Are 12S SLX mechs a bit rubbish or…

have I bent it?

My shifting was getting a dodgy last weekend and last night I thought I’d sort it but couldn’t get it to index properly. Bottom of the cassette was fine but as you went up the cassette it wanted to jump up again into the next cog.

Changed the hanger as I assumed it was bent and changed the jockey wheels as they were flopping all over the place. No real improvement.

I’ve knocked my SRAM GX mech from my other bike and it’s perfect, probably better than ever.

Are they prone to not lasting long or have I just got unlucky? It’s only done about 1200km.

Appreciate what you say about replacing the hanger but if you’re sure the cable is good I’d check the alignment. I was a sceptic but they seem to be really susceptible to misalignment.

I’ve got two on the go and they’ve both been fine. One had enough force through it to significantly bend a hanger but the mech survived unscathed.

I had one that was terrible, but couldn’t see anything at all wrong (usual alignment checks etc all fine). Chucked a Deore on and the problem was instantly fixed. can only guess that it was a tiny bit twisted and it was just enough to completely screw up a handful of gears.

@del yeah the cable is good, I replaced that as well, inner & outer.

 I should probably buy an alignment checker, I have to borrow one at the moment…

Shimano 12 speed mechs are really picky about hanger alignment – but if a GX eagle one works fine then it seems unlikely it’s the hanger. See if you can borrow a hanger tool off someone to check – or a different Shimano mech perhaps? 

Funny you should mention this.

I’ve just set up two Shimano 12sp systems.

Both SLX cassettes (10-51), SLX mech, SLX chain, XT shifter.

First one on the Ragley took a bit of fiddling but then seemed to work flawlessly.

Second one yesterday on the Kenevo – could get it shifting ok at the bottom of the cassette (after a fair bit of swearing), but it wouldn’t index properly at the top. Get it set up at the top, it wouldn’t work at the bottom.

I finally got it to behave after an hour or so of adjusting, but that’s just riding up and down the road. I suspect it on the trail it will start playing up.

I have recently had an exploding GX mech and whilst the hanger looks ok, suspect it may be the issue, so just ordered a new one

@TheArtistFormerlyKnownAsSTR get yourself a park dag 2.2

Yes, they’re utter cack.

Swap for an 11speed and wind in the high limit screw, an option?

Check for damage/kinks/poor cable routing and particularly if on a full susser any worn pivot bearings/rockers etc as this ruins shifting faster than anything else

Hanger alignment check needed – plenty of new bikes arrive ‘bent’ needing a tweak to get them to shift cleanly. 

The joys of 12 speed, when it works, it is bliss. When it starts to play up, you end up replacing everything around the mech to make it stop. 11 speed is so much more dependable, can’t see me moving to 12 speed GRX when my current 11 speed GRX packs it in. 

I had one that kept going wrong. Turns out it was the cable slipping. It’s not that easy getting enough torque onto the bolt to tighten properly, as when you turn the allen key the mech tries to “parallelogram”.

Check the distance between the jockey wheel and cassette, a little bit off and it just doesn’t play ball. 

This is quite a good installation guide IMO.

https://bettershifting.com/installation-guide/12-speed-rear-derailleur-installation-and-adjustment-guide/

Mine got sticky at the pivot, so wouldn’t return well…. I’ve had other 7/10speed DH ones get sticky there too. I’ve never had the same on an SRAM.

Funnilly, all my bikes run SRAM.

Love 12sp when it works, but yeah, it is very picky. Chain length needs to be right, and it’s super, super sensitive to hanger alignment.
Never rely on a new hanger being straight. I’ln my experience they often aren’t!

Pretty good mech IME.

park dag 2.2

On that topic, can ayone comment on the equivalent Lifeline alignment tool that’s approx half the price of the Park Tools one? Reviews are very mixed. https://www.wiggle.com/p/lifeline-pro-gear-hanger-alignment-tool

If you run a 12 speed Shimano – you need a hanger alignment tool.

12 speed Shimano, for some reason, seems to be far, far more picky about this than any other setup, including 12 speed SRAM in my experience.

A Mk1 eyeball ‘looks straight to me’ or just replacing the old hanger is no longer sufficient. Its also quite possible that a brand new unbent hanger will often end up fractionally out of line when bolted up, particularly on frames with thick powder coat paint jobs, alloy Santa Cruz being a perfect example.

Whilst I’ve always owned a hanger alignment tool, the aforementioned mk1 eyeball + years of experience was generally good enough to ensure everything was setup OK – with 12 speed Shimano particularly, I now find the tolerance is so fine between working and not working, you need to stick the tool on.

@a11Y

Reviews are very mixed. https://www.wiggle.com/p/lifeline-pro-gear-hanger-alignment-tool

Lifeline/China special hanger tool from ebay/amazon/CRC etc is perfectly adequate, and should be in all your toolboxes.

Its not for use in a bike shop all day every day, but for hanging up in the garage it works fine, as long as you use it correctly!

On my N of 1 SLX is fine, done 2500km over 2 years on mine. Rarely need to adjust, but if i do then I need to finetune cable tension to get it properly smooth. It can be quite small turns of the barrel adjuster, and needs a bit of trial and error both ends of the cassette

That is the same for 11spd Ultegra on the road bike too.

Thanks @snotrag. Concern about that Lifeline one is the supposed play in it which would surely affect accuracy? I did have a basic mech alignment tool in the past that proved very useful but no idea where it’s gone (don’t think I lent it out but I can’t find it now…). I’ve not been disappointed with anything Lifeline-branded in the past and had that one in my basket until I read the reviews.

My experience is most Shimano 12spd mechs are rubbish.

Incredibly fussy to set up, I’ve actually had better results running a SRAM shifter with them, need a lot more constant maintenance & have a habit of exploding at the lower arm.

Apart from crappy clutches, the SRAM stuff seems far less faff.

I had an SLX rear mech that repeatedly dropped the chain when back pedalling, eventually bending the cage. Replaced with an XT mech that works really well.

A 12 speed SLX is the only mech I’ve done anything like this to. Probably a one off unlucky incident but I was impressed at the damage to so many parts, not so much as a jockey wheel survived

I had no end of issues with poor shifting with one. Then someone posted a link to the Shimano technical manual with a diagram on how to route the cable round the clamp bolt. It’s weird. But problem solved. 

But i can’t find the link now…

My latest GX mech. Both times they have done similar from no discernable knocks

I don’t think there’s much in it with Sram/Shimano when it comes to 12 speed mechs.
I’m currently on 2 of each make that have exploded for no apparent reason.

Prior to 12 speed i really can’t remember me ever having this amount of damage.

Park Tools Dag 2.2 ordered, arriving tomorrow

I had no end of issues with poor shifting with one. Then someone posted a link to the Shimano technical manual with a diagram on how to route the cable round the clamp bolt. It’s weird. But problem solved.

https://si.shimano.com/en/pdfs/dm/MARD001/DM-MARD001-05-ENG.pdf

Re-aligned my hanger last weekend- definitely going to put an alignment tool on my Christmas list, bit of a faff using a spare wheel TBH. I think the B screw adjustment is quite particular with the 12 speed stuff too.

Lifeline alignment gauges are absolutely fine. There’s a grub screw to adjust to take up the slack if needs be. Just give it a slight pull to take up anything more and works perfectly. Mine has been worth it’s weight in gold.

Rubbish…

@shimanomtb 😤

https://www.instagram.com/tv/CfXOOxEDofS/?igshid=ZDBjMWI0ZjMxOQ==

For anyone that doesn’t know – there’s a line on the back of the cage that you align with the 51t cog for b screw adjustment. This is an XT, but same idea…

Cheers all, so I’ve concluded that I’ve either hit it at the end of my last ride or it’s just worn past its acceptable limit. The hanger could be contributing to it, I’ll get a hanger tool.

Checked the set up over, and it had been fine – cable, B-screw, new jockeys all OK. The other thing I didn’t post is that it wasn’t dropping from the biggest cog down the cassette, it would take about 4 clicks before it would jump off, which lead me to changing the cable, and outer.

I’ve finished setting up the GX Mech and swapped the shifter to an NX one I had. It shifts better than ever I think and is silky smooth. Going to keep it as it is and put a new mech on the Aether.

There’s a few things I’ve found that can cause this.

As mentioned above hanger alignment is very important.

B screw adjustment also. Over time the screw can work its way out leaving you with gears that only work at one end of the cassette.

The clutches get sticky. Does it shift properly with the clutch switched off? They can be serviced easily enough and this usually gets them working again for a few hundred miles.

Finally, and I’ve had this on an xt after only 4 or 500 miles – the pivots can wear out so that there’s too much slack in parallelogram for the top jockey to get moved far enough to pull the chain back down the cassette.

I’ve had better luck with deore derailleurs than XT and SLX, I just change the jockeys to XT ones when the originals wear out (this doesn’t take long!)

My new hanger turned up in time for tonight’s ride, the dag turned up a bit later without time to check the alignment.

So I took the old hanger off – side by side the old looked perfect next to the new. However, put the new hanger on and straight away had to readjust everything. Got it indexing perfectly on the stand. Been on a techy, muddy ride and it shifted perfectly throughout the range