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@Scilly.Suffolk
Got some of these bundled with cranks I've just bought, so I might as well try them out.
What I'm unclear on is how best to position them.
Sheldon Brown wrote that the advantage of Biopace over previous non-circular rings, was that they reduced stress on the knees by having "...the small radius engaged when the cranks are horizontal, the large when they are vertical... ...Since the rider doesn't push as hard during the power phase of the stroke, and motion is slower when the leg is changing direction, the Biopace design is gentler on the knees than even round chainwheels."
However, Rotor also claim to reduce stress on the knees doing the opposite "Q-Rings change the equivalent tooth size by decreasing it before the dead-spots and increasing it when the rider is in the power mode...", resulting in "...Mitigation of knee pains: Since Q-Rings imitate a circular (but smaller) chainring around the dead spots, minimize muscle requirements at the dead- spots, just when your knees need it."
I'd appreciate that there will be a certain amount of trial & error, but I'd rather start in the ballpark as my left knee is still recovering.