I have a garmin edge 500 w/ the latest firmware and also a Powertap Elite+ that was rebuilt last year with upgraded components and firmware. I'm not sure if it has the same G3 parts though. I was wondering if I should be doing a re-calibration through the garmin headunit during the middle of my ride. I am religious about doing a calibration before I start my ride but this is usually done inside my house before leaving. Sometimes there is a decent amount of change in temperature, especially during the fall and winter, from when I calibrate indoors to riding outdoors. Should I be doing a re-calibration through the garmin maybe 15 minutes into the ride? Or does it do this automatically while coasting?

Taking yesterdays ride as an example. I calibrated the powertap inside my home and got a 515 reading back. I went off on my ride and after about 45 minutes of riding, I noticed that my power looked a little low while riding up some hills. When I got to the top of the hill, I did a re-calibration and got back a 518 reading. After that, it looked like my readings were a little more consistent with what I was expecting.

Should we be doing more re-calibrations when we have changes in temperature? I don't think powertap's support auto-zero correct? In my example, was I probably outputting more power than what was displayed by my Garmin up until I did a re-calibration?