What's the consensus on oval chainrings?- Mtbr.com
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  1. #1
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    What's the consensus on oval chainrings?

    Are people liking these? How about swapping back and forth between bikes that do and don't have them? Road and cross would stay with normal rings but thinking about getting an oval MTB ring...

  2. #2
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    Properly shaped and phased, they work great. They reduce stress on the knees and allow more power. Also smoother at higher cadence.

  3. #3
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    My lap times and top speed has been faster since I installed my Absolute Black Oval.
    Salsa Carbon Bucksaw- Trek Farley 8

  4. #4
    NWS
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    Your other bikes will feel wrong when you switch back to a circular ring.

    I have three bikes, and put an oval ring on my slopestyle bike to start with. I switched back and forth a few times before getting an oval ring for my DH bike, because they didn't have 36t rings ready for a while. Oval is definitely better.

    I still don't have an oval on my AM bike, but it's the one I ride the least.

    The only problem I've had is that the 36t just barely touched the chainstay. I didn't notice until the end of the first ride... tick tick tick... what's that noise? A couple taps with an angle grinder fixed it.

  5. #5
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    Felt the same way after putting it on my main bike. It feels weird to be on a bike without oval, after getting used to it, and I don't plan on going exclusively oval, so I ditched it since there doesn't seem to be a significant enough gain and it costs more. That and I'm worried about my RD's clutch wearing out sooner. 34t managed to fit on my bike, but it has an odd spacer setup that seems to push the driveside crank out, due to the taco blade option or something.

  6. #6
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    Smoother distribution of torque, means no more spinning-out on steeper, techy climbs. Me likey....
    "This is a male-dominated forum... there will be lots of Testosterone sword-shaming here" ~ Kenfucius

  7. #7
    Trail Ninja
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    By "smoother distribution of torque", you mean it puts out less torque at the wheel when you're most likely to put out high torque on the cranks (downstroke), and more torque (at the wheel) in the dead zone, right?

    Just asking, since I can't prove it with math. Seems torque at the wheel is affected mainly by the crank length and the rear cog's radius (assuming fixed rider weight). Torque at the crank gets transferred to the rear cog as chain tension, and the bigger the cog's radius, the more wheel torque you get. 32t or 34t, with the same crank length letting your weight do all the work on the downstroke, you put out the same tension on the chain to drive the rear wheel, just that the crank just spins at a different speed. Based on this, the only benefit that I can expect is if it optimizes cadence-based efficiency. I kind of get the gist of it if I think about in it using abstract motor vehicle ideas, where a higher gear or lower RPM nets less torque and less torque results in less acceleration, and less chance of peel out, but I just really can't see how it works from a bicycle perspective.
    Last edited by Varaxis; 07-05-2015 at 02:40 AM.

  8. #8
    NWS
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    I don't think "torque" really adds clarity here.

    Your legs are effectively stronger when your knee is near full extension, and weaker when bent. If you have ever used a leg-press exercise machine you've probably noticed that you can lift more weight when you slide the seat back.

    The oval ring acts like a smaller chainring when your legs are at the top of the stroke, thus bent, thus at their least strong. And it acts like a larger chainring near the bottom of the stroke, when your legs are at their peak strength.

    The primary effect is a chainring size that effectively varies during the pedal stroke. That creates a lower gear ratios at the top of the stroke, and a higher ratio at the bottom. It feels very right, like it evens out the exertion of the pedal stroke from top to bottom.

  9. #9
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    "Your legs are effectively stronger when your knee is near full extension, and weaker when bent. If you have ever used a leg-press exercise machine you've probably noticed that you can lift more weight when you slide the seat back."
    - There's a paradox related to that statement, where a shorter crankarm lessens knee bending at the top to take advantage of that power output, but also creates less torque (average power output/wattage to speed ratio doesn't necessarily change; more people accepting crank length as a fit/feel choice now). Also, in the leg press machine example, you have a something solid to push against, while you only have your weight on the bike to push against (and your upper body strength, if you pull up on the bars as you push down on the cranks). All you're pointing out is that a larger muscle group is used for that part of the leg extension. Increasing the size of the chainring increases the resistance, but more reps with less resistance can be equal the same total power output, likely with less fatigue in the long run.

