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by Matt Wikstrom
May 2, 2016
Photography by Matt Wikstrom
Riders that have been involved in the sport for 10 or more years are likely to roll their eyes at the suggestion of oval chainrings. Different versions of the idea have been presented to the market on a multitude of occasions, but none have ever achieved mainstream use.
The argument goes that round chainrings have a dead spot that robs the system of some of its efficiency. Non-round chainrings are designed to eliminate this dead spot with the promise of modest improvements in efficiency for the rider. Sports scientists have been formally testing a variety of non-circular designs since at least 1992, yet none have reported any significant improvements over circular chainrings (though a few have reported mild improvements, such as that seen for non-cyclists using Osymetric chainrings).
Nevertheless, the idea has persisted, and currently, is displaying some resurgence thanks to the interest of MTBers. Absolute Black is one of a few companies supporting renewed interest in the concept with a large range of oval chainrings for MTB, CX, gravel, and most recently, road use.
Over the last few years, Absolute Black has been refining their design for an oval chainring, discovering that the optimal shape varies with the size of the chainring. The details are protected by a patent application, but according to their website, each chainring size has distinct timing and ovality. Importantly, their design is quite distinct from Osymetric chainrings that CyclingTips looked at a few years ago.
Absolute Black claim that their oval chainrings will provide “smoother pedalling action, enhanced climbing ability with less effort, and an overall increase in the enjoyment of the ride as a whole,” especially for recreational and sportif riders. They also believe that their oval chainrings will help “reduce or remove knee pain often experienced when riding on the road with round chainrings.”
At present, Absolute Black’s has created oval road chainrings to suit Shimano’s current four-arm 2x cranks (110bcd), any compact five-arm 2x cranks (except Campagnolo), and SRAM’s Direct Mount system for 1x cranksets. Buyers have a choice of 34/36/50/52T for 2x cranks and 50T for SRAM 1x cranks. All chainrings are available in black with extra colours (grey and red) for the outer chainrings (i.e. 50 and 52T for 2x cranks).
For this review, I spent all of my time comparing Absolute Black’s 36T oval road ring with a standard 36T chainring on a variety of climbs (0.5-4km) with gradients ranging 2.6-9.8%. Because it wasn’t possible to fit both chainrings to my cranks at the same time, I swapped one for the other every few days, covering the same terrain to compare how they performed.
I’ve been riding round rings for nearly 40 years so my first impressions of the oval rings weren’t favourable. I hated the way my feet seemed to speed up during each pedal stroke, suddenly accelerating with the small radius then returning to a normal speed with the larger radius. At high cadences (>80rpm), I felt like I was wasting effort with a choppy pedal stroke.
It didn’t take long for me to get accustomed to the oval ring though. After a few longer climbs, I stopped noticing the oscillation in foot speed and discovered an apparent increase in torque. It was most obvious on steeper gradients with higher gears and a slower cadence where it seemed easier to push through the dead spot to keep the cranks turning over.
However, I couldn’t find any evidence that Absolute Black’s oval ring actually affected my pedal stroke despite the strong impression it left on my legs. According to the data collected by Verve’s Infocranks, my torque effectiveness and pedal smoothness were identical for the two chainrings on any given climb. That my power output and cadence were also evenly matched argued that the oval ring was no better — or worse — than a round ring.
Of course, this is far from a rigorous study but I’m satisfied with the results. After all, they mirror the results for other non-circular chainrings, and while they challenge the veracity of Absolute Black’s claims, I have no quarrel with the product. However, I’d like to see them qualify all of their claims regarding the benefits of oval chainrings.
There is one certainty though: Absolute Black’s oval chainrings change the way each pedal stroke feels. I expect that some riders — especially novices — will enjoy the difference, while others will be frustrated by it. Ultimately, the appeal of oval chainrings is best left to personal preference.
For more information, visit Absolute Black and their Australian distributor, SCV Imports.
RRP: 34/36T, AU$108/US$62; 50/52T, AU$TBA/US$124; 50T SRAM 1x, AU$239/US$165.