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10 speed rings on 11 speed drivetrain (Ultegra R8000)
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I've been using a GXP Quarq Dzero with 10 speed SRAM rings with my CAAD10 which is 10 speed and had swapped it back and forth to my CAADX 11 speed 5800 no problem. I had probably done at least 2-3k miles with the 10 speed rings on the 11 speed drivetrain and didn't notice anything different.

Then I got a new road bike with Ultegra R8000 mechanical. So I just pulled the Ultegra crank, swapped the BB, then popped in my Quarq with 10 speed rings. I had just replaced the rings in February, so they only had a couple thousand miles on them...and I typically swap them after around 15-20k miles. At first, shifting was perfect and the drivetrain was ultra smooth and quiet. Other than tightening the barrel adjusters once the cables set in, no adjustments were needed after the first week.

Then slowly the drivetrain started to make noise. The shifting of both the FD and RD were still crisp. No skipping gears or dropped chains. No unusual chain rub on the FD. It just seemed like the chain wasn't moving smoothly through the rings, cogs and pulley. I cleaned everything up and added chain lube like I normally would but it made little to no difference. At first the noise was just in the big ring and maybe the 13-15t cogs...then it slowly started to be noticeable across all the usable gear combinations including the small ring. Didn't matter if I was spinning at 150 watts, or putting more power down at 300 watts.

Because the shifting was still crisp, I figured it wasn't anything with limit screws or cable tension and swapped the factory Ultegra chain for an 11 speed KMC chain. The mechanic at my shop concurred that the cable tension and limit screws were fine. The existing chain was checked with a chain checker and was not near the 0.75 replace indicator, but was above the 0.50. About what I expect for 800 or so miles of use over 4 weeks based on how long my 10 speed chains would last me. I usually swap chains after 2000-2500 miles which I know is quite frequent, but even with constant cleaning, that's how long they last me before the chain checker says it's time to replace. So I decided to swap the chain to a KMC 11 speed and once replaced, instantly the sound went away and everything was great with no further adjustments. Until about 5 days later when slowly the process of noise started creeping up again. Not in all gears yet, but slowly its starting to get worse again now 10 days later.

So my next thought is that it's my chain rings that might be causing some type of abnormal wear on the chain. It's also possible that the 11 speed chain is just not running through the 10 speed rings smoothly, but since the sound doesn't occur with a brand new chain, I'm doubting that. Also, just by listening when the bike is on the stand, it sounds like the noise is coming more from when the chain runs through the RD.

I always thought, and in my past experience, that 10 speed rings were okay with 11 speed chains. Many aftermarket chainrings are advertised to work with 10 and 11 speed, and sometimes even 9 speed. I know that the new Ultegra R8000 crank did make some changes where the small ring was 0.4 mm farther inboard, but the large ring was kept in the same place. So since the noise happens while I'm also in the large ring, and it's not a chain rub issue (verified while the pedaling the bike in the work stand in the 50/15 gear), I don't see how the spacing difference would solve the issue.

Any advice? Really hoping not to drop $120+ on new rings if it's not going to solve the problem. Especially since the current rings are only about 4 months old and the options like Praxis rings say they work with 10 and 11 speed.
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