My frame won’t allow a chainring bigger than 34. There isn’t enough resistance on my fluid trainer for that small of a ring. 36 works, 38 is perfect. (Spider-based power meter.)
I sound like a hack, but, I can clear the frame if I mount the chainring on the outside of the PM. Chain-line is not good, but I’m never on the large cogs.
Any opinions on how or if this affects watt readings?
Thanks all.
For starters, you might want to mention the exact brand and model of PM involved.
Ignoring that, an email to that PM builder would be my real starting point. I am not sure any of us can say with any certainty what will happen. It might require A/B testing with a 2nd power source to have any real idea other than wild guesses.
PM is a Sigeyi AXO.
(Frame is a 2020 topfuel, trainer is an older Kinetic road machine.)
OK, just skimming the potential (without knowing the matching crankset), it might work ok. But we really don’t know if swapping the load path of the chain to the spider structure will still yield similar performance of the strain gauges. It very well could lead to errant data as the deflection might vary from what it was designed to do and how the device is calibrated to function from the factory. Again, wild guess, but I would hesitate to do it or trust the data.
Maybe you checked this already, but I see a potential for problems from the pure sense of having the chainring on the wrong side of the spider. Will the chain & chainring even clear the crank arm if you swap sides? It seems like there could be a collision between either or both of those that totally prevents it from even mounting and spinning.
(Crank is a xx1 dub/boost.)
Everything clears and shifts surprisingly well. I’d only us this set-up indoors. (30 tooth ring mounted correctly for outside rides) The reason I tried this, is I have a quark spider on a road bike that is a double. The strain gauges on that PM are obviously okay w/ the load being biased to either side. Thanks Chad.
I’m running into a similar problem. How did this workout?
I ran the ring on the outside for 3-4 months, it was fine. I’d only do it indoors, I wouldn’t want to accidently bash a rock w/ the ring like that. 
Thank you. I mounted mine yesterday (it’s a new power meter and my first spider) for a trainer ride and the power readings fluctuated a lot compared to my trainers power readings or my other 4iiii power meter that I have on my MTB.