absolute-black-oval-SRAM-spiderless-32t-chainring

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…

absolute-black-oval-SRAM-spiderless-32t-chainring

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.”

absolute-black-oval-chainring-power-zone
The “power zone”, where your legs have the most leverage over the crank arm.

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.”

absolute-black-oval-chainring-dead-zone
The “dead zone”, where your legs have the least leverage over the crank arm.

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:

absolute-black-oval-104BCD-chainring

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.

AbsoluteBlack.cc

26 COMMENTS

  1. Wonder how different these are from the old biopace rings? Remember having those but not really liking them. Concept sounds good. The next big thing or the next big yawn, we’ll see.

  2. I’m wondering how significant the difference really is, if for no other reason than: logic would dictate you’re going to be pulling against the RD clutch in the 34t sections, as it will have pulled any extra slack out during the 30t sections. Is the difference significant enough to be worth that extra energy? I’m skeptical.

  3. Plus one for the green!!

    Also, Trainwreck – you can use the standard rotor oval chainrings on a singlespeed setup – it doesnt create enough slack to be a problem. Tried and approved!

  4. “you will actually feel that your stroke is more “round” with an oval shape than with a round chainring”

    Being an Osymetric user for now two years, I must say this is absolutely true. You really feel it.

    I don’t know about these chainrings but what I can tell is that at least with Osymetric rings you can be amazingly faster on the climbs and these asymmetric rings give you a significant advantage when going over obstacles.

  5. @Bob: These are more or less the exact opposite of Biopace. Biopace placed the portion with the largest radius when your pedal was at top dead center while current oval chainrings will put the portion of the ring with the largest radius when your pedal is in the highest torque portion of your pedal stroke.

    The intent of Biopace was that when your pedal was at top dead center, it moves the slowest, so they gave that portion the largest radius to try and even out your power output. It didn’t work so well. The new ones are much better.

    @groghunter: The chain engages pretty close to half the ring at all times which means that the RD cage won’t move too much. People can run oval rings on track bikes.

  6. Chainrings don’t determine whether your “stroke” is round, the crank does. Pedal strokes are round always, they can’t be anything else.

    The pedal stroke is no longer of constant angular velocity. Contrary to what the article says, the variance is greater (because it it is now non-zero).

    Marcin says: “it is easier to make the same power, …less exertion … but more constant speed…”. None of these things are true. There is more exertion to move the pedal through the dead zone because the pedal must move faster, there is more variation in speed, and it cannot be easier since power is power.

    The duty cycle is increased with elliptical rings. That is not necessarily a good thing biomechanically.

    The maximum cadence may decrease with elliptical rings.

    Finally, these rings are not similar to Rotor rings in timing because rotor ring timing is adjustable.

    Marcin is a hack, not an engineer, and BikeRumor just parrots what marketing people tell them.

  7. I remember *not* disliking biopace, but not really being able to give a flying eff about it, either. These rings might make a small difference in smoothness, but nothing *significant* like dude is claiming. An old and crusty frame builder friend once told me there wasn’t a huge difference between any custom bikes, but the customers wanted to feel the difference, so they did. I get the feeling that it’s the same thing happening with the rings? Improvement over round? Yes, probably. Significant? Not a damn chance.

  8. @ craigsj: Did not even try asymmetric chainrings???

    Of course you can do nothing else than pedal round because the pedalling movement is just spinning around the BB. But stating that by no mean invalidates the theory behind oval rings.

    What you seem to fail to understand is that it eases going trough the dead spot while adding radius where your leg is strong. It is all about optimization of a revolution to better match the effective power output of your legs around these 360° (which of course is all but a constant value)…

  9. @Derek while the chain engages half the ring at a time, you’re going to change the distance between the the derailleur cage & the leading edge of the ring as it cycles. all a derailleur spring/clutch does is take up slack in that distance. If that distance changes, the amount of chain that needs to be taken up changes. Track bikes aren’t spring tensioned, & therefore will have chain slop, it’s an inherent flaw in chain systems that don’t have an active tensioner. I’ve had rings that were poorly centered on a 104BCD cause binding on a SS, if these literally have so little change that they don’t cause binding on properly tensioned track bike, then I’m even more skeptical that the advantage is strong enough to balance out as a positive WRT the increased effort to move the chain clutch, even in if you’re only having to move the cage forward ~1mm.

  10. @gerald t. i bet you can make a narrow wide for a half link chain. just nobody has done it. the cut out just needs to be every other tooth to follow the profile of the chain. think about it. of course my post was all sarcasm so if you prove me wrong it’s all in good fun!

  11. I did ride the q ring set on my old 3×9 Mtb. The performance boost especially in climbing is significant! If you ride the wrong gear, or if your buddy in front of you forces you to slow down in a climb, you can keep going in stead of having to walk. With normal rings the dead spot in the rotation means you can not rotate below certain speeds because you can not apply the power to your pedals. Because the boost at the bigger part of the ring and after that the increase of rotation speed, you can overcome the dead spot and keep riding.

    For the rest of biking you hardly notice the difference. Perhaps a little higher rpm then normal.

    Hope you understand my mediocre English!
    Keep riding.

  12. Hey all, just had my first ride on the oval 32T 104BCD on my Specialized Epic WC 1×11.
    Pedal stroke felt a little ‘woozy’ at first but I soon got used to it. At high speeds it can still feel unusual.
    Verdict: I love the overall smoothness and feeling of power you gain. I felt myself running a lower cadence than usual and powering up over stuff. On switch steep uphill switchbacks I was a little less concerned that I would stall out – easier to keep the cranks going.
    I am pretty convinced this is a more comfortable, smoother way to pedal. I will keep testing them, maybe a few longer rides before deciding to use them in an upcoming 8-hour race.

    NOTE: I assumed that the ring bolts from my specialized crank would work with the AB ring. They don’t, you need to order the matching set of bolts from AB and you will only end up using the male bolt as the ring incorporates the female threaded part.

What do you think?