Absolute Black's 30-tooth round direct-mount chainring for SRAM GXP cranks next to its 32-tooth oval chainring for 104 BCD cranks. Reportedly, pushing two extra teeth on the oval ring requires a similar effort as the smaller, round sprocket.
|Setting up the Absolute Black oval chainring requires little more than lining up the pip on the sprocket with the crank arm to assure that the timing is correct. Because the same number of teeth are engaged at any point of the crank revolution, the ovalized sprocket will not affect chain length, or cause the rear derailleur's take-up arm to oscillate as the bike is pedaled. As a result, switching to an oval chainring with the same number of teeth will not require a chain adjustment. Absolute Black's oval ring is well constructed and beautifully finished, and it mounted up easily to a Shimano XTR crankset. The chain, although not new, was relatively fresh and ran silently on the sprocket from day one.|
Initial rides with the oval chainring did not produce the "aha" moment I was expecting. A lifetime of spinning round chainrings caused my legs some confusion as my feet felt as if they were speeding and slowing with every revolution. That sensation faded quickly, but there were a two more lessons to learn before I became completely adjusted to pedaling an asymmetrical sprocket. Saddle position fore and aft affects the timing of the sprocket and the legs. I discovered that sliding my saddle one centimeter forward made for smoother pedaling. I also learned that the oval ring favors a slightly lower RPM as well as a steadier cadence, so I found myself shifting more often to stay in the sweet spot.
Once sorted, the oval chairing's advantages were readily apparent. Pedaling torque was more consistent, which made it easier to maintain pace up while climbing. Controlling rear-wheel traction was made easier, presumably, because I was getting through the "dead zone" with greater ease, and that allowed me to top some technical steeps that I often struggled with. The slight pulsing sensation could be a distraction on the flats, where minimal pressure was required on the pedals. The pulsing disappears if the rider chooses a taller gear and a slower cadence, or when the terrain asks for more leg power. The bottom line for Absolute Black's oval chairing is that switching to one is a sure way to ease up punchy technical climbs, and it could also be used to widen the gearing ranges of one-by drivetrains by allowing the rider to push two more teeth up front without sacrificing the bike's climbing ability. - RC
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