Rapidly changing/inconsistent power/resistance, especially during climbs


I just recently started riding on Zwift using a Tacx FLUX S Smart Trainer. During a ride today I noticed incredibly spikey power graph at the bottom of my screen while riding, additionally this was also felt in the pedals (rapidly changing resistance) especially during climbs.

Having looked trough the power graph after my ride, it indeed looks very spikey. During the steepest ascents, it alternates between 300 and 80, with 1-3 seconds intervalls.

During the flats, the rapid alternations is lessened, however still mostly present. There seems to be some sections where it’s not there.

The Tacx S smart trainer have been calibrated using the Tacx app.

If you can replicate the problem riding with the Tacx app that would narrow it down to the trainer itself so you could raise it with Garmin support. This was discussed in a previous thread but there wasn’t a clear solution. If you want to rule out overheating, aim a fan at the trainer and see if it changes anything. You could also try riding at a higher cadence and see if that helps. High power, low cadence, and high resistance (higher Trainer Difficulty on a climb) will tend to bring out any overheating issues.