I have a Tacx flux and a 11 speed shimano ultegra cassete and most of the time the cadance viewed on zwift is accurate but when I climb for example and cycle in low gear the cadance is not right. Some times zwift says 40 and I know it has to be above 80 at least…
There could be a few things at play here, so I’ll try to address them for you succinctly.
It could be that the communication between the game and your trainer is causing issues with the way the cadence is being transmitted, so I’d like to ask if you can check your signal strength for your trainer connection. There is an article on our support site that will help you with specifics if you need.
You can also try changing your connection type. If you’re using ANT+, you can try Bluetooth via your machine’s native Bluetooth or via Zwift Companion. If you’re on Bluetooth, ANT+ might help as well.
If those steps don’t help, I would like to ask you to write into us at support@zwift.com and send us your game log files so that we can take a deeper look for you. Instructions on finding those files are located here on our support site. You can ask for me, Flint, or any other of our other agents would be happy and capable to help you as well.
I am thinking of something else, The Tacx flux does not actually have a cadence sensor, the trainer calculate your cadence by looking at the dead spots on your pedal stroke, so at high cadence and low gears it can be inaccurate if you have a very smooth pedal stroke.