Zwift w/kg with Wahoo Kickr

I have been using a Tacx Vortex on Zwift for almost 3 years without any glitches at all but lately after moving to a Wahoo Kickr, I noticed that my w/kg is constantly fluctuating and very unstable. Would appreciate any input if you know the reason why?

I do calibrate the Kickr regularly.

Thanks for your input.


Hi Pierre,
the only advice I have, is to keep your Tacx Vortex as a back up. I’m pretty sure the Kickr will not be as reliable as you Vortex.

That is somewhat expected. The Vortex is a wheel on trainer and has an accuracy of <5% whereas the Kickr is a direct drive with an accuracy of 1-2%.

Check Zwift settings to see if you have it set to instantaneous or 3 sec average power. Direct drives are more erratic with power if you have instantaneous power on as they are much more accurate.

In essence the Vortex smoothed your power even if your setting was instantaneous since it is estimating the power based on how fast your wheel is turning the drum.


@Pierre_Babeu_71_PACK: what do you mean by “w/kg is constantly fluctuating and very unstable?”

I suspect that @D_Watson_HERD_Sweep has posted the answer. If, for instance, you’re trying to ride at 3 w/kg and you’re finding that Zwift is reporting 2.7, 3.1, 2.6 … I’d suspect that you’re seeing that you are human and not a machine. If you were finding that Zwift is reporting 2.0, 7.0, 0.5 … when you’re trying to ride at 3.0, that’d be a different matter.

I had a hard time transitioning from wheel on too. I switched from and Elite Rampa to Kickr this season. I found it really makes you think of your form in terms of gear selection and cadence.

I found that I was trying to make drastic cadence changes to level out the w/kg. Later I discovered that slow, smooth adjustments were more effective. Hope this helps!