Ich nutze einen Zwift Hub mit Cog der ersten Generation (Schwarz). In meinem Radcomputer (Sigma Rox 12.1) kann ich den Trainer in der Sensorsuche auswählen und verbinden.
Software-Versionen alle aktuell.
Mein Problem:
Die angezeigten Geschwindigkeiten sind leider um einen Faktor 3 bis 4 zu hoch. Entsprechend auch die gefahrene Strecken. Den üblichen Radumfang von ca. 2100 mm habe ich im Radcomputer auf 500 mm gestellt. Leider keine Veränderung. Was kann ich ändern, damit ich die richtigen Geschwindigkeiten und Strecken auf dem Radcomputer angezeigt bekomme? Vielen Dank für eure Tipps! 
If you are comparing speed in Zwift to speed on a cycling computer, they will never match because the cycling computer does not know about the terrain you are riding in Zwift.
Thanks, Paul. That’s right. But this is no my Problem . If it is nearly the right speed in a flat area it’s okay. Most interesting for me is the route in km not the speed in km/h.
I don’t think there is a solution to this when recording on a cycling computer. It’s normal.
Hi Paul,
my bike computer (Sigma Rox 12.1) is connected to the Zwift Hub via sensors (ANT+ or BLE, both possible). The data for cadence and power are transmitted without errors. Why not the route and the corresponding speed? Zwift shows me the correct values for distance and speed on the monitor. These just need to be transmitted? There are no other sensors outside of the Zwift Hub. Since the Zwift Hub works in direct drive, there is no wheel and therefore no additional speed sensor. Before that, the Rox gets values that are far too high (about four times as high)? My problem must therefore be in the area of the Zwift Hub => Rox 12.1 sensors. I have carried out a calibration. No change. I am at a loss!
The trainer doesn’t have that information so it can’t send it
So where do the values I see on the Zwift monitor come from?
Zwift reads the power from the trainer, and it has a physics model that takes that power number, plus your height, weight, which bike you are riding, the gradient you are on, the road surface you are on, how much draft you are getting from other riders, the effect of powerups, coffee stops, rubberbanding, etc. and it turns that into a speed number. The trainer doesn’t know the result of that calculation. Your question is a common one, but there is no answer other than do not try to compare the speed recorded on your cycling computer to the speed in Zwift.
Thank you very much for your detailed answer. I am also much less interested in the speed than the distance, because I combine it with the real outdoor rides in an app to calculate the annual mileage. That worked well for years. It must therefore be the Zwift Crog (virtual shifting with just one pinion) that is causing the rejections to be so severe. Up until then, the deviations were small and tolerable. Especially when the route had no or equally steep climbs and descents. Thank you again - even if there is unfortunately no solution to my problem. Manual accounting in an Excel table. 