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- New jockey wheels correctly installed
- Chain, cassette, ring 80km old
- New cable and outer
- Outers cut square and not compressed
- Upper and lower limits set right
- Cable clamped correctly
- Hanger checked and tweaked with park hanger alignment tool
- B tension perfect for 51t
- Chain length right
Bike in as jockey wheel (top) split after a ride, also cage scraped as opposed to banged.
Can get first 4 cogs indexed perfectly, then as it moves into the bigger cogs it's scraping. Same symptom as a bent hanger.
If I get the biggest 7 indexed perfectly then it jumps around on the smaller 4
The spacers are arranged right before that assumption is made.
12 speed microspline.
The split jockey wheel I assume as rotated the cage slightly and messed up the mech as it extends, have I missed anything??
When you say you splint a jockey wheel, what do you mean and how did you do it? I still reckon your hanger is a bit bent, is the wheel you're aligning it against totally true?
I always use the valve as the constant so yes it's perfect, brand new wheel also.
Valve left horizontal
Valve right horizontal
Valve top vertical
Valve bottom vertical
Valve left horizontal
Valve right horizontal
Valve top vertical
Valve bottom vertical
Do you also check alignment at NW / SE and SW / NE axes? (Not sure whether you're meant to, but I couldn't get it right on my gravel bike until I'd checked and adjusted hangar alignment in those directions as well.)
If that all adds up, my guess is on a bent cage?
have I missed anything??
Chain line issues?
Definitely routed the inner cable correctly from where it enters the mech to the clamp? This is easy to mess up as it goes in the opposite direction to what you'd expect?
I suspect the mech might be bent if the hanger is perfect and the cassette is correctly mounted and torqued on the hub. Unless the chain line is awful.
I’m having fun and games with my Shimano 12 speed at the moment, with the clutch on the mech won’t shift out of the 51t down the block but shifts with it off. Just about to change cassette / chain / chainring in one go and give it a good setup from scratch
Have a read of this review from BikeRadar. He mentions having to adjust the b screw contrary to Shimano recommendations.
FWIW I have got 2x Deore 12 speed and they are both super smooth
That's my deduction, bike is an 80km old rocky mountain slayer, new pro5 hubs, new xt/slx drivetrain
Only issue it had was the split jockey wheel prior to the owner bringing in.
@cerrado-tu-ruido fitted loads of these as per shimano instructions and all sweet as
Had this on my new this year bike (so all drivetrain new) with 12 speed Shimano SLX...short answer was it was a very slightly bent mech hangar. Spent an age messing with indexing and b-tension but big clue really was that it went from perfect indexing to fubar at the end of descent.
Concerned me that it was that easy to bend the mech hangar (is an xc bike), how little it was bent and the fact i wasn't even conscious of banging it (no damage to mech...not even a scratch)
Other aspect i have which i haven't had with my sram 12 speed is that the chain dismounts from the top jockey and gets wedged between mech cage & side of jockey wheel...rather random when it occurs too
SLX rear mech? - I have found a couple of these bend at the cage quite easily - looks like the alloy cage can flex (sometimes causing chain to jump off top jockey scoring cage). My fix was to fit a Deore steel cage and not had problems since
Xt
Is the cable tension set right? I find i need to tweak the tension on the barrel adjuster to get it right. There doesn't seem to be a right way to do it, just trial and error, but suddenly it will work.
I've had similar issues with an XT mech.
After a rock in the wheel ripping a spoke out incident.
Went from working fine to only being able to set it up for either the top or bottom half of the cassette working.
Checked gear hanger for alignment and everything else was perfect.
Tried straightening the mech out just a fraction and it snapped at the composit knuckle.
Before it snapped I compared it to a new mech and it didn't look any different.
Fitted a new mech and it worked perfectly.
That's the second XT mech I've had that's snapped in the same place.
@bikerevivesheffield that sounds like a bent rear mech.
@joebristol it will be this pin causing your issue, not the side with the clutch, but the side into the mech body gets dry, corroded and sticky.
https://nsmb.com/articles/shimano-derailleur-clutch-service/
@jimmy748 @bikerevivesheffield
It’s only a month or two since I dismantled the cage and cleaned out / greased the pivot so I’m hoping it’s not that again already.
I don’t have to do anything with the GX eagle mech on my other bike - it just keeps working. Shimano is annoying me at the moment!
Is the chain installed the correct way? (Shimano logo facing out).
There is the issue ☝️
New one ☝️👍
What’s the issue - bent / twisted cage? I think as standard there is a bend to the cage so it’s hard to tell what’s right and what’s broken.
That top jockey wheel does look a funny angle though.
edit - just seen the extra photo - old cage wasn’t looking too good vs new one.