    "The oval ring acts like a smaller chainring when your legs are at the top of the stroke, thus bent, thus at their least strong. And it acts like a larger chainring near the bottom of the stroke, when your legs are at their peak strength."
    - Top of the stroke is bottom of the stroke for the other leg. They don't do a synchronous rowing motion. What it effectively does is slow down (adds resistance) the stroke when you're putting more power out and speed up (lessens resistance) the stroke when you're putting less power out.

    What it does is concentrate demands for power from the largest muscle groups, and ease demand from smaller lesser used and less efficient muscles. This is actually similar to the flat pedal vs clipless pedal argument. Studies have shown that flat pedals were no less efficient than clipless over a length of time, due to how the bigger muscle groups are the main ones powering the pedal stroke and how drawing more power from those smaller muscle groups is inefficient, but in a real life situation clipless wins the argument due to how the ability to draw a burst of power in a technical pinch was useful, on top of having a secure contact point. For those able to "spin a smooth circle", on demand for a surge of power, which type of ring would be better? For those that simply just mash harder, picking up and dropping their weight heavily into the pedals, which type of ring would be better? It's become that sort of argument in my eyes, with no clear answer and merely a preferential decision, like the wheel size debate and clipless vs flats debate.

    Oval has not yet been scientifically been proven to show significant gains in performance. In the books I have read that have supported this claim, the only real variable for efficient pedaling that truly shows a difference is cadence, and that's what gear selection should be focused towards optimizing. Oval vs round would need to be proven before I bother giving it too much consideration... I'd consider it as impactful on your ride as the width of your bars, length of stem, which pedals, which saddle, etc. which aren't totally insignificant, able to make a ride unpleasant or more pleasant according to what you're familiar with.


  10. #10
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    I love my oval. I use a Wolftooth and I want to try some others also.

    In the words of my friend who had never even heard of one, after test riding mine, "You don't even need to shift on the hills".

    While that's a bit of a stretch, it's definitely made climbing easier. I bought it on a leap of faith because of exactly what Varaxis said, "Oval has not yet been scientifically been proven to show significant gains in performance".

    It doesn't matter to me now. There's a definite advantage - and if it's all in my head - it's still helping.

  11. #11
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    Quote Originally Posted by dledinger View Post
    I love my oval. I use a Wolftooth and I want to try some others also.

    In the words of my friend who had never even heard of one, after test riding mine, "You don't even need to shift on the hills".

    While that's a bit of a stretch, it's definitely made climbing easier. I bought it on a leap of faith because of exactly what Varaxis said, "Oval has not yet been scientifically been proven to show significant gains in performance".

    It doesn't matter to me now. There's a definite advantage - and if it's all in my head - it's still helping.
    Exactly.....my butt dynamometer approves!
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  12. #12
    NWS
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    Top of the stroke is bottom of the stroke for the other leg.
    The major and minor axes of the ellipse are about 45 degrees off from the crank arm, so the ring is effectively largest shortly before one leg reaches the bottom and the ring is effectively smallest 90 degrees later as the other leg begins the power stroke.

    That's not what I expected to see when I opened the package - I expected the minor axis to be parallel to the crank arm - but having ridden Absolute Black's ovals for a while, I think they got it right.

    I agree that these rings probably do little (if anything) for the problems you see to be most interested in. I take no position on long-run fatigue or performance. Most of my exertion happens while coasting - hitting jumps and landing them - so I'm in no position to evaluate that sort of thing. I take no position on knee pain either. That was never an issue for me, before or after switching.

    But it works like a smaller ring when I'm switching from one leg to the other, and it works like a bigger ring when I'm putting down the most power. Both of those are desirable to me, and I have not found any drawbacks, so I'll be getting a third ring before the summer is out.
    Last edited by NWS; 07-05-2015 at 02:26 PM.

  13. #13
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    Liking the AB a lot, feels like it has cut my shifting in half, Will not go back!
    don't tell me, "Show Me " !

  14. #14
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    Any experience with Wolftooth and others? Need direct mount...

  15. #15
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    Mine is a Wolftooth, although a 104BCD. I own several WT products and they're all awesome. If I needed a direct mount and they made it, I wouldn't hesitate.

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