As part of transparency for Zwift racing, I’ve started dual recording power data for my rides. I use a Tacx Neo that doesn’t require any calibration and Powertap P1S pedal. Initial recordings below showed that the P1S read a good bit higher than the Neo, which I found unusual as DCR used these two as his gold standard for comparing powermeters:
I fully degreased my chain, cleaned up my cassette and lubed with Finish Line Ceramic Wax lube. Here’s the second set of data after cleaning up the drivechain:
Average power on both the pedals and Neo were pretty much identical over the race distance.
I’m pretty meticulous about keeping my bikes clean, but as my trainer bike doesn’t go outside the chain doesn’t get the same love as my road bike. Moral of the story? If you’re using a trainer as your power source, pay attention to your drivetrain. The losses can be significant.