Insanely hard Kickr resistance

I did the 7th day of Zwiftmas today and during the power intervals my Kickr resistance got insanely hard.  The intervals called for 3min at 360W.  The first interval was fine, but for the others the resistance became increasingly difficult to the point that I was standing up in my lowest gear, at an RPM less than 50 and barely hitting 310W.  I even tried a spindown during one of the rest intervals.  I do not know if this was Zwift issue do to the number of people in the group or if it’s a Kickr issue.  Any feedback would be helpful.  Thanks!

Hi Zach. Is your FTP set correctly 360w for a 3 minute period would be very hard for most riders. If your are in ERG mode then you would need to be at a high cadence or the Kickr will start to ramp up the resistance. 

Hi John,

Thanks for the response.  I’m new to Zwift and the Kickr so I don’t believe I’ve set my FTP yet so I’ll look up how to do that.  My FTP on the road is 333W but I did an FTP test on the Kickr a few weeks ago and got 421W.  Is it typical to have that much of a discrepancy?  And is there a difference between ERG and SIM mode?  I’m using Zwift on my Mac.  Thanks John!


Hi Zach. Yes FTPs can be different. Both are very high BTW - you must be much fitter than me! ERG is used in workouts it allows Zwift to keep you at a set power if you keep the cadence the same. It explained much better than I could at the following:–How-to-use-ERG-Mode-in-Workouts

ERG is great and makes workouts much easier as in SIM mode (as normal) it would be much harder to keep to a set power.

Hope this helps.


Thank you so much.  You solved my issues with your explanation and the article.  Today was the first time I did a “workout” in Zwift and now I understand some of the problems I was experiencing.  Happy New Year!

Cheers Zach. Once you’ve had a few goes you will get the hang of it, you might need to increase cadence a bit if the power changes a lot between intervals. Good luck!

Shane Miller’s YouTube video explains the issue you’ve had AKA - Spiral of death… I use a Kickr and had the same issues.


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Thank you, Julian!