This is two bits not one, right?

[swee'pea99]

I decided to finally take the plunge and try to sort out my old Shimano 600 rear mech. I'm trying to make the slight adjustments with the barrel-adjuster, but it's not going that brilliantly. I think it might be something to do with this part here:

If I'm reading it right, the right-hand one of the two milled sections - ie, this feller here:

should move independently of the other, allowing me to adjust the cable-tension by varying the gap (currently zero) between the two. Is that basically correct? Or is there another reason I just cannot get it to turn. Basically, is it just that it hasn't been adjusted in 20+ years so it's got a bit seized up, or am I trying to unscrew two parts that are actually part of the same thing, and don't turn independently at all?

 

[C R]

It is hard to tell, but I think I can see metal joining both knurled sections, so I would say it is one part.

 

[matticus]

ONE part - the WHOLE THING turns in the derailleur body (IIRC). This movement (screw in/out of body) changes the cable tension.
It's pretty much that simple :-)

 

[Specialeyes]

It's all one piece. There should also be a spring and an adjuster nut between the knurled end of the part you have here and the body of the derailleur and, depending on the mech it may have 4 steps on the back of it so you're limited to quarter-turn adjustments. The flat on the barrel there is to stop the whole thing turning when you turn the adjuster nut.

Edited to add: like this!

 

[PeteXXX]

Is it just a weight saving groove?
¼ gram here, ¼ gram there. It all adds up, you know..

 

[swee'pea99]

Fantastic! Thanks all. Forgive me, one more? If you have a mo...?

The reason I started fiddling with it was because, having recently fitted a new cassette & chain, I was getting a rather odd chattering noise in certain gears - basically, when I was on the small ring at the front and shifted up to the smaller sprockets at the back. I've now identified the source of the chattering. This is how the mech sits when in that sort of combination:

...and it's here that the 'chattering' occurs:

The noise being the links clipping that chain-guide tab as they go by. I was just wondering, should I try taking out a couple of links from the chain? It seems to me that the mech is 'going too far back', as it were, and needs the chain to restrain it slightly. Does that make sense/sound right? (I've tried the 'verbotten' combination of big front ring + biggest rear sprocket, and there's still some slack in the system, to the extent that it at least feels as though I could take out a link or two without causing any kind of seizure.)

Thanks again...and in anticipation.

 

[raggydoll]

Does look like the chain is too long.

I take it there was no rubbing issues with the old chain?
If so, can you count the links on your old chain and on your new chain?

Whenever I fit a new chain I just count the links on the old one and cut the new one to the same size.

 

[T4tomo]

Fantastic! Thanks all. Forgive me, one more? If you have a mo...?

The reason I started fiddling with it was because, having recently fitted a new cassette & chain, I was getting a rather odd chattering noise in certain gears - basically, when I was on the small ring at the front and shifted up to the smaller sprockets at the back. I've now identified the source of the chattering. This is how the mech sits when in that sort of combination:

View attachment 596805

...and it's here that the 'chattering' occurs:

View attachment 596806

The noise being the links clipping that chain-guide tab as they go by. I was just wondering, should I try taking out a couple of links from the chain? It seems to me that the mech is 'going too far back', as it were, and needs the chain to restrain it slightly. Does that make sense/sound right? (I've tried the 'verbotten' combination of big front ring + biggest rear sprocket, and there's still some slack in the system, to the extent that it at least feels as though I could take out a link or two without causing any kind of seizure.)

Thanks again...and in anticipation.

Yes take a pair of links out. Bizarrely I had exactly the same issue with a similar 600 rear mech on a bike I've just bought. i tried it in small small and in Big big before I took the old chain off and realise it was a tad too long and rubbing like yours, so split the new chain 2 links shorter.
and clean your jockey wheels

Whenever I fit a new chain I just count the links on the old one and cut the new one to the same size.

this only works if you don't have any issues pre changing the chain, but it is a good rule of thumb. Just be wary when inheriting a bike!

 

[swee'pea99]

Does look like the chain is too long.

I take it there was no rubbing issues with the old chain?
If so, can you count the links on your old chain and on your new chain?

Whenever I fit a new chain I just count the links on the old one and cut the new one to the same size.

My thinking too. I did that - the new chain's the same length as the old one.

I didn't really have chattering with the old chain, but I think that may be because I never used the smaller sprockets on the old cassette - which is why I swapped out the cassette in the first place, having decided it was a bit daft to have a cassette with a range wider than I needed, with big 'gaps' between gears. The new cassette has a smaller range, with smaller increments between the sprockets - which works very well, and has delivered just what I was after, in terms of smoother changes up & down the run - but I suspect I'm still using a chain length originally dictated by the old 28-tooth older sprocket, when I only really need it long enough to cope with a 25-tooth.

 

[swee'pea99]

clean your jockey wheels

How very dare you! I just cleaned them!

 

[swee'pea99]

(Otherwise many thanks, and I think I'm going to go ahead...)

 

[raggydoll]

My thinking too. I did that - the new chain's the same length as the old one.

I didn't really have chattering with the old chain, but I think that may be because I never used the smaller sprockets on the old cassette - which is why I swapped out the cassette in the first place, having decided it was a bit daft to have a cassette with a range wider than I needed, with big 'gaps' between gears. The new cassette has a smaller range, with smaller increments between the sprockets - which works very well, and has delivered just what I was after, in terms of smoother changes up & down the run - but I suspect I'm still using a chain length originally dictated by the old 28-tooth older sprocket, when I only really need it long enough to cope with a 25-tooth.

Sounds like that's what it could be.
Either, way, slightly shortening should hopefully do the trick.

Always a bit scary shortening a chain in case it is too short!

 

[T4tomo]

How very dare you! I just cleaned them!

Are you sure? I've seen cleaner free range pigs

 

[swee'pea99]

Are you sure? I've seen cleaner free range pigs
View attachment 596824

You should've seen it before

I thought the screwdriver was going to bend

 

[swee'pea99]

I've done the deed, and it seems to be all good! Trial ride shortly, but certainly up on the stand all seems to be well - the chain's no longer hitting the tab. I still haven't quite got the gears adjusted properly - apparently there's a YT vid I should watch...any suggestions welcome. Meantime, here we go for what it's worth...