in zone 1/2. My zone 2 is 170-230W. But after 2h of slow ride I em giving only 170W to stay in zone 2 bpm…I have kickr, sworks crank power meter and Assioma duo, so I know what I em talking about. Very strange that power is decreasing a lot…also L/R power is different from training to training. One time it’s 49/51, next time it’s 41/59, last training it was 46/54. I now that normally it should be almost always the same.

  • 0 over 3 years ago in reply to ChrisJohnston

    No difference with auto zero off.

    I took another look at this today. The RS200 is always reading lower than the turbo and the higher the power the bigger the delta. 

    Are these forums monitored by anyone from Garmin CS?

  • 0 over 3 years ago

    I can confirm on a ride this morning that I lost 8-10 watts again after a 40 minute ride with average power of 171. But when I stepped off for about 15 seconds to stop Zwift (on a laptop in front of me that requires me to step off to use) the trainer and pedals were back to showing identical power readings when I started to ride again.  It didn't even require a zero calibration just a step off and on. Strange. 

  • 0 over 3 years ago in reply to e_tomasson

     Could that have been the automatic calibration?

  • 0 over 3 years ago in reply to ChrisJohnston

    Garmin have requested that I provide them with three ride files recorded on a Garmin device.

    I’m  not sure how they can see anything from that given we only know the problem is there when we are using a third party product too. 

  • 0 over 3 years ago in reply to ChrisJohnston

    The pedals will only automatically calibrate just before they go to sleep (if auto-calibration is enabled). That takes four minutes of no pedaling being detected.

    If there is a change in agreement between the trainer and the pedals, that occurred after stopping for 15 seconds, then it may have been because the *trainer* reset its zero offsets.