Power meter vs. Kickr

Equipment
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I didn’t want to start another new topic because my question is very close but different. I’m using an oval ring on my MTB, which is the only bike I use. After listening to the Trainerroad Podcast featuring Scott Cooper i found out the Oval chainring i’m using is probably at leasty in part, the cause of the difference in power readings I’ve been getting between the Kickr Core and the 4iiii meter.

I have been using a Wahoo Kickr Core trainer for my indoor rides using Trainerroad. On the Kickr Core i was using the internal power measurements and ERG mode and when i got my 4iiii Left only power meter I noticed it was reading a lot higher than the Kickr Core. I used the scale factor option to try and “fix” it and putting that setting on 0.94 made the power meter read almost the same numbers as the Kickr Core internal power meter.

Now for my question. I want to switch back to a round ring!
Should I put the Scale Factor back to 1 and just trust the power readings the 4iiii crankarm is giving me?

Or try and compare it with the Kickr Core again and us scale factor to match them again?

@IvyAudrain should I do a manual Ramp Test just to be sure or should the round or oval ring situation no issue?

I’m very confused :sweat_smile:

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I’d do that.

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We recommend you just undo the manual scale factor setting. :+1:

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Just to let everyone know what happened in the end. I switched back to a round front ring in my recovery week. Seemed like a good time to do it, so I could perform a Ramp test if I would have ended up with totally different readings.

I made a workout in workout creator 20 minutes long just stepping up 5% every 2 minutes. Did this once with the oval rings but with the power data from Kickr Core on TR and the power meter data on my head unit. These numbers overall still matched.

After doing that I followed Ivy’s advice and when I changed back to the round rings I put the power meter Scale Factor back to 1 (instead of 0.94) and completed the same workout again just like before. Numbers matched. :person_shrugging:t2:

Conclusion:

In my specific case the oval rings would have given me 6% higher power numbers if I hadn’t put the scale factor to 0.94 to match my Kickr Core numbers when I first got my power meter. (4iiii left only). At the factory settings and on a round ring the Kickr Core and the 4iiii read almost the exact same numbers.

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