I've been a Power Tap SL+ user for the last two years and its been very reliable, and pretty accurate and consistent in the power values. I went to the Quarq since I have some other wheels that dont have a Power Tap, thus the Quarq was the way to go. My concern is the wide range of offset values I see on my unit and others. What is the definitive anwer from Quarq regarding these values and the delta in power numbers a user will or may experience. I did a fari amount of research so made the leap to the Quarq. I assume the cranks come new from the factory in the box torqued at 10Nm and no need to adjust?

I did a 4hr ride yesterday in temperatures from 29-34 degrees. I did a manual calibrate at the start of the ride, and each hour after that just to see what numbers would be. I would stop each hour, unclip from pedals and calibrate. During the ride I would also randomly back pedal 4-6 revolutions.

Here they are for the ride. -316, - 312, -314, -312. So, only four points shift which is good. My question is what if my numbers were lets say +25, +22, +25, +21. That is only a four point shift also, but are numbers in the +20's better than numbers in the -300's? Or, does it not matter what the numbers are as long as you are in the -500 to +550 range and no more than the 50 point window for a ride?

Benlane, (I meant 40 points, not 50) thanks for my confirmation what I expected. BTW, does Quarq monitor these forums and give known engineering answers?

It's always best to send an email rather than rely on Quarq picking up the question on here. I emailed them and got an answer within a few days. Turns out my battery lid had worked loose and now the figures I'm getting are within the suggested values.

Hi RM,

I've just had a very similar problem to yours. out on a cold damp ride, my power numbers went crazy. maunual calibration returned various numbers ranging from -1000 to -8000. Tried changing the battery when I got home but the offset numbers were still wild. They gradually settled back down to around -260 over the course of 24 hours. it's back with SRAM in the UK at the moment who can't seem to find a problem with it but fortunately the retailer has persuaded them to just swap it out. on the negative side i've been without it for about 3 weeks now and have got to wait another couple before they can get me a replacement.

I am experiencing a similar issue. My Cinqo was working fine, the offset resting some where in the +500-550 range and was recently servived. After a rainy ride this past weekend followed by a bike wash the offset went crazy first it was +1200 then it was - 1200-1400 reading 0 watts when i pedaling hard. This morning I took another reading and its -321. Frustrating as hell because I was about to do a carefully timed fitness test and will have to see if ai can borrow a power meter. At least Quarq has great customer service I just wish the dang thing would go nuts during base training when I don't really need it.

I'm experience similar problems (0 watts, very high offset) the day before a 70.3 race. Frustrating since I use power to estimate TSS for the race. I've sent an email to customer service and I'm sure I'll hear back, however, it looks like there is no solution in such a short time.