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Non circular chain rings
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Hi,

I am considering getting a dual sided power meter. Either the new Rotor 2inpower or P1 pedals.
However, I would like to know if someone has any evidence that non circular chain rings help at all during long distance tri or if it's just an aesthetics thing.

Paulo

Paulo Matos
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Re: Non circular chain rings [pmatos] [ In reply to ]
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Re: Non circular chain rings [pmatos] [ In reply to ]
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I went thru this in the last month.
1) Worth trying. There is compelling mathematical simulation analysis that oval rings are better. But the support for the idea from the upper tier of cyclists is more mixed. For every top cyclist that likes them, you'll find one that tried them and then went back to circular. So worth trying, but not a silver bullet.

2) Lots of ways to do oval rings so you have to do some research in order to decide. I found a study that ran simulations and found that that the best solution a) didn't exist, and b) was too radical to work with a front derailleur.

3) Oval rings have compatibility problems with cranks, especially cranks that measure power. 110BCD seems a bit more problematic than 130BCD. Over the course of a month I prob called OEMs a couple dozen times asking if this or that were compatible. If you call them up you'll find that their chainrings or their crank is a lot more compatible with stuff then their published compatibility charts indicate. Obviously tho you'll bypass compatibility problems if you get a Rotor crank or you do power via pedals.

4) Oval rings don't hose up your power data. Altho few mfrs of power measuring systems officially state "compatible with oval chainrings" the general perception is that it's a non-issue.

5) Rotor sells some spacers to help you tilt your front derailleur. Worth getting.

I did end up getting oval rings on a Quarq crank, I've not ridden on the set up enough yet to draw conclusions. In a couple weeks, I'll be recovered from a month lost to race recovery and various failing body parts, and I'll be able to do a ftp test that should give me some feedback on this scheme. What I can tell you, at this point, is that it takes only a couple minutes to get used to them.

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Last edited by: RangerGress: Jul 12, 17 5:10
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Re: Non circular chain rings [Morelock] [ In reply to ]
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Morelock wrote:
here you go

Thanks. Unfortunately the final paragraph disappoints. :)

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Now then...on the question of whether or not non-round rings have the potential to actually increase pedaling power output...well, I have my opinions on that, but I'll leave that for another blog post....

Paulo Matos
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Re: Non circular chain rings [pmatos] [ In reply to ]
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You can message TomA (or he may see this thread)
I'm sure he can give you another blog post worth of info on it. But his post doesn't leave too much to expand upon.

My Blog - http://leegoocrap.blogspot.com
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Re: Non circular chain rings [RangerGress] [ In reply to ]
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RangerGress wrote:
I went thru this in the last month.
1) Worth trying. There is compelling mathematical simulation analysis that oval rings are better. But the support for the idea from the upper tier of cyclists is more mixed. For every top cyclist that likes them, you'll find one that tried them and then went back to circular. So worth trying, but not a silver bullet.

2) Lots of ways to do oval rings so you have to do some research in order to decide. I found a study that ran simulations and found that that the best solution a) didn't exist, and b) was too radical to work with a front derailleur.

3) Oval rings have compatibility problems with cranks, especially cranks that measure power. 110BCD seems a bit more problematic than 130BCD. Over the course of a month I prob called OEMs a couple dozen times asking if this or that were compatible. If you call them up you'll find that their chainrings or their crank is a lot more compatible with stuff then their published compatibility charts indicate. Obviously tho you'll bypass compatibility problems if you get a Rotor crank or you do power via pedals.

4) Oval rings don't hose up your power data. Altho few mfrs of power measuring systems officially state "compatible with oval chainrings" the general perception is that it's a non-issue.

5) Rotor sells some spacers to help you tilt your front derailleur. Worth getting.

I did end up getting oval rings on a Quarq crank, I've not ridden on the set up enough yet to draw conclusions. In a couple weeks, I'll be recovered from a month lost to race recovery and various failing body parts, and I'll be able to do a ftp test that should give me some feedback on this scheme. What I can tell you, at this point, is that it takes only a couple minutes to get used to them.


I am running Rotor QXL rings on both a Quarq and a SRM (big only, small is a regular Q-ring and a round ring on the other). Both seem to match up pretty well to each other. I did also compare the SRM to an old wired PT Hub (my trainer wheel) and those are pretty close consistently within few watts for most efforts under 300 watts (a few more difference at sprint speeds....aka 500+).

At first I ran round rings with my Quarq when I first got before I got it then back to QXL ring (waiting for my new ring to get in is why I ran this way). No noticeable increase in power reported on my Quarq on QXL vs round. Perceived effort felt about the same with the power levels pretty much the same. I just like running QXL rings (been doing it for 3 years) and prefer them to try and save my knees more than anything (not for hopes of extra power). They work for me but I can't say it made me faster or slower....just my knees like them a little better.

Also QXL rings (the big chainring at least) comes with the Rotor derialleur spacers. Otherwise SRAM makes one too that is easier to buy than the Rotor ones individually.
Last edited by: loxx0050: Jul 12, 17 6:55
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