Need help! Increase of wattage (ftp) after trainer calibration

5 weeks ago I got myself an wahoo kickr snap. Back then I calibrated the snap using Zwift. Today I did a 2nd calibration. First with Zwift, after that with the Wahoo app.

Before the 2nd calibration I was getting dropped very fast in Crit City races in category D and did pretty well (199 watts, 2.7w/kg) on the Alpe. Zwiftpower showed me I was a category C rider. This was mostly because of the climbs like the Alpe. I was rubbish at flat courses.

After todays calibration (did it several times after warm up on Zwift and Wahoo) I managed to become 4th on a flat cat C race and my wattages are much higher. Also all of sudden my FTP increase from 242 to 247 after that race.

Now I am in doubt If these statts are correct and reliable. I am very curious about your opinion and how I Can check if the latest statts are reliable or not. If not reliable, how to make it right again.

Thank you in advance!

Hi @Nico_Roek, welcome to the forums!

If this is only the 2nd time you have performed a spindown calibration in 5 weeks, you should probably plan to do them much more often. Wahoo recommends a spindown, after a warmup, each time you ride on the snap.

Note this:


  • Ensure the roller adjustment knob is turned 2 complete (360º) rotations once it contacts the tire
  • Check tire pressure before each ride to match the pressure recommended on the tire sidewall
  • Perform a warmup and spindown before every ride
  • Always use a slick (non-knobby) tire with the KICKR SNAP as knobs generate excessive noise and vibration
  • Use tires with a hard compound or a dedicated trainer tire to decrease wear and extend tread life
  • Tighten the roller one quarter turn (90º) if your tire consistently slips when pedaling

Also, you should use the Wahoo app to calibrate, not within Zwift, for best results.


Thank you for your reaction. Based on the information in the thread, can you say something on the reliability of the 2nd calibration?

To me it seems like something went wrong during the 1st or 2nd calibration, because the differents from 25th in crit city category D and a race in New York today were I became 4th in category C seems to big in only 3 weeks time.

Looking at your zwiftpower profile, it looks like a pretty dramatic change from a race 3 weeks ago where your average watts were 146 to today where you were averaging 249 watts.

Either your 1st calibration was way off, or your most recent one is. Your best bet is to do a spindown every time you ride, and follow all the instructions on Wahoo’s page that I linked above.


Thanks so much for you help. Will check on the provided information.

Thanks again!

A wheel-on-trainer can never display the correct wattage. Before there were direct-drive trainers, I also used such a toy. The values were always wrong. I couldn’t set the resistance hard enough because the device was overwhelmed with my watts. The tire wanted to dissolve in a short time when everything was tightened. Unsuitable for real training. Maybe useful for beginners without power.