I own several wheels with PowerTap G3 power meters. When I calibrate them successfully with my Garmin Edge 530 they give me some meaningless result number that’s something like 500-600 or vaguely in that range.
Recently I just bought a brand new wheelset with a new G3. For this one, whenever I calibrate it, returns a number that appears to range from -1 to -9. It seems random. I’ll get -3, then -5, then -8
But it says “Calibration Successful”. And when I switch to the normal display, it returns power numbers that look reasonable.
So is this some relatively recent change to G3 stuff? That they return negative numbers when you succeed?
Your readings sound about right and similar to what I get.
Mine are around the -6 mark and will vary slightly with temperature: colder goes out to about -12 when very cold and warmer temperatures go the other way.
I’ll typically do two or three calibrations, one after the other,but the readings only vary by 1 or 2 either way.
Coincidently my original G3 shit the bed recently and I sent it in for an overhaul. Just got the wheel back and installed yesterday. Very first calibration was -5 and I had the very same question.