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Neo Trainer and fenix 6 watch are showing completely different speed/distance?

ca4623240a1f4c289d08ed5d245d188c
over 2 years ago

I paired my fenix 6 watch with my TACX Neo trainer. It is a direct drive trainer, so the rear wheel (along with the regular speed sensor) is not on the bike. Somehow, my watch is reporting 12 mph while the trainer app is reporting 17 mph at a given power that should be about 17 mph.  No matter how much I speed up on the bike or set a decline, the watch speed reads about the same while the trainer reading changes as it should.

If the watch is not getting speed information from the trainer, where is it getting this information from? I cannot find any way to calibrate the watch to the trainer. My watch is correctly reading power (from the trainer) and cadence (from my cadence sensor), so I'm not sure what else to try. 

  • 0 over 2 years ago

    On the watch you need to manually set the wheel circumference for the trainer speed sensor. Try 2133 for starters.

    But if your speed in the app is derived from your power output influenced by gradient, rider weight, surface drag etc then do not expect speed and distance to match between the watch and the app. They are measuring different things. The app shows your simulated speed for the various inputs. The watch just shows the flywheel rotation speed X virtual wheel circumference. In erg mode especially, or when descending in the virtual world, the gap could be vast. 

  • 0 over 2 years ago in reply to eezytiger

    Where do I set the wheel circumference? I don't see that as an option on the watch when I connect to the trainer.

    What is the point of having a Garmin trainer that connects to a Garmin watch if they don't record the same information?

  • 0 over 2 years ago in reply to ca4623240a1f4c289d08ed5d245d188c

    In the sensors menu on the watch select your speed sensor and then set the wheel circumference. The default of Auto is useless as there is no GPS available for wheel size auto calibration.

       

    As I already explained, the watch records the speed/distance from the trainer speed/distance sensor. You don't say what your app is, but I assume it uses power output from the trainer from which to calculate a simulated speed in its own little world. The watch doesn't see that simulated speed or the distance that results. There is no point in trying to make them match or expecting them to. The trainer does not experience elevation gain. The watch can only record a "flat" ride. If your app (e.g. Zwift) has hills, draft dynamics, surface drag changes, the watch can't possibly know about these things.

    In erg mode you might hold 250W for an hour. You might do that in a low gear with slow wheel speed or a high gear with fast wheel speed. The speed could be anything. In your app the speed of the flywheel does not matter. What matters is your power. If you are riding up Alpe do Zwift at 250W your simulated speed will be slow. If you are descending Alpe du Zwift at 250W your simulated speed will be crazy fast.

    The speed of the app is nothing to do with the speed of the trainer or the speed recorded by the watch. If you want everything to match up then record on a single device and sync the fit file between the platforms. Zwift will allow you to do that easily. No idea about other apps.