Weird behavior with Powertap P1 Pedals

A bit off topic but kind of relevant. I’ve got P1 pedals and always found that they read about 6% lower than my gen1 Kickr. I’m using powermatch and taking the hit on the lower FTP so that I can get consistent figures from the trainer and on the road.

A quick search found the following paper about the P1 pedals power readings, suggesting from the abstract that they read about 2-7W lower than an SRM meter across a variety of power ranges and cadences.

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P1 has latest updates installed and that 10w difference was constant through out that TR workout. Every interval, every recovery. Even avg and NP power had that same 10 w difference.

I have 2 Quarqs, P2M NG and Neo and they are within few watts of each other. P1 is outlier.

How does that work out when looking at the stated tolerance ranges for each PM?

They are usually +/-1.5%, so is that within the range if you consider the P1 is on the low end and the others are high?

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That was my comment as well, however 10 watts is a bit outside of the combined tolerances of the P1 and Neo - especially if the 10 watt difference was consistent across the board.

@Petteri if you take into account @stueyboy comment, then the 10 watts (accounting for the margin of error) would explain it. At least it’s consistent so you can account for it, however not ideal to have to do that.

I’ll have to make a note of this - I always assumed in the past that everything else read high, not that that P1’s were low.

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Contacted TR support about this. Not very helpful. They recommended me to talk to PowerTap. But based on link that @Scorpion756 shared, I know what PowerTap is going to say.

:exploding_head:

Just tested my P1 against an NgEco and they were within 2 watts up to my ftp, the outlier was a gen 1 Kickr. I think both meters are ± 2% spec, and I know the Kickr is likely to be high, I think you’re just unlucky that your pedals are right at one end of the spec.

@JohnDFellrunner

did you try via BLE?

I used ANT for the P1 because I know that I am left heavy below FTP which would show higher power via BTLE. About 50/50 at FTP but did not want to confuse things. BTLE for the NGEco but they are only one channel

All other PM´s are within 2% of each other. P1 are reading 3% lower than second lowest PM that i have. Even when pedals should read higher than spider/trainer based PM.

I guess it is what it is. It´s not the end of the world. Just a minor annoyance. :grinning:

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