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Does the 165mm arm read less?
My understanding is that you need a slightly higher cadence for the same power/speed on a shorter crank, so with a matched cadence, the Stages might read more?
Also as the Quarq assumes the upstroke to approximate the power in the left crank, the fact that this is a longer length might cause some calculation inaccuracy.
Acliff-
You are correct, on a short test there was an approx 17% difference with the Quarq reading consistently lower. LR Balance was close too. Smoothing out the data to 10s averaging, the difference is pretty big, e.g. 267w/301w at the top and 81w/110w at the low end.
I'm just trying to help my other half understand if she has an underlying illness that's coincided with swapping to the Quarq,if the readings are now much lower on it, or a bit of both. I'm not a doctor so I can only help with the PM stuff - I think the Quarq is working OK, presuming the longer left arm may have reduced the numbers and she will just need to do a fresh RAMP test when feeling better.
spinnnout
An odd question... would putting a longer crank arm on a PM impact the power reading?
Scenario: strapped a 170mm Stages Left arm to a Quarq Dzero crank with a 165mm arm. The difference between the two readings was substantial. Could this have influenced the Quarqs reading?