Oval Chainrings

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Posted: Feb 20, 2016 at 4:18 Quote
This is some info for anyone curious about oval chainrings...
for anyone new to this idea...the goal of oval chainrings is to increase pedaling efficiency by minimizing the torque in the dead spots of your pedal stroke and maximizing them where you have the most leverage. In theory, it's a brilliant idea.

I will try to keep this short and informative. Happy to answer any questions.

Things you should know first:

- Most oval rings are different (each company with their own angles and oval shapes/extremities, often due to opinions or patents)

- Chain-line length throughout the pedal stroke does NOT change! Meaning: no, your derailleur will not be changing tension/moving as you are pedaling. Meaning....

- You can use an oval chainring on a single-speed setup without a tensioner.

- Today's oval rings are very different from the oval rings of 10+ years ago! Old ones basically had the idea backwards

- It makes more sense in a single ring/1x setup. Front derailleurs + oval rings can make shifting awkward. With today's trend of clutched rear derailleurs and 1x setups becoming more common...it's an easy transition for a lot of people, which might be why you're hearing about it these days.
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So here's my quick review and thoughts on my oval chainrings;
I bought 2, both from Absolute Black for my GXP sram cranks. A 30t for my town/city bike (29'er) and a 32t for my enduro bike (27.5).

Yes, I definitely feel the difference. It creates this sort of "stair stepper" sensation you should notice if you ride your bike a lot. However, it went away after a couple of minutes (literally) and I can't feel it anymore. So don't let that off put you! It's just a way of telling you "I can feel what it's doing." The average person who doesn't ride bikes often probably can't tell the difference. Side by side, they might though. It's subtle, but us avid mountain bikers will most likely notice this.

The goal of these rings might not be what you think. The way I like to understand it is as follows; The ovalation for a 32t ring means that in your dead spots, it pedals with the leverage of a 30t and in the strong spots, a 34t. That exact number is a little give or take as some companies might have less ovalation and others more. But that's the basic idea and I believe my Absolute Black chainring is just like that. So in that dead zone where it's pedaling like a 30t, it means that it would be pedaling a little faster and easier, meaning that I will pedal out of my dead zone more quickly and get to the sweet spot of my pedal stroke sooner. THAT MAKES A LOT OF SENSE!!

What oval rings do is often explained in awkward ways. The reason it's clever is; you out of the dead spots and into the sweet spots sooner! I've heard of the benefits talked about in many ways but that's the way I like to explain it.

That being said...I'm sure you understand, now, that different companies have different opinions on where exactly the dead and sweet spots are. Most of that's just patents, claiming rights to a certain angle/ovalation. I went with Absolute Black because they explicitly say that they were the first and did the most thorough research into their rings and everyone else is kind of ripping off of their discovery, taking their rings and changing things to avoid any copyright violations. But you can decide for yourself. There are a few companies doing this. (Absolute Black, Wolftooth, OneUp, Origin8, B-labs)

Try it! I love it both on my city bike and my mountain bike. I was wondering if it would make sense on both bikes. It does. But I'm thinking about switching the rings on my bikes, putting the 32t on my commuter/city bike and the 30t on my enduro. Why? I'll get into right below...

And since you've come this far, I'll tell you a couple more things you might want to consider

- Clearance from chainring to ground is closer to ground in standing position. So an oval 32t will be slightly closer to the ground than a round one is, but only slightly so. In other words, a 32t oval will have similar clearance than a 34t round chainring would.

- Since pedaling leverage is increased in the sweet spot, most companies advocate buying the same size chainring you have now. I suggest buying a size down, since your sweet spot will pedal with the same leverage AND have the same clearance. They just like the idea of you "gaining a gear" but I am happy enough knowing I can get out of my dead zone more quickly and still have the same clearance.

- They actually don't look stupid or off putting

- Ovulation jokes are still funny!!
(this is the chainring I got) Whatever your setup it, it should be available, from direct mount varieties to 94 or 104 bcd, etc.
http://absoluteblack.cc/images/_katalog/12/sram_oval_gxp_chainring_2.jpg

Posted: Feb 20, 2016 at 5:22 Quote
Thanks a lot! Just ordered 32t AB chainring for my 27.5 enduro bike an was looking for some additional info as well.

The main idea was to have a regular 32 ring for pedaling and 30t performance during uphills at the same time. I also have a chainguide with 34t capacity so that wouldn't be an issue.

