Before I begin I would like to make it clear that Osymetric chainrings are different from Rotor’s Q-rings or their new QXL-rings for that matter. One is Spanish and the other French. Rotor makes complete cranksets whereas Osymetric makes chainrings and pretty much nothing else.
Now you might say both chainrings are not round. That I would agree. Well, maybe more specifically, they are not circular. That is pretty much where the physical similarity ends. Osymetric chainrings are not elliptical as many presume them to be. Both Rotor and Osymetric set out with the same agenda – to eliminate dead spots in pedalling circular chainrings. That is because our legs are just biomechanically incapable of turning perfect circles. Both attempt to accelerate your feet through top dead centre (TDC) and bottom dead centre (BDC) by having a lower effective tooth count. For the 52T pictured below it is effectively a 56 at the power phase and a 48 at the dead spots.
Rotor Q rings have the same basis for their design. But the degree of ‘ovalization’ is much lesser. To be precise, Osymetric rings are not ovalized. Instead they are a ‘twin-cam’ design – two circular rings offset from each other and then joined by flat spots where your TDC and BDC are. Jean-Louis Talo, father of Osymetric, says that at the dead spots our legs have no strength. Hence the radius of the chainring needs to be drastically reduced to help us through that area. If we were to plot a curve illustrating the power generated at the power stroke vs the dead spot, the spike or dip in power would be rather drastic, not a gentle oval as the manufacturers of the Q-rings would like you to think it is. Even then, they have recently launched the QXL rings which have a more pronounced ovalization, it still does not come close to the benefit of having a flat spot to cancel out the dead spots in our pedal strokes.
That is not to say that Q-rings offer no benefit. James Cunnama, a professional triathlete, won 2 70.3 races on Q-rings after his standard rings got stuck in custom. He is now a Q-ring convert. But perhaps he was already stronger to start with? As we all know team Garmin-Sharp is sponsored by Rotor, but not all their riders opt for Q-rings. On the other hand, several pro tour riders have gone against the wishes of their sponsors and put blacked out Osymetric rings on their bikes. Sir Bradley Wiggins, Christopher Froome and David Millar are just a few of these riders. Frederick Van Lierde, last year’s Ironman World Champion is another long time Osymetric user. I personally have not ridden Q-rings. But my coach Shem rode them for a while before switching to Osymetric. The advice he gave me was to go the whole hog and give Q-rings a miss.
How does it ride?
Some of you may expect me to be bouncing up and down my seat, but I found the rings surprisingly natural. The adaptation I believe is one that is more psychological than physiological. The trick is to not think about the rings being weird and just pedal round circles like we normally would. Bear in mind that although the chainrings are not circular, your pedal stroke is. The chainrings do not alter the feel of your pedal stroke.
As you can see from the above picture they fit perfectly on the SRAM Red 22 crank. The new SRAM cranks use a new bolt arrangement. Fret not, it is still 5 bolt but they have moved one of the bolt attachments to just below the crankarm. As such the installation instructions that come with your Osymetric chainrings will not make sense. Just install the chainrings as pictured above, which is pretty much the opposite of the instructions, ie. the “52” and “130” goes opposite of the crankarm.
Why isn’t everyone using them?
If non-circular rings are that great, why aren’t all cyclists putting them on their bikes like Zipps? While innovation is mostly welcome, we are very reluctant to change. It does not help at all the Osymetric suffers from shifting issues. Shifting is best done only in the power phase else the front derailleur has little to push against. Earlier versions of the Osymetric chainrings lack shifting pins and ramps which exacerbate the shifting issues. Installation can be a pain too. Osymetric offers a video which makes the installation look like a breeze. If you opt for the 56T, it may not fit the upper limit of your derailleur braze. However with practice and a good mechanic, the loss in shifting performance can be minimized.
Cost is another issue, at over 300 bucks for a set, it is quite hard to justify forking out that kind of cash when you have to ditch your still working circular chainrings. And above all, it is just not cool. But then again, Adamo saddles were frowned upon not long ago.