On another thread I saw that it is typical to have a mileage deficit on the Garmin when training on Zwift. I am using the “Bike Indoor” activity on the Garmin and it tracks most of the metrics but the mileage is shallow by about 18%. As a result, it is showing me the wrong average speed as well. Is there a way to sync this activity on the Garmin with the Zwift?
Not really. If the ride is perfectly flat, you might get close, maybe within 5% for 20 miles but that is as good as it gets IME.
Garmin doesn’t register the Zwift pace dynamics and drafting, it only registers the effort you are putting in from your trainer bike.
So naturally it will measure sometimes much less. Zwift speeds are way too fast.
FWIW, Zwift is rather generous with the speed/distance. Your Garmin is probably more accurate to real life riding.
I wonder if in theory there’d be a way that Zwift software could get say the laptop it’s running on, to broadcast a BT signal of the speed it’s calculating, that could be picked up by a head unit?