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.

Tawraste666

Any chance you can do a video of this?
If you can't post links, you can alter the link by popping a space in it.

Being allergic to spending money, my first step would be to take things apart so I know it's all put back correctly.

JoeTBM 

You said the hanger appears straight but has it been checked (and adjusted) with an derailleur alignment tool? This would be my first step in this case, I find you cannot depend on a visual of the alignment alone.

dsaul

Is the chain routed correctly between the two pulleys on the rear derailleur? It sounds like you have the chain routed in front of (and rubbing on) the little tab on the derailleur cage.

tajimirich

A couple of dilettente ideas:
- Is a cable-end on either derallieur touching the chain?
- could you have a loose reflective light or valve screw on a wheel?
- could your bracket be worn out/second hand?
- is it possible that your front derallieur chain ring thingo might be a bit high or low, causing the chain to drag on the top or bottom of it? that you've only been checking for a lateral touch?

considering that it's such a consistent thing, it seems obvious enough that the chain must be causing it. 'dsaul' seems like he's onto something...

cxwrench

How could it be this if, as the OP posted and I bolded below, it happens in every other cog, not all cogs?

I think it's cassette wear. Sounds like it's in the cogs you use most often, right? And again, it can't be the hanger alignment if it's indeed happening as you describe.

bboy314

Sounds like a worn cassette to me too, I’d install a new one (and maybe chain too) and see what happens.

jccaclimber

This is my first guess. Worn rear cassette is on the list as well.
A picture and video would help.

Does it do it shifting high to low as well as low to high, or in just one direction?

dsaul

It shouldn't have much effect on the actual shifting. It will make noise and create drag on the chain

The chain shouldn't touch anything between the two derailleur pulleys. Turn the pedals and watch the chain go through the derailleur. If it touches anything other than the pulleys, it is routed incorrectly.

This is a pic of my older XT derailleur chain routing.

Iride01 

Is the loud noise you are complaining about when the bike is in the maintenance stand in the quiet of your home, or when out on the road with background noise and the wind in your ears.

IMO, people want bikes to be stealthy quiet, but they aren't going to be perfectly quiet.

Dreww10

Here’s the cassette. Forgive the quick cleaning job for a photo.

Dreww10

While riding. It’s so loud others on a group ride would wonder why I haven’t been to an LBS.

Iride01 

Have you checked the chain ring bolts to make certain they are tight? I had several loose bolts on mine that made creaking noises in random gear selections at seemingly certain power outputs. Also check your cassette lock ring.

Most recently I found a lock ring on my rear center lock rotor loose. But that was a different issue and symptoms altogether from what you are describing.

Dreww10

i have not, but the sound is 100% certain at the cassette/derailleur.

jccaclimber

Can we get a picture of the rear drivetrain with everything installed? A video would be better, but a picture or two might clear things up.

cxwrench

Did you read the first post? OP says it happens every other cog. Can't be the chain routed incorrectly if he is indeed telling the truth about when it happens.

jccaclimber

I did, thank you for asking. I also don’t see any great harm in verifying what I asked. All sorts of strange things happen when you route things wrong. People sometimes provide an imperfect description as well. Frankly, anything bad enough that other people around you are asking why it hasn’t been addressed is IME diagnosable in under 30 seconds by a reasonably experienced individual, so we may need to read between the lines a bit and accept the OP as a human rather than perfect narrator.
The OP was pretty thorough in their list of already searched places, but is clearly missing something because they haven’t found the issue.
For some additional background, I’ve had someone ride into the local co-op with the description “loud in the upper gears, but not as bad in the lower ones”. The problem did turn out to be improper chain routing through the derailer. I figured it was equally loud everywhere, but the rider clearly did not.

BTinNYC 

A blindfolded dart in the air;
Could a spacer mistakenly still be in the hub? (I've had a spacer that was not cut for the cassette rivets causing a barely noticeable wobble and similar badness).

I hate noise from the bike. Today my front hub started rattling on a downhill. I braked to a stop and the rattling was there when I bounced the front tire and it took a long 30 seconds to find the bottle cage was loose.

P.S. I'd try a different chain.

Dreww10

No spacer.

Dreww10

Yes, the chain is in the cage correctly. I’m by no means new to bike maintenance, but this one has me stumped.

3alarmer 

...it would be great if you could eyeball these for wear, but you can't.
I would buy one and change it out as an experiment. I don't know what they cost now, but they were pretty cheap not too long ago.

3alarmer 

...that's actually pretty good life for one of these. I would change it out as my next step at a remedy.

jccaclimber

Do minor derailer trim adjustments let you change which sprockets make the most noise?
Any unusual noises when pedaling backwards?
You mentioned more vibration in the stand than normal, does this also go every other gear?
Independent of front ring position (assuming not 1x)?
You torqued the lockring, did you verify he sprockets are tight as well, IE don't move by hand?
Condition of the freebody? IE, not all grooved up like the cheap early aluminum ones.
Does the noise occur in the stand when turning by hand? What if you drag the brake to induce a load? I assume it's gone when coasting, but does it happen under medium load, light load? Does it change?

Dreww10

No.
Doesn't appear to be.
It's not every other gear exactly, but just some random gears mostly toward the middle.
It is louder in the big front ring.
Yes, lock ring is torqued, no play in cassette.
Freehub body is in great shape.
Happens under all load. Obviously far more noticeable while pedaling, but if I run through the gears by hand, I can tell which ones get louder. This was what confirmed for me it's unlikely to be movement in the cassette, because my hand turning the crank might be 1 watt, which wouldn't be enough to twist the cassette unless it was very loose.

jccaclimber

I forgot that this was a di2 part, so my usual cable assumptions are out. What are the odds that something's not right with the derailer?
Stupid question, but you can access all 11 gears and it doesn't skip one? I wouldn't expect that, but I'm starting to fish/cover all bases here.
Is the sound the "I want to shift but can't quite" sound, or something else?
A video with sound would really help (host on YouTube or similar).
Since it sounds like you have some riding buddies, can you swap wheels with one of them and see if it still does it on their wheel (ie gets you a cassette swap, and a few other variables removed as well? You might need to re-adjust the derailer when you do this, but that's a 5 minute activity. You don't actually need to adjust the limits as long as you don't shift into the end sprockets, just the trim.