Flux S / Indoor Trainer on ERG Mode

Hi All, I have a flux S - i’ve had it about a year & did some training on it but never structured and not a huge amount of training at that…
Recently I started training consistently on TR… however, I have noticed that when pulling up to higher thresholds +290 watts… the trainer only seems to hold the power for a short time at a given cadence. In order to maintain the power output I seem to have to change gears otherwise I am spinning at 120+RPM to maintain the correct power to complete…
Is this an amateur error or a trainer issue? Or can someone provide guidance on how I can fix this… thks!

Have you calibrated the trainer and do you calibrate it often? If not, I would calibrate via either the TR software or the dedicated TACX app.

If that doesn’t resolve the issue, I would download the specific workout files and contact TACX (Garmin) directly. My Flux S started to have a similar issue and it was eventually replaced.

Thanks @PusherMan

I calibrate ever time before I train with the TR calibration so it rules that out.
Sounds like it might be a trainer issue… I was hoping it wasn’t this. I’ll try contacting Tacx… thks

Are you in a really low gear? I have a flux S and usually use it in a pretty low gear, and if I know the session is going to be 300+W for me then I usually go up a gear. I might be way off base here, but I think trainer’s have an upper and lower threshold for the amount of resistance they can apply to the flywheel so I don’t worry about it too much. I just try to be in the right gearing before the workout. If you’re in a higher gear and things aren’t stable, then I would go to Garmin.

On the big ring & in the middle cassette… I have to jump 2-3 gears to try and bring down the spinning.

Also I have noticed… I have to drop to the lowest gear on the back cassette to hit the suggested cadence between sets or threshold WO to try and get a smooth transition of power between the jumps… is this normal? thks

I certainly didn’t start changing gears, regardless of the session. I think that totally negates the purpose of ERG.

On my tacx vortex i have to change gears. In the mid 200s effort vs resting intervals… im on the big ring, and will do work at the middle of the cassette. When it’s a recovery interval (close to 100w) i have to shift down on the cassette otherwise i’m recovering “too high” and if i stay in that cassette gear for the interval then i have to spin a looooot

This sounds like you’re hitting the trainer ceiling.

If you’re in that hard a gear then that doesn’t sound right.

This sounds like your working above the trainer floor, which is common.

Kind of, but as above its very easy to hit the Wattage floor/ceiling if you’re not in compliant gearing.

I used to do this on my Tacx Smart, it didn’t have the range to accommodate big wattage jumps. I then moved to the Vortex and as yet haven’t had to change gears but I haven’t had any huge stomps yet :slight_smile:

On average what is the best gear to run on to avoid these issues? ta

This should explain things a bit: https://tacx.com/erg-training-flux/


That is a very good explanation!

That depends on you really, your typical cadence and your power needs. In some cases you may not be able to do the workout EXACTLY without the odd gear flick.

1 Like

Really good article thanks @PhydomiR

“With the FLUX Smart it is possible to perform these kind of workouts. This trainer can produce a certain range of power levels for a specific gear setting (illustrated by the blue shape in the graph below). In case your riding at the top of this range and you wish to increase the power or when it’s at the bottom of this range and you wish to lower the power, you have to shift gears.”

1 Like