Got Powertap P1? Different crank lengths? Wahoo Elemnt?

Equipment
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Ok I think this might be as special-snowflakey as it gets, but here we go! I think I found a bug.

I sent my P1s off for a warranty repair because they were being flakey, showing me a big imbalance (8%) where there used to be less than 1% on average and one pedal always seems to have reset to an incorrect crank length setting no matter how often I reset it in the Powertap App (my roadies have 172.5mm cranks, my TT has 170). See here for that: Powertap P1(s) PSA: Use the SRAM AXS app

The service centre did find a small issue where one diagnostic value was slightly out of the optimal range and they told me about using the AXS app, that my firmware was out of date, so I thought one or more of those must have been the problem.

I got them back today, decided to check them by running TR + Kickr on my PC while recording the P1s on my Elemnt. Reported the same imbalance as before, 54/46. I’d verified their settings (172.5mm) and calibration in the AXS app before I started.

Turns out it was the Elemnt. Way back in the mists of time I set the crank length in the Elemnt app to 170mm, forgot about it, now every time I calibrate the pedals in the Elemnt it sends one of them this fossilized value! I reproduced this a few times before contacting Wahoo support.

How’s that for a weird gadget ecosystem problem?

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Yep. The P1/P2 are dinosaurs now. They’re true L/R over ANT+ but over BLE you have two independent P1S/P2S units. Could it be that the Elemnt was pairing via BLE and only sending the crank length to the single pedal?

Power pedal crank length setting can be a PIA. A head unit will override what is set on the pedal. Head units that don’t set crank length (most indoor training software, iirc) need the correct setting in the pedal.

3 Likes
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Good shout! I did wonder that yesterday while I was playing with it and it was listed as ANT+ in the Elemnt. I get left/right balance which I assume is only available over ANT+ given that TrainerRoad only gets single-sided over Bluetooth. I’m none the wiser what it’s doing under the hood with pairing, mind you.

Actually that reminds me of something else. If I zero the pedals individually in AXS I get significantly different offsets for each (difference of about 10), but if I calibrate with TR, Elemnt or Garmin I only see the left value. I assume they’re all zeroing both, but showing a single value.