Rotor have created rings that aren’t circular – they’re essentially oval. This, they say, maximises your power by effectively overgearing and undergearing in key positions of the pedal stroke.
When your leg is in the 2 o’clock position it has more leverage, so here the ring is bigger to take advantage. At the 5 o’clock position your legs are at the weakest point, so the rings become smaller, allowing you to spin more easily.
Biomechanically they do work, and while Q-ring claims only a 4.1 percent increase in power, the effect on pedalling is very noticeable; not so much at higher cadences, but on granny ring crawls the ‘drop’ in tooth size at the stroke’s dead spot allows a noticeably easy push to keep the pedals turning.
Fancy ring design aside, these CNC’d cranks cut a striking aesthetic against the more common smooth forms of carbon or forged alloy. They’re stiff for light alloy-axled cranks – something aided by big, BB30 bearings and BSA cups – but they’re very expensive too.
To be blunt, it’s a struggle to see what advantages that money is buying you. That said, the bottom bracket features high quality bearings, while an innovative normal-to-BB30 adapter allows you to get some of the performance advantages without having to buy a new frame.
Due to the egg-shapeness, front shifting isn’t as good as with regular round rings, though with the double we tested it’s easy to hold off shifting on the front. We also found that even with the upper and lower limits set on the front mech, it was easy to overshift the chain right off the rings.
Once we got used to using a slower shift the chain dropping problems were reduced, but it’s not ideal. We missed the dependable-under-pressure ability to almost crash-shift you get used to with regular rings.
Our set also randomly but constantly loosened off, to the point where the drive side almost fell out. Yes, we should’ve felt the play sooner, but we didn’t expect it, especially as we’d tightened the cranks to the massive required torque upon fitting.
The chainring bolts loosened rather quickly too, though that was nothing a dab of threadlock couldn’t fix.
These cleverly-shaped chainrings wear quickly too. We’ve ridden big miles on them, it’s true, but not so many we’d expect them to be wearing out already. We talked to other users of Rotor’s oval rings – both mountain bikers and roadies – and found early wear is relatively common. That’s not encouraging when replacements are so expensive (triple rings are £180, a double set £160).
The 3D+ idea is neat, but design problems, high price and rapid wear all hold it back.
This article was originally published in What Mountain Bike magazine, available on Apple Newsstand and Zinio.
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Edward C. Scates Donna E. Grace Juan S. Trudeau Daniel P. Turner Douglas R. Petersen
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