Help me understand 'B' adjustment on SLX rear mech

101_North

Folks,

After a few shifting issues and chain slipping issues recently I've been tinkering with my rear mech. Can anyone explain the 'B' screw adjustement because as far as I can see it does nothing.

If you look at the following picture:

http://www.woollyhatshop.com/images/upl ... r_mech.jpg

Is the mech meant to pivot around the torx bolt which is above the 'B' screw? I've taken the mech off and it certainly looks like it's meant to. In fact theres a tab on the back which looks like it should move the body around this pivot as you turn the 'B' screw. This joint is solid in my mech and does not rotate - in fact the 'B' screw doesn't seem to contact anything except fresh air so I'm guessing something is up. I've tried to free the torx bolt but it's stuck tight.

Any info would be great.

101

Chunkers1980

WHat mech have you got? (guessing a Shadow type)

THat sets the angle of the top jockey to the cassette. 5-6 mm IIRC below the engaged cog. THe closer you get it the quicker and more solid a gear change will be.

Chunkers1980

Once the mech is tightened to the hanger that bolt act as a pivot for the mech.

nicklouse

pics of your mech and we may beable to advise what is wrong.

as above the B screw adjusts the position of the top jockey wheel.

101_North

That's what I suspected but it's stuck tight - won't budge - and I suspect never has. I think this could be the reason for my almost continual shifting issues and the fact that I go through chains and cassettes like they're made of soft stuff. Now that I think of it my mech always sat at a funny angle compared to photos of bikes with the same mech and I suspect my LBS didn't fit it right.

I can try looseing that torx again but I was giving it some serious welly earlier and couldn't shift it. I guess I could better position the mech by loosening the mech hanger bolt, moving the mech and tightening. If that pivot is stuck fast that's maybe the best I can hope for!

Found another thread and it sounds like the same issue:

viewtopic.php?t=12852382&p=17600841

101

101_North

@nicklouse I'll try and get photos tonight. Cheers

101

Chunkers1980

Someone else was having trouble with this in another thread. If the mech is off, the attchment bolt should just flop from side to side with little or no friction. Is there a circlip on the back to remove? Shimano don't list a part number for it, so I think they've made it to not be able to come off.

101_North

There is a circlip. Popped it off and the thing still won't budge. There is no movement around that pivot/bolt. I'll try again tonight. At least I know it should move - otherwise the 'B' adjustment screw is pointless!

Thanks for the help. I'll post back if I get anywhere.

101

supersonic

Put the rear grear into the largest cog - how close is the jockey wheel to the cog?

101_North

It's off the bike but it was a mile off when it was still on the bike. In fact if I was in large/large (just trying it out when working on the bike - never actually use it) the chain doesn't contact the upper jockey wheel at all.

Sounds like I should be sweet if I can get movement around that pivot.

Thanks folks

101

supersonic

The B screw may be siezed in - I'd try some dismantling fluid like Plus Gas.

101_North

The B screw moves fine just doesn't engage anything due to their being no movement around that pivot. The 'B' screw only contacts the 'arm' when it's fully screwed in so the bits obviously stuck at one extreme of it's movement.

Cheers

101

supersonic

Ah I see!

101_North

After much swearing and more than a little force I managed to free the torx bolt. The whole thing had that much red threadlock on it that it was stuck solid. To be honest I've no idea how the thing managed to shift at all. It's clearly never been right and hopefully explains why my chains and cassettes get eaten so quickly!

Anyway. 5 minutes of setting up and it's shifting as sweet as a nut.

Thanks for all the help folks

101

wakou

Chapeau to that man..