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Shimano 12 speed shifting issues

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Shimano 12 speed shifting issues

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flag Branmuffin
O+
Posted: Jun 5, 2020 at 6:12 Quote
I upgraded to 12 speed Shimano (xt) last season and have put around 1,000 miles on the drivetrain. Everything has been very smooth but just the last couple weeks I have been running into an issue I cannot get squared away.

Shifting has a tad bit of hesitation on the 4th highest gear, or around the 4th lowest. I just can’t get it perfect through the whole cassette. Adjusting tension seems to move the issue from either the 4th or to the 8th gear.

I have replaced all housing and cable.
Replaced deraileur hanger
Disassembled the rear mech, cleaned and greased, serviced the clutch per Shimano manual and set appropriate clutch tension (4ish NM). Cleaned pulleys and torqued.

I have gone through the set up and adjusted limits, b tension and everything should be correct but the small amount of sloppy shifting remains.
The most puzzling part of this issue is it shifts best with less cable tension. When I tension the cable to the mech, it shifts best with 0 turns on the shifter barrel adjuster. If I add 1-2 clicks of adjustment, it will instantly start hopping gears, even with 0 clicks the cable tension seems too high.

My only remaining thought at this point is my chain could be worn enough to cause the issue. I have a chain gauge but it’s only for .75 or 1.0 wear, which it does not meet. I will pick up a new gauge with a .50 measurement today and a new chain to test but wondering if there’s another glaring issue I could be missing?

Thanks for the help.
flag Reaperactual
Posted: Jun 5, 2020 at 7:19 Quote
Could be a stiff link/s on the chain? Maybe your trouble cogs have some amount of wear?

For fixing the 0 clicks issue undo cable from anchor bolt, rotate the fine tune barrel adjuster one full rotation anti clockwise, re-thread cable into anchor bolt making sure to route and fix in correct place, then you will have clockwise and anti clockwise fine tune adjustability.
flag Branmuffin
O+
Posted: Jun 5, 2020 at 7:22 Quote
Reaperactual wrote:
Could be a stiff link on the chain. For fixing the 0 clicks issue undo cable from anchor bolt, rotate the fine tune barrel adjuster one full rotation anti clockwise, re-thread cable into anchor bolt making sure to route and fix in correct place, then you will have clockwise and anti clockwise fine tune adjustability.

I did try this and even adding 1-2 clicks and reattaching the cable, then backing off the barrel adjuster the mech still wants to act like there is too much cable tension.

Quite strange, I am at a loss on this one.
flag Reaperactual
Posted: Jun 5, 2020 at 7:25 Quote
Mech hangar straight, as in fitted properly and tight?
flag Branmuffin
O+
Posted: Jun 5, 2020 at 7:44 Quote
Reaperactual wrote:
Mech hangar straight, as in fitted properly and tight?

Yep, even threw a new one on just to be sure and same issue.
flag Reaperactual
Posted: Jun 5, 2020 at 8:03 Quote
Have you serviced the jockey wheels with derailleur strip down? Top Jockey wheel still have the lateral 'free float' movement?

After that I suppose your chain or whole drivetrain has worn out which would explain sloppy shifting not bad going to get 1000 miles before issues?
flag Branmuffin
O+
Posted: Jun 5, 2020 at 8:14 Quote
Reaperactual wrote:
Have you serviced the jockey wheels with derailleur strip down? Top Jockey wheel still have the lateral 'free float' movement?

After that I suppose your chain or whole drivetrain has worn out which would explain sloppy shifting not bad going to get 1000 miles before issues?

There’s really no float on the jockey wheels but I don’t think there is supposed to be on the 12 speed stuff, at least not as much as on the 11speed. They were cleaned and torqued to 3nm as the dealer manual shows.

1000 miles is pretty low mileage for the life of a drivetrain IMO. I highly doubt the chain is worn to .5 percent yet but I will find out shortly once my shop opens. Cassette is clean, don’t see anything worn excessively, I will probably pull it just to take a look. And no stiff links on the chain that I have noticed.
flag Reaperactual
Posted: Jun 5, 2020 at 8:25 Quote
Sorry Pal, no experience of 12 speed and XT stuff. Can't think of any other things that you haven't already checked. Good luck sorting out the problem. Smile
flag slomtbr
Posted: Jun 5, 2020 at 8:42 Quote
Even though the hanger is new and straight, it may not be aligned to the rest of the drivetrain.
flag mattbrown9
O+
Posted: Jun 5, 2020 at 8:45 Quote
Someone might have just beat me to this - but new hanger doesn't equal straight hanger. You need to align a new hanger after install on a frame. I don't have a ton of 12sp shimano experience - but hanger alignment is critical for 12sp eagle stuff also, I can't imagine it's much different.
flag jimsutty
Posted: Jun 5, 2020 at 8:58 Quote
Is the pulley set in the correct order (guide top, tension lower) and are both bushings present and in good order?

I'd have that inner cable straight out - might have unravelled or have minor corrosion if the coating has degraded. Replace, preferably with a new outer or do your best to flush the line through top to bottom gravity fed and lube before inserting the new cable.

Have you had the shifter apart and watched it move through its shifting pattern - check the shifter is configured correctly.

You say your having issues in the middle - inspect those cogs for any cracks. My highest cog once split and would only offset under load.

Was there any change when you serviced your clutch?

If the rear mech and hangar bolts are secure then gently apply pressure to the hangar both ways when shifting and observe what happens.
flag Branmuffin
O+
Posted: Jun 5, 2020 at 13:34 Quote
Thanks for the suggestions. I took it down to the LBS and he seemed to think the tension was too high as well and slowly fed the mech a hair of slack and kept adjusting until everything was shifting clean. I had tried this but clearly my adjustments were too large.

I originally put this drivetrain on my Jeffsy and the setup was nearly identical to the Shimano manual of adding 5 clicks of barrel adjuster to get that sweet spot in the tension. For whatever reason that isn’t the case on my Ripmo but glad it’s sorted and I can go sweat my ass off riding today.
flag Branmuffin
O+
Posted: Jul 9, 2020 at 9:01 Quote
Branmuffin wrote:
Thanks for the suggestions. I took it down to the LBS and he seemed to think the tension was too high as well and slowly fed the mech a hair of slack and kept adjusting until everything was shifting clean. I had tried this but clearly my adjustments were too large.

I originally put this drivetrain on my Jeffsy and the setup was nearly identical to the Shimano manual of adding 5 clicks of barrel adjuster to get that sweet spot in the tension. For whatever reason that isn’t the case on my Ripmo but glad it’s sorted and I can go sweat my ass off riding today.

Ok, revising this as after a few rides the shifting issues slowly came back but it is now resolved. The shop got it shifting pretty clean just off tension alone but once on a steep climb some of the janky shifting returned, especially noted when I cranked up the tension in the clutch. So, I replaced the chain with a new Deore 12sp chain. Same problem, a little sloppy shifting most noticeable between the 3-4th smallest cog. Last ditch effort before I bought a new cassette, I pulled it from the wheel and I believe one of the spacers was on the wrong side of the cog, which would explain the shifting issues in that specific spot in the cassette. I have about 15 rides since and shifting has been 100% flawless. I believe the reason I was also having issues in the 7-8-9 range was due to too much tension to get the 3-4 gear shifting clean that it was causing issues in the lower gear range.
Anyways, I had put the cassette on a new wheel set right about the time this became an issue so I think my theory is pretty sound. Most are probably smart enough to get the spacers in the right place, but it’s worth checking if you have similar symptoms.
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