Why is my Zwift data quite a bit different to my kickr data? Aren’t they both running off my power output therefore they should be the same?
I would imaagine the kickr speed isn’t exactly derived from power, it’s derived from flywheel revolutions. That’s partly a function of power but mostly is a result of gear selection. Zwift, however, behaves more like the physical world in that speed is a function of power, gearing, wind drag, rolling resistance, weight, incline, etc. Zwift takes your power output, plugs it into a physics engine, and then derives a speed based on the virtual world.
So the short answer is no. Only rarely will Kickr sped match Zwift speed as the are arrived at in completely different fashions. My advice is to ignore Kickr speed while riding on Zwift.
Cheers for that.