I'm trying to adjust my rear derailer. I have Gripshifts and a Shimano
Derailer (Not Rapid Rise type). The derailer shifts at the correct
position of the shifter and after it has shifted the chain runs
normally. However, in the middle of a shift the derailer will make a
prolonged crunching sound.
The sound is caused by the chain being jammed between the jockey wheel
and the sprocket it's meant to be shifting to. The jockey wheel isn't
actually touching the sprocket, but pulling the chain at such an angle
that it's jamming. The chain on top of the sprocket is still engaged,
so the sprocket still turns, but the lower chain gets pulled along the
flat side of the sprocket instead of around the outside. Eventually,
one of the teeth will engage and this link will pull the lower chain
with it, but this leaves un-engaged chain on the sprocket, which takes
a revolution to sort itself out. This problem is barely noticeable
between sprockets one and two, but gets worse as they get larger.
I do not think this is caused by too short a chain, because the
problem is present in all front gears. I have tried adjusting the
B-screw and it didn't seem to help. The problem is not cause by the
shifter cables because the derailer displays the same behaviour when
moved manually. However, the only thing that seems to help is
loosening the cable tension until the derailleur only just shifts.
Any ideas?
Thanks for any help,
Steff