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I got an Shimano R7000 groupset and have the following problem:

After degreasing my chainrings (54 – 36) and the cassette (28 – 11), the drivetrain makes normal noise. However after around 30km, the rear cassette (or chain?) begins to make noise in the lower gears. It is very noticable in the 36 - 28 (the smallest gear), 36 - 25 (2nd smallest gear), and 36 - 23 (3rd smallest gear) combination. Interestingly, the 36 - 21 or any higher combination does not produce the crackling sound.

I made a video which illustrates the behavior. I‘m starting in the 36 – 21 combination which makes normal noise. When shifting in a lower combination, you can hear the crackling sound. At the end, I shift back in the 36 – 21 combination which is totally fine.

Questions:

  1. Does anybody experience a similar behavior when the drivetrain is dirty?
  2. Is there anything to fix this crackling sound?

Additional information 2019-07-09:

  • Indexing: I don‘t think the indexing causes the crackling sounds, because i experimented with the barrel adjuster and it had no effect on the crackling sounds - it only effected my shifting
  • L-limit screw: Is set correctly (see photo below)
  • Derailleur cage: In my eyes, it seems a little bit bent. It is the normal position of a Shimano cage? (See photo below)

my derailleur position


Additional information 2019-07-30:

  • I changed the chain, no effect. Can the spokes produce such a pinging sound? If yes, how can I check spoke tension?
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    Sounds to me like the derailer needs adjusting. (Stupid question: Did you relube everything after cleaning?) – Daniel R Hicks Jul 8 at 17:11
  • Yes, i did relube the chain and the jockey wheels. When the drivetrain is fresh (degreased and lubricated), no crackling sounds exists. It only makes noise when the drivetrain is dirty. – piptoma Jul 8 at 18:50
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    Did you remove the chain during the cleaning/re-lubrication? If so, check it very carefully for a loose quick link if you used that, or if you used a pin check that the pin used to rejoin the chain is still properly in place. If either the quick link is not fully closed or a pin is protruding a bit, eventually instead of making noise as it whacks something as it goes past, it might actually catch something solidly and wreak havoc on your drive train - or worse. It's not a likely cause, but the consequences can be catastrophic. – Andrew Henle Jul 8 at 20:46
  • @AndrewHenle No, I‘ve never removed the chain when cleaning it – piptoma Jul 9 at 5:14
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    It does kinds look like the cage is not aligned properly, although I'm not sure if it's a little bit of wide-angle lens effect making it seem that way, – Argenti Apparatus Jul 9 at 19:24
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It sounds like your derailleur indexing is bad. The 'crackle' is the chain trying to climb the shift ramps on the next largest sprocket then falling off.

It may be that your derailleur indexing is badly adjusted. You can run through a rear derailleur adjustment process and see if this fixes the problem.

You should also check that your derailleur is aligned properly. The derailleur hanger can get bent so that the derailleur cage is not longer parallel to the rear wheel. If you pick rear wheel of the bike up and look down the line of the chain you can see if the cage is grossly out of alignment if it is not parallel to the chainrings. A bike repair shop can check and re-align the hanger.

Another possibility is that the chain is catching in one of the jockey wheels in the cage. If you hold the rear wheel off the ground and pedal manually you should be able to see this easily.

  • 1
    If the indexing was bad and the chain was trying go climb the shift ramps, would you not expect the ‚crackle‘ to be absent in the 28 (the lowest) cog? And would this hypothesis be consistent with the observation of the drivetrain is perfectly normal/silent when the chain and cogs are freshly degreased and relubed? – piptoma Jul 9 at 18:40
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    @piptoma Can you make the problem go away on the 28 or two next smallest sprockets by adjusting indexing? If not, indexing is not the problem. – Argenti Apparatus Jul 9 at 19:18
  • No, the indexing is independent of the crackling. – piptoma Jul 10 at 14:34
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    @piptoma. I see you have a bike stand. I'd try to replicate the problem on the stand turning the crank manually. You should be able to see what the chain is doing. Is it catching in the cage or is it trying to ghost shift to the next largest sprocket? Can you make the problem go away be manually twisting the derailleur to align it better? – Argenti Apparatus Jul 10 at 15:32
  • I also tried replicating it on the stand, but the crackle only happens under heavy load (i. e. uphill). When inspecting the cage on the bike stand, it seems just fine and shifting performance is very good. Yesterday I noticed something interesting: I reapplied lube on my dirty chain and the crackle disappeared - only to return after around 40km. This got me thinking if my dry lube only lasts about 40km? As a next step I will clean my drivetrain and apply wet lube to test whether it's a "lubing"-issue. – piptoma Jul 11 at 5:57
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I'm going with the suspicion this just some form of front derailleur rub. It's only happening with combinations of the leftmost front ring and leftmost rear sprockets. The temporary relief obtained from lubrication is also consistent with rub. Frame flex is why it doesn't reproduce on the bike stand. Front-side cross-chaining issues are sensitive to frame flex, because the rings basically tilt relative to the plane of the bike's frame when you put your weight into the pedals. The hypothesis is easily confirmed or refuted with a simple front adjustment.

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