Tacx Neo V1 speed waaaay off on zwift

I generally love the app, and hope someone knows of a fix for the below issue, as otherwise I’m going to have to retire from zwift, to prevent aggravating a knee issue that has already caused me to miss about 4 months of last year, which I need to avoid triggering again.

I use my Tacx Neo on zwift on an iPad mini over bluetooth, and I’ve noticed that when I ride at moderate speeds the speed of the ‘wheel’ and my virtual speed don’t match up (by the equivalent of about 4 sprockets), even on 100% realism. Basically I have to spin a much smaller gear, and have much less momentum than I would feel in real life. As an example, I checked some specific numbers this evening and realised that I was pushing around 85rpm in the 50x19/21 (i.e. around 27kph in the real world) to travel 40kph in zwift, so about a 1/3rd reduction in speed. This wouldn’t really be an issue (other than causing me to have to front shift/cross chain too often), except the virtual flywheel on the Neo also seems to reflect the ‘actual’ speed, so all of my riding on zwift is effectively a constant uphill slog without any momentum - even if I’m riding a flat route like the London Classic or Tempus Fugit. Because I have a knee issue, I really need to find a way of getting around this issue, or I’ll need to stop using zwift for training.

Is there a fix?

What is your trainer difficulty set at?

I’ve tried it at everything from 0% to 100%, the quoted speed was at 100% where it’s presumably supposed to be a direct copy of reality. Generally I ride around 50% so that I can feel the hills properly, but make it a little easier to hold a constant power. Talking of constant power, erg mode actually rides quite nicely, but that’s obviously not the point.

Not sure I understand that. Aren’t you saying you are seeing a speed increase on Zwift? Which is common, because there’s no head or cross wind. I could do > 30 km/h in the little ring in the flats on Zwift when I still had one. :man_shrugging:

Anyway, it’s probably best to send some log files (depends on your platform how to get them, search the forum) to Zwift support along with your own analysis.

FWIW, 1st gen NEO has been great and realistic for me for three years, especially uphill (admittedly I’m biased about what counts most, there :).

Good luck with your knee!

Cheers Eric, I’m hoping it heals up, but I need to be a bit more disciplined this year to avoid injuring it again.

The issue isn’t really the zwift speed, it’s the force it’s telling the trainer to apply for a given speed. The simulated speed is actually impressively close for the power and kit*. The issue is that there appears to be some speed scaling going on behind the scenes that makes the Neo run at 2/3rds speed (or 50% more resistance). So as an example:

  • 250w gives me 40kph in real life
  • In real life I’d probably be doing 95rpm in the 50x15 to maintain the speed
  • 250w in zwift gives me the same 40kph (more or less)
  • Doing this effort in zwift at 95rpm I need to use the 50x21, which would actually be like 32kph in real life
  • This wouldn’t be an issue, except the trainer treats the speed as 32kph with 250w resistance instead of 40kph with 250w resistance, which means that there’s not much momentum in the flywheel and it slows down quicker
  • This means the flat feels like a constant 1.5% uphill (based on plugging some quick numbers into aeroweenie), which would be fine for training, if it weren’t for my dodgy knee.

Turning down the realism decreases the resistance when climbing, but actually increases it for the faster stuff, so it actually makes it worse!

*I actually get less ‘bang-for-my-buck’ in terms of speed for a given wattage on the flat in zwift compared to real life speed, which is probably because as a track racer I ride 36cm bars in quite a stretched out and low position, and I haven’t unlocked the 404s I have in real life yet in zwift so have to ‘make do’ with a set of virtual Enve 3.4s.

I find this really interesting! I have a V1 Neo and love it and Zwift. It took my a while to get my head around the issue you have and I would agree entirely regarding the feel on the flat and even more so downhill! I felt it was just the way the trainer or Zwift worked and didn’t matter as it ended up as just a gearing issue for me. But given the knee injury, I can totally understand your frustration!
So the question remains, is it Zwift or the virtual flywheel on the NEO that gives the issue? If it’s the latter can it be improved with a software update?
Has anyone felt this and been able to compare between NEO and say Wahoo kickr, or between NEO and NEO 2T?