Difference FTP changing trainers

I did a 20 minute test 2 weeks ago on my kickr snap. 270. Ramp tested on my new saris H3 a few days ago and got 232. Is such a differential normal between trainers? I’m not hung up on the number just don’t want to be under achieving by riding workouts which are too easy.

Also if it’s accurate it means I can’t race in the correct category in Zwift. It puts me around 2.5wkg which will kill my in the Cs :pensive:

Quite normal and I’ll even say expected. There’s a massive difference in the flywheel size and effect related to your pedaling motion. You also should consider the gearing used between each trainer and test (same or different). Add in the need to also consider the trainer mode you used (RES, ERG and such).

And all that before we even talk about power data accuracy. Calibration practice matters and the fact is that despite claims, we see wide differences between devices in some cases. Your info and all these potential factors are why it’s good practice to retest FTP whenever swapping a trainer or power device.

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I suffered the same blow to my ego’s FTP when I went from a Tacx Vortex (wheel on) to a real power meter.

After a lot of testing I found my Stages power meter, my Kickr, and a Powertap hub were all within 10 watts of each other. My Tacx Vortex would measure anywhere between +25 and +75 watts depending on how warmed up it was and what intensity one was riding at.

The good thing is that you are going to love your H3 compared to the Snap.


Yes its very normal @novemberdelta you are also comparing two different FTP test methods which will exasperate things. For a 20mins test I’ll hit a number similar to you and for a ramp test similar numbers too.