Tacx Flux S sudden resistance spikes in ERG

I am having issues with my Tacx Flux S, where the resistance will suddenly spike during ERG workouts. It can be perfectly fine for 20-30 mins, then it will all of a sudden add a load of resistance.

Yesterday, I did a interval session where the first two sets went smoothly. I did the hard efforts as normal and dropped one gear for the easy bits. When the third set started I could barely pedal the thing during the “off” parts of the set. I had to drop to my easiest gear, but was still pushing almost 250 watts at 30 rpm :-s

Any sugegstions?

I am using an up to date Flux S (4 months old) and the latest version of Zwift on my MacBook Pro. Everything is connected through Bluetooth.

Is the indicated power also spiking up, or just the resistance perceived in the pedals?

Both are spiking. No matter how slow I pedal or how easy gear I’m in, it is almost impossible to push anything less than 200 watts, just keeping the pedals moving.

Both spiking potentially points to the communication link between the app (Zwift in this case) and the trainer, rather than the trainer itself.

Can you use an ANT+ dongle and try with that if you still see an issue? That would eliminate some possibilities.

Thanks for the suggestion. I’ll give it a shot and report back

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Just did a short steady session with the Ant+ USB dongle. The Flux S seems smoother with this setup than using Bluetooth. I’ll do an interval session within the next few days and will post an update.

Fingers crossed :slight_smile:


Wow, what a difference! The ANT+ connection seems so much more stable than BT. The resistance changes in my latest interval session were silky smooth, and for the first time, I was able to complete the whole set without changing gears (ERG enabled).

Thanks for the suggestion :+1: