Neo 2 vs. P1 pedals issues--I need some help

Hey everyone, I have noticed a discrepancy between my Neo 2 and my P1 pedals, so I did a test:

Here are four files comparing my Neo 2 and the P1 pedals that I have. Obviously, I need a tertiary crank-based power meter (looking at the 4iiii dual Podiiiium but will have to wait to Christmas) to see what is actually going on. First one is a 20min warmup, (after which I zeroed the P1 pedals), 2nd one is erg mode in small ring/5th gear down on the cassette on the Tacx app, (no zeroing between rounds), 3rd one is erg mode in big ring, 4th one is on Zwift with Zwift record power over BTE and my Garmin tracking P1 pedals over ANT plus. I tried to keep cadence close to 95 during tests 1-3, but on Zwift this was harder.

I hope you all can make sense of this. Which power meter should I use in Zwift (I will lose a lot of watts if I do)? Which one do you think is more reliable? Should I contact Garmin to see if I can get a replacement? Is this normal?

My observations: an expected ~6 watt difference between them in small ring. In big ring, larger wattage difference and increases over with higher wattages. On Zwift, huge difference. This was free ride mode with threshold surges and a tempo section at 300 watts.

Oh for what its worth, no issues with my gen 1 neo and the p1 pedals, and when I had a quarq red, small difference between pedals and crank but consistent and only 3-6 watts. Unfortunately, I do not have either right now to do more testing.

warmup: https://analyze.dcrainmaker.com/#/public/34a8ff91-101e-47ba-68cc-f179cde9bcae
part 2 small ring: https://analyze.dcrainmaker.com/#/public/7798d2b8-c7e8-40ed-7c8a-ef8048c0e535
Part 3 Big ring: https://analyze.dcrainmaker.com/#/public/c6fb584c-43a7-4c71-423f-dce15a2fbe9c
Part 4 zwift:https://analyze.dcrainmaker.com/#/public/efca4af3-c433-4ba4-4058-c05c8933796d

Hi
I have looked at the data. The main thing is they are tracking together. There is some where in DC rain maker telling the difference in some reading power meters. Pedals are measuring the direct force from your foot, there are then losses in the the transmission 5 watts small ring its about 7 watts in the big ring approx. There are then how accurate the power meters are 1.5% would be fair. If one power meter is reading at the lower end -1.5% and the other power meter is reading at the high end +1.5% at 200 watts that’s 6 watts difference. I have no idea what the Zwift is doing. The main thing i observe is its all pretty good data. Within 5 - 7 watts, for TR workouts good enough.

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Welcome to hell. Check the chain, chainrings, chainring bolts, cassette, bottom bracket bearings, crank tension/preload, even the rear derailleur b-tension screw can influence power between pedals and the trainer. The problem with the P1 is you can’t do a static weight test (that I know of?) to ensure they’re within spec (well, for the static test).

RE: Big/Small ring. Most trainers will be well outside their power accuracy spec at very high flywheel speeds. ERG in the 53/11 will result in huge power errors. The’ve addressed this a little with a firmware update for the 2T… maybe for the 2 as well… I’m not sure.

The answer is always more testing with more meters. That’s likely what Tacx/Garmin will ask for. Without a solid data set showing it’s the trainer at fault it’s really easy for them to dismiss the issue as being pedals and/or drivetrain.

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Thank you! This helps greatly!

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Thank you! So if I read you correctly, I need to get at least 4 more power meters :slight_smile:

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Preferably bought through links on his site :wink:

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