GRX-810 Power meter accuracy?

It has been over a year now that 4iiii have PM’s for the GRX crank. Knowing what we know about the inaccuracies of RIGHT side Shimano based PM’s, can anyone speak to the accuracy of the GRX RIGHT side?
The design is very different to the road cranks in that it’s symmetrical. Anyone wish to speculate? Or relate experience?
(EDIT: Stages have no right side PM for GRX only 4iiii at the moment)

Do Stages do a dual GRX crankset?

They do not actually. Only left side. Sorry for the error in my original post. 4iiii does however do a dual, and have done so for over a year. Thats the one I am personally looking at (being in canada)

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Indeed, the RX-810 crank looks symmetrical from the pictures, and at least theoretically, many of the forces should act (more) symmetrically on the power meter’s strain gauge. But AFAIK none of the people who matter have published tests and confirmed that. @GPLama at least would have mentioned if he had.

Given that, I’d probably opt for something else.

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I’ll try get a hold of one for a Lama Lab Test and a gravel spin or three.


A Lama lab test would be awesome!
My predicament is that a left side would not fit on my Trek Checkpoint so right side is kind of the only way to go. I just don’t want a 400$ power estimator…

I threw the question at a rep from 4iiii and this is what I got:

" As far as the Right Side inaccuracies are concerned.
4iiii Powermeters utilize 3D strain gauge technology to fully capture the power being applied to the crank arm. By measuring the strain directly, and not relying on algorithms, our technology is able to map more complex strain fields. Recent reviews have referenced challenges based on the current generation of asymmetric crank arms being produced by Shimano (R7000, R8000 and R9100). Our engineering team identified this in early stages of development of these cranks and used our 3D strain gauge technology together with an improved calibration process to maintain our high standard of 1% accuracy of our powermeters."

How do you guys feel about this?

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Without independent testing I wouldn’t make a purchasing decision based on that. I don’t envy 4iiii: it isn’t their fault.

Unfortunately, according to preliminary testing by @GPLama Shimano’s 12-speed cranks still give inaccurate power readings. The onus is on Shimano IMHO to prove they can make a reliable power meter.


I share that sentiment. They are up against a lot. I just dont love their staunch defence of the “1%”…
I will most likely get one anyway and cross my finger that @GPLama’s test will have positive results.

Probably a bit high on the budget but have you considered a Power2Max? They have a GRX drop in replacement

If money is no object, I’d go for a Quarq crankset or a Rotor crankset with a Rotor power meter. Rotor’s cranks are top notch, machined works of art that are modular.

Thanks for the input @jonesy and @OreoCookie. Those are great options for sure. The grx drop in option is especially appealing. The price however is prohibitive in my case.

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I know, your options kinda suck. If I were you, I’d go for a left-only power meter. In fact, in December I did for my new-to-me mountain bike. It is not as good as a two-sided power meter, yes, but it’ll work.

I was wondering this as well. The 4iii seems ideal but the inaccuracy of Shimano based right sided power meters puts me off. Here is to hoping @GPLama can get a sample and test it.

The power2max uses their own proprietary chainrings for GRX which put me off a bit. I don’t really want to rely on them for supply and I would prefer to keep the Shimano rings anyway. I emailed power2max and they said “At the moment we have a p2m that fits a GRX chainring (1x only). But that is certainly not the last word on the subject. That’s all I can say at the moment”

I took that as they are working on something that can drop in GRX 2x chainrings. They have something similar on the road side. But who knows!