The Tacx FLUX S was my first indoor trainer. I wanted easy pairing with Zwift or Garmin, a practical setup for my flat and a reasonable purchase price. In use, I learned that resistance is only part of the story: assembly, noise, storage and a stable connection matter just as much.
This review covers what worked, what annoyed me and why my initial satisfaction score of 65/100 was followed by a warranty replacement. These are my experiences with a particular unit, rather than a new test of every FLUX S available today.
The Polish original was published on 31 March 2020. This English version preserves the original experiences and later failure update. Historical prices are not current offers.
Tacx FLUX S video review
What was in my box, and what else did I need?
When I bought the trainer, I was new to bike tools. Cassettes, lockring tools and chain whips were not things I had thought much about. Opening the box quickly taught me that an Allen key alone would not get the whole setup ready.
My package contained the trainer body, base and an Allen key for attaching it. I also needed a cassette and the tools to fit it. This describes the package I bought; check what is included in the particular offer you are considering.
Fitting the cassette and mounting the bike
Assembling the trainer did not take long. A separate cassette compatible with my bike’s drivetrain made things much easier. Moving one cassette between the rear wheel and trainer before every session would soon become a chore.
With the FLUX S, I remove the rear wheel and mount the bike directly on the trainer. After a few attempts, fitting and removing the bike became straightforward. The learning process was not perfect: I once bent the quick-release skewer and had to replace it.
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What did the smart features offer?
For me, the main benefit was training with an app or a compatible Garmin device. The trainer sends ride data, while an app or bike computer can control resistance. The stable construction was welcome during rides, although its size became a drawback when storing it.
Zwift and the Tacx app
I tested connections with Zwift and the Tacx app. Pairing was easy, and I could see power, speed and cadence. Resistance changes let me feel the climbs. I did not, however, check power accuracy against an independent power meter.
Depending on the app, I could use prepared workouts, virtual routes and group rides. The FLUX S supports Bluetooth and ANT+ FE-C; check the available functions for the specific app and device you intend to use.
Training with a Garmin bike computer
I generally preferred workouts controlled by my bike computer to virtual riding. I could follow a planned session, control resistance and use routes. If you have a compatible bike computer, you do not have to choose Zwift just to train indoors.
Loading a race route was an appealing option. Still, the resistance-control problems described below showed that planning convenience does not guarantee every workout will run smoothly.
Everyday use: storage, moving the trainer and noise
Stable, but awkward to put away
The FLUX S was not something I could easily tuck into a corner after a ride. Its base bolts on, and the legs do not fold. Without a permanent training space, I moved it between the bedroom, kitchen and living room. At roughly 23 kg, with a projecting base, that became inconvenient.
A quiet trainer does not mean a silent setup
I found the trainer itself relatively quiet, particularly compared with a wheel-on trainer. The bike’s drivetrain and gear changes still made noise, though. In my flat, riding in the same room disturbed someone watching television. I have no decibel measurements; this is my experience of using it at home.
The complete setup costs more than the trainer
The original Polish review mentioned a price of around PLN 2,500. That is a historical figure, not today’s price or a recommendation of a particular offer. Old accessory and Zwift subscription prices have been removed because they could be misleading.
Depending on what you already own and how you want to train, I would include the following in the budget:
- a separate cassette compatible with the bike’s drivetrain,
- a cassette lockring tool and chain whip if fitting it yourself,
- a floor mat under the bike and trainer,
- a sweat guard and front-wheel support,
- a fan — I did not use one during the period described in the original review,
- an app subscription if choosing a paid option,
- a compatible bike computer if you want it to control workouts and do not already own one.
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Connection dropouts and resistance-control problems
The most annoying issue was brief connection loss. Speed or power data would disappear for a few seconds. It was short, but noticeable during training. A missing reading is not evidence of inaccurate power measurement; here I am describing a data-transmission problem.
Another issue appeared in workouts controlled by my Garmin Edge 820. After hard intervals, resistance suddenly increased and pedalling became much harder. This happened in two identical sessions. When I ran the same workout on my Fenix 6, I managed to complete it.
An attempt to calibrate through the Fenix 6 then produced the error shown in the photo. I did not establish the cause, and I do not assume that every FLUX S unit or current software version behaves the same way.
Garmin documents spindown calibration for the FLUX series through the Tacx Training app. See the Garmin calibration instructions for the procedure. This documentation is not proof that it resolved my historical issue.
Update after eighteen months: failure and warranty replacement
After roughly a year and a half, something in the trainer snapped. It began creaking badly, lost its ANT+ connection with the bike computer and stopped changing resistance during intervals. It was still under warranty, and I received a new unit after about two weeks.
This is an important part of the review, so it now has its own section rather than being buried in an update. I do not have failure-rate data for the product range or a long-term test result for the replacement unit.
Summary: was I happy with the Tacx FLUX S?
My initial satisfaction score was around 65/100. I appreciated the simple assembly, easy app pairing and ability to train at home. The size, repeated moving, connection interruptions and resistance issues were the drawbacks.
With a permanent training space, some daily inconveniences may matter less. For me, the dropouts and subsequent failure were significant. The warranty replacement helped, but it does not erase those experiences from my assessment.
Before buying, I would check more than the price: compatibility with the bike, the contents of the package and the opportunity to test pairing with the device I want to use. Technical details and manufacturer documentation follow on the second page.