Cadence incorrect - low

On two rides today I noticed cadence was lower than it should be. After the first ride I disconnected the trainer and the plugged it back in. Cadence remained low.

In the first dual recording you can see the Crank power meter correctly recorded cadence.

In the second I recorded the trainer with a Garmin Fenix and it was correct, however, it was still wrong in the zwift fit file leading me to believe it is a new issue with the app/tvOS.

Both dual recordings are posted to zwift power.

Apple TV (A1842)
tvOS 15.4.1 (19L452)
Zwift app 2.23.3
Wahoo Kickr V5 (2020) firmware version 4.2.8

Quarq DZero firmware version 10

Cadence reporting on almost all trainers, including the Kickr, is only an estimate since the trainer doesn’t have a cadence sensor (which your crank power meter does).

Your trainer will be estimating your cadence based on power fluctuations in your pedal stroke.

Zwift doesn’t do anything with the cadence data and just displays it and logs it.

So the issue that you saw isn’t likely to do with Zwift or your ATV, but your trainer. It could be that the route you were riding meant that your pedalling style made it harder than usual for your Kickr to estimate cadence.

How much of a discrepancy are we talking about here? The Kickr does a pretty good job of calculating the cadence, but it will never be as accurate as a sensor that takes exact measurements such as a pedal or crank-based power meter. If you’re just seeing a few percentages off then it’s likely just the natural variance in the calculations.

Thank you for the quick reply and explanation. It remains unclear why the Kickr has been so accurate +/-2 % for months and was 28% off yesterday. Nothing different about my pedal stroke or power. Averaged 68.7 rpm recorded by Zwift and 96.2 rpm recorded by Garmin Edge 1000 from the Wahoo Kickr V5. I’ll do another test with the Quarq batteries removed to ensure that Garmin isn’s using that cadence data.

Cadence in Zwift is meaningless, I use my garmin headunit with a full gammet of sensors and a bike on PM and most all the numbers are very close I find, when the trainer is calibrated nut on the power is only slightly elevated on Zwift but cadence is always off. Mine is usually off by 10 all the time. I can be spinning at 100 but zwift is 90 or so…just the way it is. I generally ignore all the “numbers” anyways and just enjoy the ride.