Smart trainer reports 0 watts when downshifting


Picked up my first smart trainer recently, a wahoo kickr snap, and I’m trying to figure out how to properly use it after riding on a classic trainer with a speed sensor. ERG mode workouts work great but I’m not really sure how to best use the new trainer in free rides or racing.

I believe I have to use my gears to increase or decrease the tension and therefore watts. When I shift into a harder gear I’m able to lay down the additional watts I’m hoping for. When I shift into an easier gear to try to rest or whatever things get a bit weird. The trainer is dropping the watts to about 0 and then will gradually build them up to something reasonable.

Is this drop to 0 normal? Is there a way to avoid it by doing something or is there something wrong with my trainer? Worried that I could easily get dropped in a race if this happened. Thanks for any thoughts!

Correct, you can also increase cadence to get more power in the same gear (unless you are in an easy gear and you start to spin out).

When you go into an easier gear do you feel any resistance or is the trainer’s flywheel spinning too fast and taking a while to catch up to your easier gear?

Have you done a spindown calibration using the wahoo app and made sure it is installed correctly on your rear wheel with enough tension? Also make sure the rear tire is inflated to the proper psi per manufacturer.

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I would say it does feel like this. If I’ve been holding a high wattage for a few minutes I’ll often want to reduce effort so I often shift into an easier gear. It might be that the flywheel is still spinning fast from the previous effort. Is there a way to prevent this problem? I’d obviously likely to get credit for any work I’m doing.

I have done a spindown using the wahoo app and I believe it is install correctly. The tire is inflated properly and I have enough tension on it that I don’t feel it slip even when sprinting. I suppose I could tighten it more and see if it helps…

I don’t think so, it is similar to being outside and riding IRL. If you do a max effort and then shift to an easier gear your momentum will carry forward and you wont produce any power until the bike slows down a bit. You will coast essentially.

I don’t think tightening the knob on the rear tire will help?

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To show watts as you slow down, try easing up on the cadence in the high gear and then shift to a lower gear.