Interesting. I replaced my 130 - 53 version and have a noticeable waviness as you describe for both of the used (worn out by a previous owner, bought a used SRM) and new ring. As i remember my deviation is 1-2mm.

Might be a problem with the manufacture.

I'll try to measure my old ring for flatness.

Thanks for your reply. So it seems not to be an isolated thing.

Residual stresses and machining distortion are always a problem with thin walled parts. Doing things properly takes a bit of effort, or you can just freestyle it and hope nobody notices...

After the seller told me that Rotor chainrings have a tolerance of 0.8mm (!) relative to flatness and to get stuffed, I just made my own. The chainring is a (perfectly flat) Sram Force 22.

That looks lovely. Good work.

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To be clear, your SRAM ring doesn't show the same waviness as the ROTOR ring?

Your ring looks pretty sharp, good work.

Thanks for the kind words guys. This is a bit of a rush job, I will do a complete cover, which also hides the central part of the power2max NG, for maximum aero-placebo-dynamic effect, when I have time to mill a mold.

Yes, the SRAM ring has no waviness at all (as other chainrings I have from Shimano, Praxis Works and AbsoluteBlack). I am quite unimpressed by the quality of Rotor chainrings. The small oval rings have absurdly sharp edges. This is a problem on an Ultegra 6800 crank for example, since you have to tighten the internal chainring bolt and the edges (from the multiple bolt position holes) are so sharp they will eat the bolt. Rotor chainrings are oval and have adjustable timing, that's about it.