Absolute Black’s first ovalized chainring came out this summer and in a 32-tooth, 104BCD version. Now, he’s added a SRAM direct mount spiderless version with the same 32-tooth count.
Coming in at a claimed 59g, it’s only a few grams heavier than the round GXP or BB30 versions, and has the equivalent of a 30t profile in the dead zone and 34t in the power zone. The teeth use their proven narrow/wide profile, which we’ve had pretty good success with when used with a clutch rear derailleur (and even without one on a ‘cross bike). They’re available for preorder now in black, red or blue, and they deliver around October 20th.
Along with the pics, AB’s founder sent over a few pics and video to illustrate the chainrings in action and an explanation of why theirs are among the best out there…
He says it’s a misconception that oval rings let you produce more power. Rather, they just make you quicker “by clever distribution of your energy. They are very similar to Rotor rings in terms of shape and clocking of the power zone … this is simple mathematics of leverage.”
Rather than paraphrase, here’s Marcin’s full explanation:
“So with an oval ring, you push a ‘larger’ gear (greatest radius of the oval), only in the power part of your stroke (= cranks slightly below horizontal). Then your leg speed increases a bit through the rest of the stroke as if you were pushing a smaller gear. You do not require as much leverage to push the oval ring as you sweep through the bottom of your stroke. It’s simply amplifying the “pulsing” of a natural pedal stroke. No one pedals in perfect circles. But the thing which is most confusing to everyone is that you will actually feel that your stroke is more “round” with an oval shape than with a round chainring. This is something you can’t imagine and I can’t show on the website – you have to try it to believe it.
“In other words, it is easier to make the same power, as the pedal stroke is smoother and you feel stronger in the dead part of the stroke. It uses mechanical advantage (lever, really) to allow less exertion = reduced torque, but more constant speed (instead of pumping/mashing). Humans are not machines, so they do not generate constant power and speed across the whole revolution. An oval amplifies the power zone where humans can push harder and minimizes the dead zone since legs can’t create torque when the crank is vertical.”
And if you’re worried about their use affecting a clutch derailleur or chain tension on a singlespeed or fixed gear bike, here’s a video he sent us:
In other news, he’ll be adding a 34-tooth version of the oval 104BCD chainrings in mid-November, followed by a 32-tooth Cannondale Hollowgram direct mount (spiderless) oval chainring in late November.
