Assioma power 15% lower than smart trainer?

I have a single side assioma power meter pedal and a 4iiii fliiiight turbo trainer. The power meter pedal is not on the bike I use on the turbo trainer.

Out of curiosity, I put the bike with the assioma on the turbo to see how the power compares and I was surprised to see a 15% (percent not watts) difference, with the assioma being lower.

I had expected a difference but not quite that much. And I would have expected the assioma to record higher than the trainer as it measures power at the pedal vs power at the rear wheel.

Is this normal?

I’m not sure if this is normal or not, but I believe alot of smart trainers are optical, rather than, strain gauges which aren’t as accurate, as far as I know.

Yeah, normal.

My Vector pedals (dual) are 20 watts lower than the Kickr. ~ 10 - 15%

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I think the topic title should be: 4iiii fliiight 15% higher tan powe meter?

Kidding aside it is hard to say which off the two is off (could be both), but as long as they are both consistent I think it does not matter…


I’ve got an elite Drivo and I’ve just got the Assioma duo pedals and they seem to read low also. This is the same in comparison to others I ride with. I understand this is not a perfect measure but they do read low compared to feel on road and against turbo.

Do you just adjust your ftp on your head unit down by x% when you’re outside and using the pedals for power?

No - I’ve only had them for 3 weeks and most of my rides are indoors so use the trainer power. But I expected the pedals to be higher if anything.
Nothing worse than buying a powermeter that reads lower…

Can be coming from leg imbalance. I had a 10-25watts difference from the 4iiii left side power meter VS my Kickr 2020. Recently bought a pair of Favero Assioma DUO and found out it was because Im a bit imbalanced (56%/44%). Doesnt take much to see a gap if you are just slightly imbalanced.
If you really want to compare, I’d test with a dual sided power meter.


I found exactly the same and because my vectors weren’t on my trainer bike I used to run an indoor ftp and an outdoor ftp. Just got the vector 3’s so on next ramp test need to dual record and see if same situation exists.

In a perfect world, a crank/pedal based PM would read 1-3% higher(drivetrain loss) than a trainer.

The problem with comparing two sources of power is that its impossible to tell which one is correct.

The Assiomas though have an extremely good reputation, so I would trust them a lot more than the 4iiii flight. But you never know.

I have had the Duos now for a couple of weeks and they seem spot on my Quarq and Kickr20.

If the trainer is basically the same as the Stac one you can adjust the reported power on the trainer to match your Assiomas, A leg imbalance which varies can make getting a consistent percentage tricky though.

The Assioma are a trusted source and trainers are not. My FTP took a massive hit when I switched to Assioma duo, from 280 down to 258. It at least I now have a reliable and useable number I can utilise across platforms.

Using a Tacx Neo 2T which always reads 7-8 watts lower than my Assioma Duo. Probably partly due to drivetrain loss as mentioned earlier in the thread.

Yep, the Assioma do have a good rep.

For training it’s not a problem since the turbo trainer is consistent with itself and I only use the trainer’s power when training.

I was hoping to use the assioma on the road to make sure I was staying within certain thresholds. But it looks like trying to compare them with the turbo is bit tricky.

Will probably just have to on RPE :slight_smile:

I have Duo’s that read lower than my Neo. Both very trusted sources. I assumed the Assioma would be higher due to location in the movement, but no. Since I do the vast majority of my riding indoors, I adjusted the pedals to match the Neo. In the end, I’m just not willing to deal with 2 FTP’s and when I’m outdoors I’m usually riding for pleasure, not racing.

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You can scale the output of your Assiomas in their app to match your trainer.

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You could reliably adjust your outside power zones by obtaining a good average of offset % at different powers on the Assioma (for e.g. % offset at max of zone 2, zone 3, zone 4 etc. Then take the average of that figure to adjust your FTP) or if you have a smart trainer just use power match and use the Assioma exclusively?

Kinda raises the question of why you have an outside based power meter if not using it to pace?

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Only a few older Elites, like the Directo. Most current ones do not have a load/strain/torque sensor. They know the flywheel inertia and rpm. The spin down give it the drag of the trainer internals. They then guess the electronic resistance.

This is generally more accurate than measuring it directly.

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I do not have a smart trainer, but have 3 forms of PMs - Power2Max (5 years old), Powertap P2 pedal (dual sided 3 years old), and a pair of Assiomo single sided (new this year). All read within fractions of a percent. Just ride and watch consistency of the units - trainer/pedals. As an aside, the Assiomo are a much better “pedal” for normal road use than P2’s, in my opinion.