Posted: Feb 20, 2016 at 6:00 Quote
^nice. Yes you get a lot of the 30t benefits right when you want them most and 32t in the strong parts to get the most distance out of the sweet spot. It's really cool.

Good thing you had a 34t guide!

Posted: Feb 20, 2016 at 7:31 Quote
So I run a 30t round now, would I want a 30t or a 32t oval?

Posted: Feb 20, 2016 at 23:33 Quote
nj82tj wrote:
So I run a 30t round now, would I want a 30t or a 32t oval?

I'd suggest a 30t if you've been considering going up to a 32, because it'll pedal like a 32 where you want it to. If you really like 30t, maybe think about 28t, as it will pedal like a 30t in its sweet spot

Posted: Feb 21, 2016 at 0:45 Quote
Went from a 34t round to a 32t oval AB chainring and I am loving it so far! Would definitely recommend getting one.

Posted: Feb 21, 2016 at 18:04 Quote
Just went from a 30t round to a 32t oval from oneup. Really felt the difference climbing, everything felt much smoother, definitely impressed.

Posted: Feb 23, 2016 at 7:50 Quote
How does it work with a top guide?

You set the guide for the longest radius in the oval?

Are you more likely to drop chains when the shortest radius of the oval is passing through the guide?

Posted: Feb 23, 2016 at 14:22 Quote
Back in the day late 80's early 90's when Shimano Biopace rings were all the rage people started to get lots of knee problems (I was a club road rider back then and had Biopace rings) and they quickly dropped right off the radar mid 90's - until now. So these modern rings from description sound the same as Biopace, they acted like a bigger gear mid power, lower gear out of powerful part of pedal stroke. So is it a case of people forgetting the downsides?


https://en.m.wikipedia.org/wiki/Biopace

Posted: Feb 23, 2016 at 14:41 Quote
Biopace and these are not even the same solar system let alone league.

Posted: Feb 23, 2016 at 19:14 Quote
StevieJB wrote:
Back in the day late 80's early 90's when Shimano Biopace rings were all the rage people started to get lots of knee problems (I was a club road rider back then and had Biopace rings) and they quickly dropped right off the radar mid 90's - until now. So these modern rings from description sound the same as Biopace, they acted like a bigger gear mid power, lower gear out of powerful part of pedal stroke. So is it a case of people forgetting the downsides?


https://en.m.wikipedia.org/wiki/Biopace

In my post, I quickly stated how they had the idea backwards then. This is what it should've been.

Posted: Feb 23, 2016 at 19:18 Quote
half-man-half-scab wrote:
How does it work with a top guide?

You set the guide for the longest radius in the oval?

Are you more likely to drop chains when the shortest radius of the oval is passing through the guide?

It'll work but yes you'd have to set for biggest.

If you have a clutched rear derailleur, though, and a narrow wide ring, it's safe to bet your chain won't flinch even without a guide.

But having one won't hurt. I can't say about the guide from personal experience. Ever since I went clutched I haven't needed one. However, a bash guard might still be nice

Posted: Feb 23, 2016 at 21:20 Quote
half-man-half-scab wrote:
How does it work with a top guide?

You set the guide for the longest radius in the oval?

Are you more likely to drop chains when the shortest radius of the oval is passing through the guide?

I use a top guide with my oneup oval. I have the guide set for the shortest radius of the oval, it has enough clearance to cover the shortest to the longest.

Posted: Feb 24, 2016 at 1:09 Quote
Bio pace wasn't the only oval ring back then Speedplay I think also had one reverse to Biopace and everyone at the time said that was even worse. I'm just sceptical because over the years loads of people have released non round rings and they have never taken off or stayed popular.

http://www.sheldonbrown.com/biopace.html

Edited to add the sheldon link, yep Biopace released as people found the opposite that came before even worse. Interesting Sheldon says Biopace are good for knees, never heard that before. Just goes to show how opinions on what's 'right' vary.

Posted: Feb 24, 2016 at 1:44 Quote
StevieJB wrote:
Bio pace wasn't the only oval ring back then Speedplay I think also had one reverse to Biopace and everyone at the time said that was even worse. I'm just sceptical because over the years loads of people have released non round rings and they have never taken off or stayed popular.

http://www.sheldonbrown.com/biopace.html

Edited to add the sheldon link, yep Biopace released as people found the opposite that came before even worse. Interesting Sheldon says Biopace are good for knees, never heard that before. Just goes to show how opinions on what's 'right' vary.

Well, have you tried it for yourself? Because everyone here with positive things to say seems to have.

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