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Discussion Starter · #1 ·
I've come across an issue with a brand new XT 12 Speed derailleur. I installed it last week to replace a working, but beat up, SLX derailleur. It worked perfectly when I installed it and during 3 rides. On my last ride it the shifting was all over the place, so I threw it on the stand to figure it out. I ended up swapping out my entire drivetrain only to discover it was the derailleur, specifically the clutch as it shifts perfectly with the clutch off. So here is what's happening...

I'm going to call it upshifting when shifting to the largest cassette ring and downshifting when shifting towards the smallest cassette ring. Shifting works perfectly when upshifting. When downshifting from the largest ring the derailleur doesn't budge until I get to 5 or 6 clicks, then it grinds the chain/cassette like crazy trying to play catch up. At that point I can downshift and upshift. After upshifting to the largest ring it happens again when I try and downshift. When the derailleur is locked up like this, I grab it with my hand and the knuckle is completely locked up. With enough pressure the lock breaks up and the clutch feels normal. It's like the clutch is sticking and normal downshifting doesn't provide enough force to unstick it, until I've gone through enough clicks to break it free. This happens every time no matter how much or how little adjustment I have at the clutch screw. Turn the clutch off and it shifts like butter.

I've had 11spd forever so I'm very familiar with servicing the clutch and full rebuilds. I've rebuilt a handful of 12spd derailleurs as well. My first thought was to go after the clutch. I cracked her open and everything was clean. I pulled the clutch wheel out and it had the proper amount of grease and was clean. I lubed the crap out of it and put it back no change. I thought about rebuilding it, but it's only been used like 3 times, so I'm trying to send it back.

I should mention this isn't the first one that's done this. My very first XT 12spd did this same thing in short time. It ended up getting destroyed during a ride so I couldn't troubleshoot it. My web searches show some people having some success with the clutch service and others not. My beat up SLX 12spd has not had this issue and neither did an XTR that I mangled way before it's time. Anyone else run into this?
 

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The clutch is either too tight or needs to be lubricated.

It's not uncommon for even brand new Shimano clutches needing to be lubricated.

There are tons of videos out there on how to clean and lube them and adjust clutch tension.
 

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Discussion Starter · #3 ·
The clutch is either too tight or needs to be lubricated.

It's not uncommon for even brand new Shimano clutches needing to be lubricated.

There are tons of videos out there on how to clean and lube them and adjust clutch tension.
I guess you didn't fully read what I posted. I both adjusted the Shimano clutch tension and lubricated it.
 

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I was having a very similar issue. Wouldnt shift down from the largest sprocket unless the clutch was off. With the clutch off it shifted perfectly.

This was my fix. I lubed the clutch first and adjusted clutch tension and was still having the same problem. Next I added a little b screw tension but what i think it really was was the limit screw. I made the L screw tight until it wouldnt shift into the largest ring. then while pedaling i backed it off until it would just make it up and the click at the shifter didnt feel too obstructed by the limit screw. I think my problem was mostly the limit screw which was actually the last thing I thought it was since with the clutch off it shifted amazingly. But now with my limit screw tighter it works as it should. I hope this helps
 

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I can't see how the clutch, which helps keep the chain from slapping around, would affect shifting, especially downshifting to a smaller sprocket. If the clutch was sticking you'd simply have excessive play in the chain as you shifted into the smaller gear set.
 

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I can't see how the clutch, which helps keep the chain from slapping around, would affect shifting, especially downshifting to a smaller sprocket. If the clutch was sticking you'd simply have excessive play in the chain as you shifted into the smaller gear set.
I dont think the clutch is the actual problem but it may add to it. Mine was notchy and rough before I lubed it
 

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Discussion Starter · #8 ·
I can't see how the clutch, which helps keep the chain from slapping around, would affect shifting, especially downshifting to a smaller sprocket. If the clutch was sticking you'd simply have excessive play in the chain as you shifted into the smaller gear set.
As mentioned before I inspected the clutch and lubed it, just like in the videos, using Shimano hub grease as recommended. I've done this many times with my 11 spd derailleurs to get it to shift smoother and to get rid of the dreaded clutch squeak that you get when they get old. Keep in mind there were only 3 rides on this thing in dry conditions. I wish I took a video to show what I'm seeing. It's definitely not normal. I have 3 other bikes with this drivetrain in my household that work fine, so I'm able to use those as a how it's supposed to work.

When the chain is shifted into the largest ring there is no play in the chain it's completely tight. When downshifting the clutch is locking up the knuckle, so the chain remains fully tight despite the lack of cable tension. So, if you click from 2 to 3 to 4 the shifter feels like the cable isn't even attached, it just clicks freely because the cable tension is having no affect on the derailleur att his point. It's when you drop down to 5 or 6 when the cable tension is loose enough for the knuckle to finally break free. When it breaks free the clutch wiggles around like normal and I can shift again. When I go back to the largest gear that chain tension causes the knuckle to lock up again. There is zero movement in the knuckle and takes a good amount wiggling with my hand to break it loose. When I break it loose manually it shifts like it is supposed to.

