Vintage bike on Tacx Vortex Smart

Hello dear Zwift fellows,

Here my setup:

  • Tacx Vortex Smart (year 2015) + Tacx donggle on HP Laptop (HDMI link to dumb TV)
  • Cadence sensor (Garmin)
  • Speed sensor on rear wheel (Garmin)
  • Vintage road bike (from 1980’, souvenir of my father) with Sachs Huet drivechain system : 3 chainrings and 6 speeds cassette (cogrings set) from 14 to 28 teeth

The setup works well in ERG mode.
However, in SIM mode, the pedalling hardness is starting to be not difficult enough (because I train quite a lot this year). In fact, I use only the 2 smallets cogs of the 2 biggest chainrings. Many times, I feel that I miss an extra smallest cog, for example 12 or even 10 teeth.


  • Is that necessary to use both a smart trainer and a speed sensor (on rear wheel)? Or my smart trainer is doing the full job by itself?
  • Is my problem linked to the fact that I use both a speed sensor and a smart trainer?
  • Shall I mount a different cassette with for instance a smaller cogring of 10 or 12 teeth?
  • Is there any other trick (Zwift parameters, …) to make the pedalling harder so I don’t have to modify my hardware?

Thanks a lot for your answers and experience :- )
Best regards, Sylvain

You don’t need the speed sensor if you’re pairing the trainer for power and resistance.

Does the bike actually have a cassette or is it a threaded freewheel? And given the Huret drivetrain, the other question is whether the rear hub has a French threaded freewheel, or a Maillard Helicomatic cassette - either of these would make it very difficult to change the gearing without replacing the wheel. If the frame has 126mm axle spacing and the hub has English freewheel threading, then you should be able to run a 7 speed freewheel, though it can be a little challenging to find freewheels with a smaller cog in 1st position (they do exist).

There are no Zwift settings that would increase the base resistance of the trainer. The other options would be to increase the size of the large chainring on the crankset (and probably also replace the chain with a longer one) or use the QZ app ( as a bridge between the trainer and Zwift in order to increase the base resistance level. If you want to know about QZ, talk to the developer, @Roberto_Viola


hi @Sylvain_Glatz QZ developer here, let me know if you have any questions!

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Thanks a lot Paul !