I’m inclined to agree with the comments regarding the likelihood that a factory reset RUNN is more likely to be accurate compared to the actual treadmill, especially given that 12kph on the treadmill, as showing 13kph in Zwift via RUNN feels a lot more like 13kph outside.
I had a play with the Zwift calibration last night and realised it doesn’t do what I assumed (I assumed it would ignore the treadmill and calibrate RUNN to Zwift), it looks like what it will do though is calibrate Zwift to the TREADMILL speed via the input from the RUNN, which I do not want as that assumes the treadmill is correct (which it definitely is not).
What I was hoping it would do, which seems like it could easily be implemented? Is when you do the Zwift calibration, it should give you a real-time zwift speed on screen during calibration, so when it says run at 12.5kph for 40 seconds and you set your treadmill to 12.5kph zwift should be able to calculate, given the input from the RUNN, how “far” a zwifter should have ran in 40 seconds, then it can calibrate the RUNN to Zwift (and not to the treadmill), if that makes any sense at all?
Though I am yet to convince myself that’s even possible, as in theory I keep thinking you could self calibrate based on a pace bot, so if Zwift pace bot 11.9kph is on screen and you need to set your treadmill to 10.3kph to match the screen pace bot of 11.9 then you know that treadmill 10.3= zwift 11.9, but even then I’m not sure that’s a correct way of judging it as, lets say you have a faulty RUNN than reports speed 2x as fast as true, so if your belt is going 6ph and RUNN is sending 12kph to Zwift, you’d match the pace bot and therefore assume your running at 11.9/23 kph but your actually running 6kph.
Its doing my head in, If it was only 0.3-0.5kph different I’d be happy enough, but at over 1kph difference at 12kph I feel I really want to satisfy myself the RUNN is closer to real life than the TM.
Like Rober_C says, probably just have to do a belt measure & count to satisfy myself that the RUNN hasn’t gone skewy.