When working properly in the largest ring the chain is tight, but the knuckle has a small amount of wiggle to it, even with the clutch engaged. This wiggle allows it downshift when the cable tension is reduced. Even with the clutch adjusted to the hardest setting there still is some wiggle in the knuckle at all times. What I'm experiencing is a complete lockup of the knuckle when in the largest ring. I'm assuming it's the clutch that is the problem because it shifts fine with the clutch off. Perhaps there is some other cause inside the derailler that occurs only with the clutch engaged. This is why I'm posting. I did check with my buddy who owns a shop and he says he's seen this a few times and had to do a warranty. So, I'm returning the derailleur at this point.
 

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As mentioned before I inspected the clutch and lubed it, just like in the videos, using Shimano hub grease as recommended. I've done this many times with my 11 spd derailleurs to get it to shift smoother and to get rid of the dreaded clutch squeak that you get when they get old. Keep in mind there were only 3 rides on this thing in dry conditions. I wish I took a video to show what I'm seeing. It's definitely not normal. I have 3 other bikes with this drivetrain in my household that work fine, so I'm able to use those as a how it's supposed to work.

When the chain is shifted into the largest ring there is no play in the chain it's completely tight. When downshifting the clutch is locking up the knuckle, so the chain remains fully tight despite the lack of cable tension. So, if you click from 2 to 3 to 4 the shifter feels like the cable isn't even attached, it just clicks freely because the cable tension is having no affect on the derailleur att his point. It's when you drop down to 5 or 6 when the cable tension is loose enough for the knuckle to finally break free. When it breaks free the clutch wiggles around like normal and I can shift again. When I go back to the largest gear that chain tension causes the knuckle to lock up again. There is zero movement in the knuckle and takes a good amount wiggling with my hand to break it loose. When I break it loose manually it shifts like it is supposed to.

When working properly in the largest ring the chain is tight, but the knuckle has a small amount of wiggle to it, even with the clutch engaged. This wiggle allows it downshift when the cable tension is reduced. Even with the clutch adjusted to the hardest setting there still is some wiggle in the knuckle at all times. What I'm experiencing is a complete lockup of the knuckle when in the largest ring. I'm assuming it's the clutch that is the problem because it shifts fine with the clutch off. Perhaps there is some other cause inside the derailler that occurs only with the clutch engaged. This is why I'm posting. I did check with my buddy who owns a shop and he says he's seen this a few times and had to do a warranty. So, I'm returning the derailleur at this point.
try what i did with the limit screw. oh i also sprayed the heck out of my derailleur with bike protect to give all the pivots on it a light lube

mine was basically doing the same thing. i thought i was going to have to warranty my derailleur also
 

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Discussion Starter · #11 ·
try what i did with the limit screw. oh i also sprayed the heck out of my derailleur with bike protect to give all the pivots on it a light lube

mine was basically doing the same thing. i thought i was going to have to warranty my derailleur also
I did mess around with the limit screw. I had it completely backed off to where it would drop into the cassette and to the point where it wouldn't shift to the biggest ring. I also lubed up all the joints to the point where the entire der was pretty slippery to deal with. At this point I'm done. Thanks for the response though. It's helpful to go through the process.
 

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Discussion Starter · #12 ·
i really didnt think the limit was the issue since everything looked aligned perfectly. no noise. and shifted flawless with the clutch off. but i really think it was mostly the limit
Well you're gonna love this. I figured it out. I inadvertently swapped in a 10-45t cassette when troubleshooting things. I forgot that I even had that thing and it somehow got in the mix. I jammed it side by side with my other bike just now and it stuck right out. That explains everything, except for why my SGS SLX der shifts perfectly with it. Man I burned a lot of time on this.

Thanks all and sorry for waisting your time.
 

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Well you're gonna love this. I figured it out. I inadvertently swapped in a 10-45t cassette when troubleshooting things. I forgot that I even had that thing and it somehow got in the mix. I jammed it side by side with my other bike just now and it stuck right out. That explains everything, except for why my SGS SLX der shifts perfectly with it. Man I burned a lot of time on this.

Thanks all and sorry for waisting your time.
Definitely not a waste of time! It took me forever to figure mine out too and I gave up on it actually for a while.

What did it end up being?
 

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Discussion Starter · #14 ·
Definitely not a waste of time! It took me forever to figure mine out too and I gave up on it actually for a while.

What did it end up being?
Well, I'm pretty sure it was because I had the wrong cassette installed (10x45t instead of 10x51t). I was tired and had some beers in me when I began troubleshooting. The cassette was the first thing I swapped, then the shifter/cable, then focus on the derailleur. Unfortunately, I already returned the XT derailleur so I wasn't able to test that theory. Bike is shifting great with my old SLX der and the proper cassette so I'm going to leave it alone for now.
 

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This makes sense now. Clutch on, chain tight, B tension so close that the chain can't move to the next gear. Bet if you backed off the B screw it would have shifted.
 
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