Chorus Rear Mech Adjustment

beancounter

I should know this by now....

Anyway, just built up a bike with a Chorus 10 speed rear mech. All is well except I can't get the mech to complete the shift to the largest sprocket. It goes on to the sprocket but won't stay there. Slackening off the limit screw doesn't make any difference. Adding cable tension doesn't make any difference.

What else can I try?

Thank you

bc

keef66

Is the mech hanger straight?? Ditto the frame??

Failing that, are you lacking a spacer behind the cassette?

Monty Dog

Also check:

Is chain correct length?
Is cable outer to rear mech too short?
Is the inner cable clamped correctly?

beancounter

All parts have been transferred from another frame and worked fine before, howver in answer to possibilities so far:-

1. mech hanger looks straight to me
2. I hope the frame is straight but it's not new so....
3. there's no spacer behind the largest sprocket, never has been
4. would a slightly too short chain cause this? it could be alink or two less than ideal
5. cable outer seems fine, all other shifts ok
6. cable is clamped correctly

bc

stevec205gti

And double check you're adjusting the correct limit screw

on-yer-bike

beancounter wrote:

1. mech hanger looks straight to me


bc

It may 'look' straight but you still need to check its alignment. Brand new hangers still have to be bent slightly to fit the frame.

onbike 1939

beancounter wrote:

All parts have been transferred from another frame and worked fine before, howver in answer to possibilities so far:-

1. mech hanger looks straight to me
2. I hope the frame is straight but it's not new so....
3. there's no spacer behind the largest sprocket, never has been
4. would a slightly too short chain cause this? it could be alink or two less than ideal
5. cable outer seems fine, all other shifts ok
6. cable is clamped correctly

bc

This could be the problem and it would be as well to lube the pivots on the RD as winter gunk can mean that this does not travel the whole of its arc.

beancounter

So just out of curiosity I wound on a lot more cable tension - 3 or 4 full turns of the adjuster. Lo and behold, chain now goes on to largest sprocket and stays there.

But, changing back up through the gears I now can't get to the smallest sprocket - my final click of the shifter only gets me to the second smallest sprocket.

It's like the 10 speed shifters have lost a speed.

I'll just slink off to the LBS next week, Alan'll sort me out (again).............

bc