Long story short...I've just swapped out my worn 12 speed SLX cassette and SLX chain with like-for-like new.
It was shifting ok but as I have some big trips coming up thought it was time to refresh it.
The chain is now jumping around on the sprockets where the spacers are.
They spacers are different thicknesses - there's even a YouTube vid highlighting the issues caused by having the spacers in the wrong positions, causing jumping chains and people pulling their hair out (not literally!). Mine are correct as I've triple-checked. The mech or hanger haven't been damaged since the last ride. Someone has suggested jockey wheels or chainring, but wouldn't they cause issues in the other gears too? Not sure what to do...I have another unused hanger (Privateer 141), new XT chainset and new Deore mech, but hope there's something dumb I've overlooked before replacing that lot...
Is the chain the right length / same number of links?
Cassette same size / same number of teeth?
Is the cassette or chain linkglide or hyperglide (think they are different / incompatible?)
hope there's something dumb I've overlooked before replacing that lot...
Cable routed the correct way around the nub and into the retaining bolt? I've done this before (it's not always intuitive) and it caused what you describe.Â
My recent Slx shifting issues were a sticky clutch. If it works with the clutch off, have a look at the videos for how to service the clutch
^^ Sticky clutch? as in letting the chain stay loose? (ive dropped a chain of my front ring a couple of times recently)
Mistake i usual make when reinstalling a microspline cassette is to not notice the smaller sprockets aren't aligned correctly as per the pattern with the slightly wider gap; they'll still go back on but will cause the issue you describe and, when looking closely you see a slight gap on one side on one of sprockets.
Rode the whole of the Royal Chilterns Way with that issue...extra careful now 🤦
Cable wrong side of the pinch bolt or a stiff link as the smaller sprockets require more articulation.
I still make the mistake (with 10/11 speed) of threading the chain through the derailleur wrong, and not noticing 'till I'm half way through a ride. All these years... and still an idiot. With the 12 speed mechs it's much harder to make that mistake though.
Not touched the cable routing, hanger, clutch...chain is the right length and connected properly with the same 10-51 cassette.Â
Cassette mounted properly? I know the microspline freehub can be a bit tricky to make sure the cassette isn't fitted wonky. Took me a couple of goes to get mine right the first time I fitted it
Chain on the right way round - writing facing outwards?
Sticky clutch is definitely worth checking. I intend to wean myself off shimano 12s mechanical derailleurs as they need lubricating so often.
But have you checked the B-gap is correct? You should have the 51t line on the back of the derailleur. If it was correct with a stretched chain then it most likely won't be with a new chain so will need adjusting.
I still make the mistake (with 10/11 speed) of threading the chain through the derailleur wrong, and not noticing 'till I'm half way through a ride. All these years... and still an idiot. With the 12 speed mechs it's much harder to make that mistake though.
I'm bad for that, but once I had to break a chain on a trail after it got stuck behind the cassette and managed worse - I routed it the wrong way around the seat stay!Â
No experience with 12 speed but I once swapped an XT 10 speed 10 like for like & ended up having to completely re-index everything (including tweaking the limit screws). I've no idea why, but once done it worked perfectly.
Mistake i usual make when reinstalling a microspline cassette is to not notice the smaller sprockets aren't aligned correctly as per the pattern with the slightly wider gap; they'll still go back on but will cause the issue you describe and, when looking closely you see a slight gap on one side on one of sprockets.
It's very easily done. Even when I know to pay extra attention to sprocket seating and alignment I've still ended up getting it wrong. Well and truly bolloxsed up the shifting. It'd be the first thing I'd check in the OP's situation.
I've just had SLX shifting issues that turned out to be due to the cage pivot being super stiff. I stripped the mech down (turorials on YouTube) and spent a few minutes spraying in GT85 then isopropyl alcohol (brake cleaner) and exercising the pivot until it was free again. There was a lot of muck in the cage return spring 'pocket' that probably wasn't helping. The mech is coming up to two years old and working like new again, pretty fair I think. Might even treat it to some new jockey wheels soon.Â
The spacers were in the right places so gaps even. Nothing else had been adjusted. As I had a new mech, hanger and chainset to try, I swapped out the jockey wheels as the first port of call and that seems to have sorted in...in the close up and down a few kerbs anyway!
Is the chain definitely 12 speed? The chain, not the packaging.
@Burger something similar came up on a recent thread: How to prevent a rusty spring?
I swapped out the jockey wheels as the first port of call and that seems to have sorted in.
Good result. Having experienced the common issue (well, more that I've seen it discussed before online) of chain jamming between the top jockey wheel and mech plate with both SLX and Deore 12s mechs, I feel swapping out jockey wheels for better quality ones is a good move anyway
What lubricant do you use? Sticky clutch seems to affect all my Shimano derailleurs after a while and the Shimano recommended grease is hard to find.
