Power Meter Discrepancy: pedals vs. trainer

I’ve been using a Wahoo Kickr Snap (wheel on) for a long time using Erg mode and Trainerroad. I just bought Favero Assioma Duo-shi PM for my outside rides/training/etc. I wanted to compare the differences in power between the two units. Last night, using Trainerroad and the Wahoo Kickr in Erg, I compared it to the Assioma pedals connected to my Wahoo Roam head unit. Significant differences! During the SS intervals, Trainerroad read ~240 watts and the pedals were about 20-30 watts higher (260-270 watts). During the rest intervals, Trainerroad/Kickr reads 108 watts and the pedals read 150-160 watts!!!

Any thoughts on the significant difference here? To add: I did calibrate the pedals per the instructions and perform a spin down on the trainer before every workout. I also pump up the tire to ~110psi every time.

Any help is appreciated!

Pretty common, pedals will be higher due to no drivetrain losses. Also common for different powermeters to just read power differently. I’d do a ramp test with power match, and use the Assiomas as your new source of truth inside and outside.


There’s dozens of similar threads on the forum, just pick one source and go with it. I’d go with the Assioma’s just because you can use that source inside and out and on different bikes.


Use the pedals as your source of true power and just use the trainer for resistance. Congrats on the ~30w FTP increase!


I compared my garmin rally xc to my Tacx Neo a few weeks ago. Tacx app has a workout that’s 20 mins long of different intensities to compare power which is nice to have access to.
They didn’t match up, best thing to do is use the pedals for 1 number. It sucks changing pedals all the time but it’s better to have 1 source to rely on.

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FYI: Wahoo recommends the spindown AFTER a 10 minute warmup period, not right at the start of riding.

Suggested frequency

To calibrate your KICKR SNAP for the most accurate readings, you should perform a spindown using the Wahoo Fitness app for iOS or Android. A spindown is recommended after a ten minute warmup, and before every ride, race, or workout. Although some 3rd party apps like Zwift can perform spindown calibrations, Wahoo always recommends using the Wahoo Fitness app for best results.

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Does trainer calibration matter if using power match?

Hopefully not. I probably stopped calibrating my trainer regularly in 2020!

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The cool thing is that your FTP was higher than you thought!

Now you have to use one power meter indoor and out for your training. You also need to retest your FTP on the pedals.

Also make sure the Assiomas are getting the correct crank length.

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No, per TR reps it is not necessary to calibrate the trainer when using PowerMatch.


Unfortunately, this is common even if you do everything right. Initially, my Elite Suito’s power numbers agreed almost perfectly with my Quarq’s. Since I use power match, I only used my Quarq’s power numbers for training. Out of curiosity I checked back after a year or so. I calibrated before and after workouts (where my trainer was warmed up), but the offset and the slope were different. Ugh.

This was not good for my obsessive-compulsive side. However, there was no good way to solve the issue, bar buying a pair of Assiomas as a tie breaker. And even then, all three power meters might disagree. If a friend with a bike that has a built-in power meter is willing to lend you his steed, you could also get a third opinion that way. But the result might be that all three power meters disagree in different ways.

Instead, I just decided to stick to my Quarq and base my training off of its power numbers for several reasons:

  • I am basing my power numbers on the same measurement device indoors and outdoors, i. e. I have consistent numbers.
  • Use power match with TR.
  • Quarq power meters (like Assiomas) have an excellent reputation for just working and producing good numbers.
  • Track times on Strava segments. If e. g. you have to produce way more power on a segment for a time that is the same as before (assuming your weight hasn’t changed significantly), then something may be up. If times improve over time as your FTP and other performance markers improve, it is an indication your power meter is ok.
  • There is no easy way to determine what unit produces correct numbers.

thanks everyone! I appreciate the help and insight. I’ll retest using the Assiomas and use power match going forward.