Fenix 7 11.28, Tacx Trainer Plus 4.0, Zwift, mileage seems wrong on watch and GC

Same here for Neo Smart Bike and Forerunner 245. Support just tells this is working as designed. Ridiculous...  I assume real simulation when entering all simulation coefficients (with some tolerance though).

With the Tacx app you can capture real distance. Watch tracking is useless...

Was thinking about a Fenix - no way when they do not fix this....

Tacx firmware 4.5 did not fix this issue.

Speed in Zwift is calculated based on your power output combined with gradient, surface type, bike and wheel choice, pack size and draft, weight and height. Then, of course, you have power ups and supertucks.

The trainer hasn't got a clue about these things. All it can measure is virtual wheel rotations to give a number for speed/distance.

Firstly you should set a wheel circumference in the watch so that it can convert rotations into distance/speed. But that is all kind of irrelevant when your wheel speed can bear little relationship to your Zwift speed.

For example, say you climb Alpe du Zwift at 100% trainer difficulty. Resistance will be extremely high, you'll pick a low gear and your wheel speed will be low on the trainer just as it will be in Zwift. But what if you reduce trainer difficulty - less resistance, faster wheel speed, same power output and same speed in Zwift as before. You can't expect wheel speed and zwift speed to match under these different conditions.

Now try climbing Alpe du Zwift in erg mode. Pick your power target and select any gear combination and cadence that suits. Speed up the Alpe will be Zwift speed, from power. Speed of the trainer wheel could be absolutely anything, depending on gear selection and cadence.

Now try descending Alpe du Zwift. You don't need to pedal at all, once you get going. Zwift speed - 80 kph. Wheel speed - probably something rather less, maybe even zero.

Firmware can't fix this. A fenix can't fix it. They are two completely disassociated measurements.

Note my experience comes from Neo 1 and Neo 2 trainers, I do not have a Neo bike, but the same arguments apply. And it's not just Zwift. It'll be any simulation software that generates sim speed from power instead of sim speed from wheel speed.

If you want your Zwift speed, distance and elevation in Garmin Connect then connect the accounts and have Zwift send its data to Garmin. But be aware that you may lose out on some of the more unique calculations within the Garmin ecosystem like body battery, recovery estimates etc..

Personally I dual record....

- Zwift to Strava for speed, distance, elevation, segments, social back patting etc.;

- Fenix to Garmin Connect for physiological training impact.

I don't give a flying fock about distance in Garmin Connect from Zwift. I know it's nonsense and it always will be. Outdoor rides - different story, but still irrelevant to me because I use Strava to track those as well.