Originally Posted by valygrl

I've been struggling with my G3 for a little over a year now. I have a SL+ on my aluminum wheel and a G3 on my Zipp 404. I do most of my riding on the SL+ wheel, and have found the SL+ readings to be stable, but the readings from the G3 were all over the map. Wheelbuilder (where I bought it) replaced the electronics unit for me last month, but it still is weird - it's more stable now, but my power numbers have been about 20-30% (PERCENT!!!!) low on this wheel compared to what I expect on my other unit. It's been tough to tease out if it's really a problem with the powertap or if it is because the circumstances i've used this wheel in are different - it's my TT wheel, and all my recent TT's have been at altitude, and they are flatter compared to some hill climb races I was comparing to.

I finally just sent it back to Wheelbuilder for recalibration yesterday. It will be interesting to see if there is a big change in the numbers after that. I tried to do the torque check test myself, but I had to borrow a garmin to do it with, and I'm not sure if I did the test right. It told me it wasn't mis-calibrated, but I still don't believe it.

FWIW, Wheelbuilder has been nothing but gracious and helpful with this thing, and it's been my own doing that it has taken so long to sort out - I didn't want to send it back without being sure it was wonky, but I was having a heck of a time picking apart the potential data issue from the sporadic and high-altitude usage.