Shimano R8000 - Noisy Rear Cassette

[cgates66]

I recently built up a bike with a mechanical Ultegra R8000 disc groupset. Annoyingly, I can’t seem to get rid of some chain / sprocket “grinding” noise in the 11, 12 and 13-tooth sprockets. The other gears seem quiet, and I like a silent bike. The cassette is an 11-25.

Upon inspection, it looks like the derailleur is well-aligned – at the back of the cassette, there is just about 0.5mm of clearance on each side of the chain to the higher and lower cogs. At the front of the cassette, however, where the chain runs up to the front chainring (about 1 o-clock, when viewed from the driveside), the chain appears to be pulled inboard a little bit, causing it to partially hang-up or interfere with the next largest cog in the cassette. As the chainline straightens out, in the 14-tooth and larger cogs, this goes away.
I visually inspected the chainring, and it doesn’t appear to have wobble, however this noise is most pronounced when the crankarm is ~3 o-clock.
Adjusting cable tension, B-tension, and high-limit don’t seem to have a huge impact (curiously, somewhat higher cable tension seems to help, to a point). Shifting is fine – although I am running >10mm of b-limit spacing as running it close is very loud indeed, and shifting performance even at a greater pulley / sprocket clearance is no problem.

Has anyone else experienced this issue? I am pulling my hair out.
One final detail – have not lubed the chain. This is an out-of-the-box HG701 aligned correctly (lettering facing ‘out’), with the Shimano quick-link tight.

[NHAero]

If this is the 11-34 cassette, there is a known issue in the 27T cog. I have this cassette on two bikes and it takes careful set-up to have a quiet drivetrain. I haven't experienced what you are experiencing in the small cogs. That said, I found the whole drivetrain noisy on my Firefly, with the 11-34 cassette and the same KMC 11s chain as on my Anderson. The difference was the crankset - TA 10s chainrings on the Anderson (44-33), SRAM Red 11s chainrings on the Firefly (46-34). It took a couple hundred miles for the noise to subside, but it did.

[Hilltopperny]

When mine was doing that I went through a similar situation. I noticed while swapping the wheels to 650b that my cassette lock ring was not tight enough and there was just enough play that when I put power down it was causing a creak at around 3 O’clock. I would remove the wheel and make sure it is definitely on there tight enough.


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[cgates66]

That's a good thought - I actually performed that operation (also to check that the sprockets were on right, spacers etc. all in the right places) - it is tight. I wonder if it's not something solved by some wet lube and just miles to get everyone kind of meshed together - but it is weird.

[Hilltopperny]

That's a good thought - I actually performed that operation (also to check that the sprockets were on right, spacers etc. all in the right places) - it is tight. I wonder if it's not something solved by some wet lube and just miles to get everyone kind of meshed together - but it is weird.



Yeah, it’s weird if all the spacers and rings are all in the correct position. Maybe some lube and a little more use and it will go away?


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[oldpotatoe]

I recently built up a bike with a mechanical Ultegra R8000 disc groupset. Annoyingly, I can’t seem to get rid of some chain / sprocket “grinding” noise in the 11, 12 and 13-tooth sprockets. The other gears seem quiet, and I like a silent bike. The cassette is an 11-25.

On the big ring, I assume? Short-ish chainstays, small bike?..If on the small ring, not uncommon and the chain 'might' be tickling the big ring when on the small ring....

[BigLips]

I recently built up a bike with a mechanical Ultegra R8000 disc groupset. Annoyingly, I can’t seem to get rid of some chain / sprocket “grinding” noise in the 11, 12 and 13-tooth sprockets. The other gears seem quiet, and I like a silent bike. The cassette is an 11-25.

Upon inspection, it looks like the derailleur is well-aligned – at the back of the cassette, there is just about 0.5mm of clearance on each side of the chain to the higher and lower cogs. At the front of the cassette, however, where the chain runs up to the front chainring (about 1 o-clock, when viewed from the driveside), the chain appears to be pulled inboard a little bit, causing it to partially hang-up or interfere with the next largest cog in the cassette. As the chainline straightens out, in the 14-tooth and larger cogs, this goes away.
I visually inspected the chainring, and it doesn’t appear to have wobble, however this noise is most pronounced when the crankarm is ~3 o-clock.
Adjusting cable tension, B-tension, and high-limit don’t seem to have a huge impact (curiously, somewhat higher cable tension seems to help, to a point). Shifting is fine – although I am running >10mm of b-limit spacing as running it close is very loud indeed, and shifting performance even at a greater pulley / sprocket clearance is no problem.

Has anyone else experienced this issue? I am pulling my hair out.
One final detail – have not lubed the chain. This is an out-of-the-box HG701 aligned correctly (lettering facing ‘out’), with the Shimano quick-link tight.


Are the chainrings, cassette, and chain all brand new? That almost sounds like chainsuck from a new chain on a worn cassette. Out of the box Shimano chains have quality lubricant on them, so adding more wouldn't make a huge difference. I'd recommend setting up your B tension properly with the 6-8mm gap. Does this happen in just one chainring, or both?

[zap]

I had this issue with my Trek when it was new. I fiddled with it and took it to the shop 3 times. The third time the mechanic called Trek and they told him to install a new ultegra rear derailleur. That fixed it.

Apparently there are/were some faulty 8000 rear derailleurs. Too me it looked like there was too much slop in the first derailleur.

A year later (last spring) I installed a new Ultegra 8000 rear derailleur with a longer cage on my wife's bike and that one was thankfully silent.