Finally rode with the PM pedals on the trainer. Easy recovery ride.

right out of the gates the trainer reads 20-25w less. 130 vs 150.

let it warm up a bit and do an auto calibration- 5 seconds of freewheeling, the difference is cut in half. ride some more and do it again - 5w difference, within the margin of error, difference from the drivetrain loss.

If I don’t do the auto calibration the trainer feels like mush, and would stay that way the entire ride.


Zwift says 141w for the ride, PM says 162 - both average power.

Trainers usually do require a warm-up period before accurate calibration. So I would say that is probably normal.

I would also check the power at various steady state power intervals eg 100, 150, 200, 250, 300W and see if the percentage error is consistent across the power range. With drivetrain losses it should be in the order of 3-5% lower on the trainer vs pedals.

Also take into account the methodology being used. When I load my Zwift file into RidewithGPS I get a slightly higher average power than with Zwift. My calories are always higher in RWGPS too. I think it has something to do with how it treats zeros, or those times you stop pedaling, even momentarily. Since RWGPS also tracks outdoor riding I just use that as my counter.

I haven't checked my PM pedals vs. my trainer in a while, maybe I'll do that later today when I get on it.

When I bought my 1st gen Kickr and joined the Zwift beta back in 2015 (I think), my wallet sure hurt. In hindsight, that was the best investment I've made in my cycling fitness short of the bicycle itself. Living in the upper Midwest, I used to get out of shape every Winter and have to essentially start all over again in the Spring. Now I don't miss a beat all year long... although that first real-life Spring ride is always a bit of a shocker as I have to experience head winds and bumpy roads. :p