First training in Zwift, can't be right or is it?

Hello, I am new to Zwift. Did some rides in Watopia and London and now I want to start following a training program “6 week FTP builder for beginners”. I am using a Tacx Flux S which is calibrated from the Tacx utility. Zwift already established that my FTP is 150.

On the first day you start easy with a warmup 67 w at 85rpm. Doesn’t sound like much but it is the “foundation” and you’re supposed to train mostly in zone 2. So I guess that should be right.

However, If I pedal at 85 RPM, the wattage shows as 145W, more than double what I am supposed to do. See screenshot. Is there something wrong here?


Hi @Bob_Eager welcome to Zwift forums

Couple things - your screenshot of the Companion apps shows that ERG mode is on. This is what you’d see if ERG was shut off:

You can also verify in the game app that ERG is off here:

Would you confirm that your trainer is paired for as both a power device and and as a controllable device? You have to pair power first before the controllable device is pairable.

Lastly - when selecting a workout, is the “Use ERG Mode” radio box selected?

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TacX Flux has a minimum power range for different gears. My friend has one which I borrowed for a while, it seems that to hit wattage below 100, you have to pedal at a pretty slow cadence at your lowest gear.

Here is a graph from TacX explaining the situationimage

OK Zwifters, thanks for the replies. Trainer is paired as a controllable devics, for cadence and power. ERG mode is on (as it should be for a structured training, right?).

I think the answer is in the minimum power that the Flux S handles at a certain cadance. In the graph you can clearly see that when you pedal at 85 rpm the power is about 145 Watts, exactly as in the screenshot. So Drabir Alams answer is correct. And Zwift and my trainer is working correctly.

The thing is, the program wants you to pedal at higher cadance as part of the training. If you go to slow it will prompt you to PEDAL FASTER.

Is this a shortcoming of the Tacx Flux S or is this common with smart trainers? Seems that you cannot work around this. I am already in a low gear (small ring at the front, big at the back).

I dove a bit further into this. On the Tacx website, where the power graph comes form its says:

This graph shows an ergo-training for the FLUX Smart with a certain gear setting (39 tooth front chainring and a 19 tooth rear cassette). It illustrates the amount of wattage (power level) that the Tacx FLUX Smart can produce in the specified gear setting with a certain cadence.

So the gearing matters. I replaced the cassette on the trainer with the casette from my bike that has a bigger sprocket. Now I have 39 x 27 gearing. Did a quick test, the pedaling feels much easier and the wattage is much lower. Still a bit higher than what was asked but close enough.

So tomorrow I can start my training program. :smile: