Hi all. I have a problem.  12 speed eagle gx. I can shift all the way up to easier gear, but then the rear mech gets stuck and won’t shift down.

Picture the scene… I use the 50 cog to tackle a steep climb, get to the top where it is flat and want to shift down and the mech just stays there. The shifter releases cable though.

I have change the gear outer, new inner cable, but it still happens.Seems to be fine in the stand but not when bike is weighted. Chain too short maybe? There are no unusual kinks, everything seems smooth.

On a separate but perhaps related note, the chain sometimes comes of the top jockey wheel and gets wedged between the backing plate and the jockey. This happened last year and led to an exploded rear mech. Replaced the mech and it seems to be happening again…

Have you changed the inner and outer at the same time – sounds like there is too much friction in the cable.

Did you set B-tension with the SRAM tool? They recommend setting it under sag too

On the first one have you used the plastic tool to set the B screw with the suspension saged?

Re the falling off the jockeys. I had the same it got worse until I got a new mech

About the jockey wheel problem, it seems to be as they wear, they develop side-to-side play, and the chain can come off and get stuck as you describe. I presume it happens in smallest sprocket? Replacing the jockey wheels will fix it, but not for very long. It’s not a problem I’ve had with other mechs but seems common with GX. I changed to Shimano for this reason.

My money is on worn jockey wheels, the OE ones are a bit crap to be honest and get very sloppy over time. My X01 mech was playing silly buggers so I got some new Hope ones, as that’s all I could find and they were marginally more expensive than the plastic SRAM ones.

I had this with the jockey wheels
I tried aftermarket etc etc.. no joy still the same SRAM issues
I think I did a few things, I took an adjustable spanner to the cage and bent it around so that there was less gap, possibly it had got damaged.. and totally reset up the tension limits etc from scratch and I think it was OK.. I then decided the clutch tension on a GX mech was rubbish and fitted a Deore instead

Gear outer and inner replaced at same time.

My mistake but it originally was a gx eagle mech, that exploded so replaced with an XT

Ah if it’s an XT 12 speed I’m guessing you’ll need to service the clutch (easy test is to turn the clutch off and see if shifting is better). Turn the clutch off, undo the 3x2mm hex bolts that hold the cover on, take photos of how the clutch is installed, ease the mechanism out (might be a bit stiff if it’s gunged up), clean carefully avoiding any messing with the inside of the roller bit, apply a light grease avoiding the flat faces of the roller bit (I use DT grease which seems OK), put it back in how it was paying attention to which way round the cam sits (refer to photos if in any doubt), replace cover (tiny bit of grease on the gasket will hold it in place), turn clutch on and adjust (2mm hex under rubber cover on clutch) so there’s not quite enough tension to hold the mech in place when you change down the block (ie wind tension up a bit, stick it in 50t then change down, mech will stay put so then release tension until mech springs back).

Probably 10 mins job once you’re familiar with it – and it’ll need doing whenever the clutch starts sticking again. No idea what they did differently for the 12sp clutch but I have an 11sp that’s never been touched and still works fine, the 12sp is much more of a diva.

Picture the scene… I use the 50 cog to tackle a steep climb, get to the top where it is flat and want to shift down and the mech just stays there. The shifter releases cable though.

Is the mech moving at all when you shift to the harder gear and does it shift if you click multiple gears?

If you disconnect the cable and move the derailleur by hand (while rotating the cranks) does it do the same thing? If not, it sounds like it may be an indexing or hanger alignment issue.

Worn jockey wheels and or cassette.

Not dropping down is IME a symptom of a worn cassette.

Dropping off the jockeys is par for the course of knackered jockeys.

Sram go at the bearings but look fine. Shimano bearings last but turn to ninja stars in a similar time frame.

B-tension is most likely cause of this.

Even with baggy jockey wheels, if the B-tension is set correctly theres enough space under the sprocket for the chain to deflect.

Yes the mech moves, the wire goes slack, but it doesn’t drop… Cassette isn’t too old and I only really ride park haha it’s true, I rarely use the big ring… Everything is used but not worn out. I’m guessing b tension is the cause, which tbh is something I’ve long struggled with on the bike. Banshee titan if interested.

Would eagle axs solve is? 😃

Have you checked alignment of rear mech?

I have yes. I replaced the rear mech hanger.

Too much b tension or too little what’s the bet?

howsyourdad1

Would eagle axs solve is? 😃

Eagle AXS would come with the wee SRAM tool for setting B-tension – cheaper to get just the tool, though

But I won’t criticise anyone for a cheeky upgrade

Ok, getting closer. Have checked the mech, b screw etc. It seems to be clutch related. Clutch off, the shifting works great. Clutch on , the problem resurfaces. It appears the clutch is not letting the mech drop back down, it is ‘keeping’ the tension. So what to do? Service the clutch? Back it off a quarter of a turn?

 Service the clutch?

This, it’s pretty easy.

@thepurist good stuff him/her

Not just the clutch though, you need to remove the little axle behind the clutch and give that a clean and grease as well.

Is your chain long enough? A slightly too short chain will mean it gets stuck on the biggest cog

All done, was the clutch. Gave it a clean and mini grease. Also found that it was wound in as far as it could go so backed it off a little. Thanks all !  Alas no AXS upgrade for the time being 🙂