Kickr Snap suddenly drastically different in power after calibration?

Has anyone experienced this? I don’t know what my actual, real FTP is. But after using my snap and Zwift for over a year, calibrating it occasionally, my best ever performance calculated my FTP at 348. All my workouts up until this point had been working up to this, and challenging myself to best this number.

Recently, I took my bike off the trainer to clean it and tune it up, and put it back on and recalibrated again. Now suddenly I am peddling through mud to get going. I am wrecked before my warm-up even starts. With my best possible effort I managed to hit 660 watts for about 1 second before I had to quit. Before my best ever sprint wattage before was about 1100 for a few seconds. I think if I were to retest my FTP right now it would probably be less than 200 watts.

I called Wahoo and they had me do a bunch of stuff. None of it changed anything. Zwift couldn’t help either. I’m so aggravated with it that I am about to return my trainer and cancel Zwift. It’s just too frustrating to use it like this.

Has anyone else had this experience? Were you able to resolve it?

What’s the current spin-down time?

22.7 seconds? I just did one now.

That’s too long. Wahoo says it doesn’t matter on the newer Kickr’s, but it does. Try tightening the tension knob until you get the spin-down time to between 10 and 15 seconds. I"m not promising this will fix the problem, but start there.

What size and type of tire are you using? And what psi?

How are you doing the spin down test? Are you using the Wahoo app or Zwift?

It’s a trainer specific tire. Some red thing. 100 psi and 23c.

The primary issue is that for nearly a year I’ve been “training” on this thing several days, sometimes 5+ days a week. Took me months to get above 300w FTP, then 320, then 348 was the best I ever did. It’s been consistent this entire time and I felt like I was moving in a linear way. It’s so aggravating to suddenly have that all upended. I don’t know what’s real but there’s no way my best possible sprint power is 600 watts for 3 seconds. That can’t be right.

Will try tightening it up.

Tried both types of spin downs. I just lowered my FTP manually to 200w and now I’m doing Emily’s Short Mix. Maybe this is just my new reality. It’s much less aggravating now that I hit my stars.

I feel your frustration! I went through the same thing while I was figuring how to work with the SNAP and get consistent power readings.

Just a side note… an FTP of 348 is pretty high. What is your cycling experience, and how big of a person are you?

Tire and pressure sound fine. Try cranking the tension knob until the spin-down time is under 15 seconds. It does make a difference.

I put a mark on the tension knob so I tighten it to the same position every time.

Only use the Wahoo App for calibration. I have never had good results performing a spin-down calibration from within Zwift.

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A couple of other ideas…

  1. Do you know anybody with a power meter? Pedals would be easiest. Install those temporarily and see how well they agree with the SNAP.

  2. An “Advanced Spin-down” is still possible. Did Wahoo support have you perform one? If not, contact them again and ask how to do it.

I ride a lot. I weigh about 170. I dunno how strong I really am. I don’t race. I survived a 160 mile gravel ride with 10k climbing in January but it took me 14 hours because I bonked. I have a few cups and one not very impressive KOM in town (Tucson) on Strava. Strava always estimates my average power for a ride to be between 150 and 250 watts for a ride of around 50 miles or so. Shrug

You know, I just reset my FTP manually to 200 watts and was able to finish my workout without rage quitting because at least I was hitting my “stars”. Maybe I’ll just adjust to this new reality.

As you’ve discovered, consistency is key. I’m not sure what caused the big change in power readings.

Do try to get the spin-down time between 10-15 seconds. It has been noted that the SNAP reads power on the low side if spin-down times are too long.