https://singletrackworld.com/forum/topic/smart-trainer-and-power-meter-power-discrepancy/
I’ve just got a Tacx Flux 2 and gave it a whirl this afternoon for the first time. I’ve also got a 4iiii crank power meter and comparing the Flux power reading to my 4iiii via my Garmin there was a consistent 20 – 40 watt under-read of the Tax vs. the 4iiii/Garmin. Is this normal and a function of the fact the 4iiii is measuring power at the crank and the Tacx measuring it at the wheel? a bit like cars on rolling roads where you get a flywheel power reading or an at the wheels power reading? or should I expect the reading to be the same?
I’ve got my Garmin set to sample the 4iiii power over 3 seconds to smooth out the power fluctuations and can’t seem to set the Tacx output in the same way so the tacx fluctuates more, but still getting a sizeable discrepancy with both 4iiii and Tacx freshly calibrated. I’ll look into it.
My Tacx Flux would read about 15-20w lower than my Stages.
For the first few months I just did my FTP tests and TrainerRoad stuff using the Flux. It meant that my FTP wasn’t ‘right’ for outdoor riding, but I wasn’t doing structures intervals outside so it didn’t really matter. Now I use the PowerMatch feature in TR to control the flux from my Stages.
What are you using the trainer for?
I have quite a discrepency on mine – bepro pedal reads something like 8% higher than the kickr core. Seems consistent so it’s not a hindrance for training (as said), but it does give me two different power regimes when I’d prefer to just have one.