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The Curious Case of Osymetric Chainrings

Alongside snails half-drowned in garlic butter and damsels with armpit hair, another once-off putting item from France that now makes my mouth water is the Osymetric chainring. It’s not oval-shaped or otherwise visually sensible. Rather, it has the profile of an egg with squared-off corners. Yes, it’s often mentioned in the same breath as Rotor Q-Rings or (God forbid) Biopace simply because it’s not round. But while trying them out here we’ve experienced something with pedaling efficiency that’s far beyond other chainring designs — round or otherwise.

Osymetric ChainringsIf you’re a data maven, we can steer you to science here. This humble What’s New article won’t get near the world of cosines and protractors. Instead, we’ll focus on first impressions –

The dead spot: Almost all of us have been riding round chainrings for so long we don’t feel the mythical ‘dead spot’ in our pedaling stroke. The chief benefit of Osymetric rings isn’t the elimination of something none of us feel. Rather, because of their pseudo-elliptical shape, Osymetric rings concentrate your pedaling power where your force is at a maximum, while effectively reducing the load where your power input is at a minimum. For example, a 52 tooth Osymetric chainring is designed to mimic as a 56 tooth conventional ring on the downstroke and then act like the equivalent of a 48 tooth at the very bottom of the stroke.

Ratios: Due to the variation in your effective chainring size throughout the pedal stroke, Osymetric rings don’t come in a 53/39 combo. Rather, the ‘standard’ ratio is 52/42 to optimize your pedaling forces. I’ve tested it in a variety of conditions from board flat criteriums to spirit-crushing climbfests. On both extremes (high and low) I never missed my 53 and 39. Early during my test of the rings, I struggled on one sustained 20 percent wall. Knowing I was in a 42 rather than my customary 39 may have led to a case of the yips on that climb. In retrospect, perhaps it shows that while there’s little conscious physical adaptation required (see ‘Thump thump’ below) after switching to Osymetric rings, they may require a period of mental adaptation.

Climbs: There is ample evidence of the use of Osymetric rings in the current professional peloton. Bradley Wiggins just won the Dauphiné using them. David Millar is a longtime Osymetric user, including his victory in the final TT of the 2011 Giro. Geraint Thomas is another fan. And Michael Barry has long championed them. In looking at their use in the peloton, the only inconsistency seems to come in the super-high mountains. For example, it appears Michael Barry went round on the Zoncolan stage of this year’s Giro. His reasons are a mystery to us — was it a cadence issue on monster climbs? Did he need a smaller ring?

Thump thump: In contemplating a test ride of Osymetric rings, everyone’s initial fear is the same: Won’t you feel a distinct ‘thump thump’ in each revolution as you turn over the ring’s acutest angles? The answer is an overwhelming ‘NO.’ Perhaps the greatest surprise of your maiden voyage is that Osymetric rings don’t seem to alter the feel of your pedal stroke. If you don’t look down, you’re not overwhelmed by the sensation you’re riding something non-round. There’s no ‘getting used to them.’ They feel natural from the start.

The downside: Setting up Osymetric rings is a bitch. They don’t cooperate with the spider of SRAM cranksets (I had to take my Force crank to a grinder). And they demand heavy-duty modification of your front derailleur. For example, I had to wedge the derailleur rearward at the braze on tab by 5mm, and I had to use spacers to widen the rear portion of the front derailleur cage. With a lot of preparation, you can make it so that Osymetric rings will shift fine. But the set-up is frustrating, and it’s almost impossible (at least with SRAM) to make it so that your chain doesn’t kiss the front derailleur with each revolution in at least some gears. However, we’ve been told that Shimano isn’t quite as problematic. While it isn’t plug-and-play, installation is purportedly a less difficult task with Shimano, and it purportedly shifts fine and works in silence.

Thomas CravenPRO is as PRO does: The mastermind behind Osymetric in the USA is Thomas Craven. Interestingly, he’s not importing the rings from France, but rather he’s licensing Osymetric technology and supporting the dying art of American manufacturing by having them produced in North Carolina. And while we give him props for having the vision to champion an enigmatic product, we also stand in awe of him for the fact that he raced for the 1990 7-Eleven Hoonved team. That is PRO.

Conclusion: Riding Osymetric chainrings is an experience like throwing on a set of Zipp 404′s. You don’t need an SRM to tell you something very good is happening. You’ll feel a tangible improvement in your ability to turn over a gear. It makes me question the long-term future of round rings, especially in an environment where the UCI blocks so many other innovations, often for arbitrary and inconsistent reasons.

The only hesitation I’d feel in recommending Osymetric rings — which is also the reason that, for now, we don’t sell them — is the lack of clear documentation (and a lack of experience on our part) for the initial set up process. Given the amount of jury-rigging and unusual fine-tuning of the front derailleur involved, it’s a recipe for frustration. This, of course, leads to product returns, something we like to avoid whenever possible. The brand is one exceptional installation manual (or well-produced Youtube video) away from being ready for the world. Or perhaps the answer is the invention of an Osymetric front derailleur compatible with their rings, as well as Shimano, SRAM, Campagnolo cranksets. That’s a tall order, but given the revolution they could create, it doesn’t seem too much to ask.