12-Speed SLX derailleur/chain noise in smaller cogs...

DoctorJD · Sep 21, 2023

I recently bought a new Stumpy that has SLX 12-speed on it. When the chain is in the three smallest cogs on the cassette, it rattles like crazy. The noise is not pedal-induced, it occurs when I'm at speed when vibration from the trail comes into play. As soon as I shift up to the fourth cog, it disappears altogether.

I bought this direct from Spesh since I don't live close to a dealer, and I realized from the outset that they shipped it with the chain long.

My method of measuring chain length was to go large cog-to chainring (bypassing the derailleur) with the suspension collapsed, then adding 4 links. After cutting the chain to size, it the noise cleaned up a bit, but it's still really noticeable.

Also, as part of my troubleshooting efforts:
B-screw is adjusted to spec.
Cassette is fully seated on the freehub body, and tight.
All derailleur bolts are tight, nothing loose there.
Clutch is engaged.

I can't figure it out. Operationally, shifts like a dream, but it's just noisy. I'm still not convinced that the chain isn't still too long. It's like there's not enough tension on the derailleur cage when it's in those smaller cogs. I'm attaching pictures of the chain both in the large cog and the small cog to show the relative derailleur angle.

I've been running Sram for the past 15 years and I've never encountered this. Is this just a noisy drive chain, or is my chain still too long? Thanks!

Phanis13 · Sep 21, 2023

Probably you need to loose another link or two. But I would be very careful as this is a full suspension bike. Remove one at the time
Also, maybe the clutch of the rd is weak. You can check that as well

jimPacNW · Sep 21, 2023

Have you checked to make sure that the rivets holding the center cogs are tight? If cog #4 is rattling, shifting onto that cog would stop the rattle. Here's mine, 2020 I think, on a Giant Trance 2 (110 rear travel iirc). Not noisy, 30t front gear

.

Amt0571 · Sep 22, 2023

Misaligned derailleur hanger? if it's slightly misaligned it could cause your derailleur to be slightly out of alignment on the lower cogs. If this happens, the chain may rub on the adjacent sprocket making noise.

NC_Foothills_Rider · Sep 22, 2023

My friend just bought a Ripmo AF this spring, equipped with a Shimano drivetrain.

After putting about 100 miles on it, he started noticing the same issue.

We solved that by turning the adjuster knob on the shifter counter-clockwise 1/4 of a turn. The adjuster is notched so you can do it precisely.

In the case of this Ibis, the new cable had stretched a couple of millimeters. His worked fine in the lowest gears 1-7, but like yours, would get noisy in 9,10, and 11.

Anyway that simple adjustment fixed it immediately. Now this bike shifted perfectly when he got it.

If your derailleur hanger isn't bent and the derailleur is't loose or damaged, then it may just be cable stretch as it was on my friend's Ripmo.

Desertride · Sep 27, 2023

If I'm understanding correctly, this only happens on the trail and no on the stand? If so, it seems like it must be the cassette. Those smallest cogs on the Shimano 12sp cassettes are notoriously a real bear to seat correctly.
Remove the wheel, remove the cassette lockring, very very carefully reseat the smallest cogs and tighten the lockring to torque. If anything seems off kilter or a little bit off, back off, triple check that the cogs are properly seated (look up some videos on how to do this by checking the alignment of the small dots on the teeth) and retighten.

DoctorJD · Sep 27, 2023

Desertride said:
If I'm understanding correctly, this only happens on the trail and no on the stand? If so, it seems like it must be the cassette. Those smallest cogs on the Shimano 12sp cassettes are notoriously a real bear to seat correctly.
Remove the wheel, remove the cassette lockring, very very carefully reseat the smallest cogs and tighten the lockring to torque. If anything seems off kilter or a little bit off, back off, triple check that the cogs are properly seated (look up some videos on how to do this by checking the alignment of the small dots on the teeth) and retighten.

Yeah, it's the next thing on my trouble-shooting list. I feel good about the cassette install only because I had so much trouble putting it all back together when I disassembled it to get the dork ring off. Those spacers with the variable thicknesses messed me up, so I already did a YouTube tutorial on how to properly reassemble them. It feels solid and none of the cogs feel remotely loose, but just for the sake of checking it off the list, I'm going to do it anyway.

DoctorJD · Oct 1, 2023

Thanks to all who replied. I figured it out. After I put the bike on the stand and cycled the gears through those first four cogs, I came to the realization that it had nothing to do with derailleur tension or chain length. The derailleur (in the 3rd cog) had the chain taut and the cage had plenty of resistance. But I could still get it to rattle in that 3rd cog. It could only be one thing.

Desertride got me thinking that maybe...juuuuust maybe...I missed something on that cassette. The fact that it was the four cogs on the cassette that were independent of the rest of the cassette body should have thrown up red flags. To the touch, the cassette was tight with no looseness at all. That being said, I put my locknut tool on the cassette and gave it a 1/4 turn.

I put the thing back on the bike, bounced it up and down, and...silence. Took it out yesterday and rode some really janky singletrack and it was quiet as a mouse. You'd think after wrenching all these years, I'd know to check the most obvious things first (it ain't got no gas in it, mmmhmm) but no, I have to overthing it 😂 Live and learn.

12-Speed SLX derailleur/chain noise in smaller cogs...

DoctorJD

Phanis13

jimPacNW

Amt0571

NC_Foothills_Rider

Desertride

DoctorJD

DoctorJD

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