Bike Forums - View Single Post - Does anyone have experience with Stone oval 1x chainrings?
Old 03-08-18, 09:53 AM
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RoadLight
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Greetings again,

I received the following answer from the "China Cycling" channel on YouTube about the Stone oval 1x chainrings:

I think It's slightly thicker than a standard 2x chainring. I was able to mount it on a 2x crank spider with the original bolts, as well as the slightly shorter ones STONE provided. However, I also have an old-style SRAM Red 22 crank, and can't mount the stone chainring on it, but not because of thickness, but because the innermost circle of chainring fouls on the crank arm (really hard to explain), You can dremel away the two holes next to the hole that you use... but of course, this means you'll no longer be able to adjust the angle of your oval ring. If you look for the Rotor QRings and then compare to the rotor qrings OCP3 - you'll see the difference and why strange cranks sometimes require strange rings.

There's no offset on the chainring I got, but their latest chainrings have an optional offset for maintaining chainlines in various setups.
From the author's description, it sounds like the Stone oval 1x chainrings will not fit a SRAM Red 22 crank without modification and that modification may prevent you from being able to adjust the orientation of the oval. However, the author has trouble describing why this is so.

The last paragraph was also interesting. Evidently the original Stone oval 1x chainrings had teeth that were centered to the disc of the chainring. This means there were not optimized for a 1x chainline (and may not be optimized for 2x, either). In my experience with SRAM cranks, the teeth of an outer 2x chainring are biased toward the outside and the teeth of a 1x chainring are biased toward the inside. I don't know if this is true for all other manufacturers but the 1x situation should be fairly universal---a 1x chainring mounted to a standard crank will need to have teeth that are off-center toward the frame in order to properly center the teeth to the chainline of the center of the cassette. However, it doesn't need to be the exact center because some manufacturers (like SRAM) will locate the 1x chainring teeth 1-2 mm to the outside of the cassette center. This favors the smaller cogs a little. (Perhaps cross-chaining a small cog is more problematic than cross-chaining a large cog because the smaller cog has fewer teeth to hold the chain.)

While the last part stating "...their latest chainrings have an optimal offset..." sounds promising, none of the Stone's distributors that I could find discussed this issue. If you purchase one of these chainrings, you'll have not idea which version you'll receive.

I've contacted one of Rotor's distributors to obtain more information about Rotor's Aero QX1 chainring for 1x systems to see if it will fit a Red 22 crank. As I get more information I'll update this thread for the benefit of others who may follow a similar path.

Incidentally, the first professional use (that I'm aware of) of a 1x drivetrain with a large chainring for road use was Tony Martin's TT bike for the 2017 Tour de France (with a SRAM Red eTap system minus the front derailleur). But the sport that seems to be embracing this setup the most is Triathlon where a 1x is becoming more and more common for routes that are not mountainous.

Kind regards, RoadLight
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