Oval, egg shaped chainrings aren’t new. Despite the failure of Shimano’s Biopace effort from the mid to late 80’s (the “clocked” or wider part of the ring was in the wrong spot and actually decreased pedaling efficiency) newer designs have seen success on the road, most recently in past years with wins in the Tour de France.
The concept is relatively new to the dirt, that’s because until the wide range acceptance of single ring drivetrains the design wasn’t able to provide consistent or reliable front shifting in off-road situations. That’s changed with narrow-wide teeth profiles and a small company out of the U.K. named absoluteBlack is leading the charge.
Manufactured in Poland, it’s beautifully CNC machined oval chainrings perform remarkably well, so good that I might be convinced to put them on all my mountain bikes.
Installation is easy, just bolt one on to a SRAM spider or choose the direct mount option. For bolts, the rings are threaded. For Shimano cranks, there’s a small arrow to line up with the crankarm to ensure proper clocking. Besides all manors of SRAM and Shimano compatible rings in common bolt patterns, absoluteBlack also makes ovals for Race Face and Cannondale Hollowgram direct mount. When changing over from round you don’t need to make any chain length or rear derailleur adjustments.
I set up a 32-tooth ring on a SRAM 1×11 drivetrain and within 10 minutes on the road riding to the trailhead I could no longer feel the elliptical design of the ring. That’s because the designer says the ring actually makes you pedal “more round” than a round ring by eliminating dead spots. Odd but it feels true.
The biggest convincer for me has been, of course, on the dirt. I’ve found that since converting I’ve been pedaling a gear or two higher on the cassette most everywhere when I’m pushing it hard, especially in technical terrain. This alone has improved my riding and whether I’m faster or not, I’m certainly smoother and that saves energy. I’ve also noticed better acceleration out of turns. At first I was concerned that using a bigger gear in the long run would lead to quicker fatigue but it hasn’t happened.
It’s been documented on the road that oval rings skew power meter readings and I don’t use Strava so I can’t quantify what I’m feeling with raw data, other than I’ve been having some really great days on the dirt since installing the ring. I won’t say it’s the Holy Grail of increased speed yet but so far I have no complaints or reason not to use one. It’s a beautifully crafted narrow/wide chainring, has never dropped a chain and just works great. Additionally, absoluteBlack has a 30-day guarantee stating that if you don’t like the ring you can get a full refund.
Look for a long-term test in Dirt Rag magazine next year.