Dreww10

Been racking my brain trying to figure out a constant and very annoying drivetrain noise on a bike with a brand new Ultegra R8050 RD. 52/36 crankset, 11-30 cassette, HG701 chain with quick link.


The noise occurs in about half of the cogs, but for the most part, not in any two consecutive cogs (meaning it's loud in one, shift over one it gets quieter, then the next over from that gets loud again, and so on).


It has changed a little over a few weeks of tweaking, but is mostly the loudest in the center 4-5 cogs, where there is the least cross-chaining and it should be quietest. It is much louder in the big front chainring. It's a constant grind/rattle, and doesn't sound like a misadjusted RD where the chain plates are clicking and catching the next cog, but rather, sounds like a chain going though the cage and/or cassette at an unhappy angle, the chain slipping on the cassette, or bent cassette teeth. There is also noticeable drag on the drivetrain in almost all gears, but for sure moreso in those that are loud. For some context, it's 2-3x louder in the 14T-21T range in the center than it is in the usually very loud 52/30 cross-chain position. It's also not super happy noise-wise at 52/11.


Few points:

- The cassette is properly torqued

- The hanger and the RD are both tightened; jockey wheels are also tight (have not touched from Shimano)

- Chain is installed in the correct orientation, and is correct length

- The hanger, from all appearances, is straight - plus it's not loud in every gear like a bent hanger ought to cause (hanger is low mile, has never been bumped, crashed, anything)

- Cassette has maybe 7-8k miles, and shows no signs of sharp teeth, shark teeth, or unusual wear

- No obvious signs of any bent teeth on cassette

- Chain does not yet have 0.5 on wear (I also tried a brand new HG701 chain on it and it got somewhat louder)

- I have done micro adjustments across the entire range in the loudest gears, while pedaling, and it never gets any quieter

- I have played with the H/L limit screws to dial them in just right, but that has made no difference

- B limit is at recommended position in relation to the big cog...not sure if B limit can have any effect on potential noise

- The rear shifting is not buttery smooth in any gear, especially going from up from small to bigger, but the noise is my priority in resolving

- Turning the cranks by hand in the workstand, there appears to be a little more visual "vibration" in the chain as it goes around than normal


Any ideas? If I can't sort it out, my first step would be a new hanger and then a cassette.