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Shimano 12 speed - issues upshifting with clutch ON

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12 speed clutch drive train rear derailleur shimano slx/deore
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Mann

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Discussion starter · #1 ·
I ride an SLX 12 spd groupset. I've noticed that when upshifting from the biggest cog, it will take several clicks to actually shift (sometimes 3-4). If I give the rear end of the bike some bounce, it will also respond and shift. This is most often on the first climb of the ride, which is a smooth, 1 mile climb.

The bike has a new chain, new shifter cable, and indexes perfectly in the stand.

I tried riding today with clutch off, and the problems went away.

Is this a clutch service issue or something else that I am missing? Has anyone else had this happen before and how did it get fixed?
 
#5 ·
Mann said:
Length is perfect; Need to check B tension. Would that explain why it shifted perfectly with clutch off?
Click to expand...
Could be. I’ve found my 11 & 12 speed drivetrains are far more sensitive to b-tension adjustment than drivetrains of old.
=sParty
 
#6 ·
I can't speak to 12 speed but on my 11s shimano I had a very similar issue. This was after going from an 11-46 to 11-42. A small adjustment of the b screw to bring the derailleur closer to the cassette made the shifting work flawlessly with the clutch on. As a bonus it also quieted down the chain slap a bit. Definitely worth tinkering around with if you haven't yet.
 
Discussion starter · #7 ·
Slowanimalswin said:
I can't speak to 12 speed but on my 11s shimano I had a very similar issue. This was after going from an 11-46 to 11-42. A small adjustment of the b screw to bring the derailleur closer to the cassette made the shifting work flawlessly with the clutch on. As a bonus it also quieted down the chain slap a bit. Definitely worth tinkering around with if you haven't yet.
Click to expand...
Thank you both, will mess with that tonight
 
#9 ·
I too had sluggish shifting from the biggest cogs to smaller cogs with my 1x12 drivetrain (SLX shifter and rear derailleur, deore 10-51 cassette. Like other have mentioned, b-tension is critical with this setup. I found that adjusting the b-tension per Shimano's guidelines (longest tooth on the biggest cog even with the line etched on the derailleur) left the upper jockey wheel much too far away from the cassette for crisp shifting.

I now adjust the b-tension using Kyle Warner's setup guide (see link). In a nutshell, I first remove the droop from the chain when it is in the biggest gear (smallest cog) by tightening the b-tension bolt progressively. I then give it just a little more tightness to make sure the chain doesn't bounce excessively in the smallest cogs. Lastly, I check to make sure there is adequate clearance between the chain/upper jockey wheel and largest cassette cog teeth. This results in the cassette teeth a fair bit lower than the line etched on the derailleur...and much better shifting.

 
#10 ·
Sounds like you need to service the clutch. How is the movement of the cage when you press it with your hand? It should be smooth and not jerky with the clutch on. There are a lot of videos how to do it, just make sure that you don't lubricate the roller bearings inside the clutch, they should be dry. Take a picture and be careful to assemble it correctly.
 
Discussion starter · #11 ·
hkmeup said:
I too had sluggish shifting from the biggest cogs to smaller cogs with my 1x12 drivetrain (SLX shifter and rear derailleur, deore 10-51 cassette. Like other have mentioned, b-tension is critical with this setup. I found that adjusting the b-tension per Shimano's guidelines (longest tooth on the biggest cog even with the line etched on the derailleur) left the upper jockey wheel much too far away from the cassette for crisp shifting.

I now adjust the b-tension using Kyle Warner's setup guide (see link). In a nutshell, I first remove the droop from the chain when it is in the biggest gear (smallest cog) by tightening the b-tension bolt progressively. I then give it just a little more tightness to make sure the chain doesn't bounce excessively in the smallest cogs. Lastly, I check to make sure there is adequate clearance between the chain/upper jockey wheel and largest cassette cog teeth. This results in the cassette teeth a fair bit lower than the line etched on the derailleur...and much better shifting.

Click to expand...
I’ll check this out, thanks

EJ_92606 said:
Sounds like you need to service the clutch. How is the movement of the cage when you press it with your hand? It should be smooth and not jerky with the clutch on. There are a lot of videos how to do it, just make sure that you don't lubricate the roller bearings inside the clutch, they should be dry. Take a picture and be careful to assemble it correctly.
Click to expand...
If/when the b tension doesn't fix this will be next!
 
#12 ·
I had this happen with my bike, also with an SLX transmission.

It was a misaligned derailleur hanger. Bent it the correct way, and the issue went away.

The problem had nothing to do with the clutch. If the hanger is only slightly out of alignment, the clutch just makes it a bit harder to shift because of the added tension, and that is enough to cause the issue.
 
#17 ·
Check if you derailleur moves at all when you downshift from the biggest cog.

If it jams in one position, when there are several possibilities:

1. Old and rusty cable and housing. The derailleur spring is too soft to overcome high friction and pull the cable back from the shifter. Replace the cable and the housing.

2. Dry parallelogram pivots (my case was that). If you ride in very wet conditions or spray your bike with soap or degreaser, the grease from the pivots washes away and the derailleur becomes sticky. The upshifting is ok, because you pull it by the shifter, but downshifting suffers from the friction. Drop some chain lube in the pivots and move the derailleur by hand to distribute it. Strangely, but somehow the clutch affects it. My derailleur was more eager to jam with the clutch on. If it is the case, also clean and regrease the cage axle.

3. Rusty or worn out clutch. Normally, it should not affect downshifting, but in the worst case it can. Try cleaning and greasing it. If it does not help, replace it. Shimano part no. is Y3GF98040.

Here is a good disassembly guide: NSMB.com - Shimano Derailleur Clutch Service
 
#18 ·
Mann said:
I ride an SLX 12 spd groupset. I've noticed that when upshifting from the biggest cog, it will take several clicks to actually shift (sometimes 3-4). If I give the rear end of the bike some bounce, it will also respond and shift. This is most often on the first climb of the ride, which is a smooth, 1 mile climb.

The bike has a new chain, new shifter cable, and indexes perfectly in the stand.

I tried riding today with clutch off, and the problems went away.

Is this a clutch service issue or something else that I am missing? Has anyone else had this happen before and how did it get fixed?
Click to expand...

Last bike I had , had the same problem. I even replaced the shifter cable and housing too. I spray lube the linkage. Gone
 
#19 ·
Mann said:
Thank you both, will mess with that tonight
Click to expand...
I have to point out that as others have mentioned, 12spd drivetrains, especially, are sensitive enough to b-screw adjustment that you don't just "mess with it" and hope to get it right. You have to know what the recommendations are and put it there. Both SRAM and Shimano have guides/measurements for this, and they're a little different from each other.
 
#20 ·
I had the same issue with a deore 12s. I re lubed clutch and played with b screw which didnt help. What ended up being the fix for me was making the L screw a little tighter - even though it had seemed perfect already. Hope this helps
 
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