rear derailer grinding on back gears

"-" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

Hi all,

I've got a shimano sora gear set, giant ocr4. Heres a picture of a rear
derailer for reference

http://www.abc-of-mountainbiking.com/images/pics/rear-derailleur.jpg

The top cog (jockey pulley) on the rear derailer is grinding on some
gears. The equilibruim position of the jockey pulley is too far
counterclockwise and this causes the problem. The derailer is attached
through the wheel bolt and I cant simply twist the whole thing relative
to the frame as it fits in snugly.

Any Ideas? tighten the chain by removing links? perhaps try adjust the
internal spring with an allen key? (would be top allen key fitting in
this picture http://www.precisiontandems.com/cat_pics/rdultegratrip10.jpg)

Thanks for the help.
Richard

It might need a tweak on the B adjuster screw.

http://sheldonbrown.com/derailer-adjustment.html#rear

cheers
Jon_H

Thanks for the suggestion, but I've tried that, the b adjuster screw
seems to adjust the "end stop" for the derailer when it is fully twisted
around clockwise.. the derailer atm is too far anticlockwise when in
equilibrium with the internal spring of the derailer and the chain tension

Jon_H said:

"-" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

Hi all,

I've got a shimano sora gear set, giant ocr4. Heres a picture of a rear
derailer for reference

http://www.abc-of-mountainbiking.com/images/pics/rear-derailleur.jpg

The top cog (jockey pulley) on the rear derailer is grinding on some
gears. The equilibruim position of the jockey pulley is too far
counterclockwise and this causes the problem. The derailer is attached
through the wheel bolt and I cant simply twist the whole thing relative
to the frame as it fits in snugly.

Any Ideas? tighten the chain by removing links? perhaps try adjust the
internal spring with an allen key? (would be top allen key fitting in
this picture http://www.precisiontandems.com/cat_pics/rdultegratrip10.jpg)

Thanks for the help.
Richard

It might need a tweak on the B adjuster screw.

http://sheldonbrown.com/derailer-adjustment.html#rear

cheers
Jon_H

Apart from the possibilities of the mech not being suitable and
something being bent could your chain be the wrong length ? That is
does the problem only exist using one of the front rings ? Easy enough
to fix.

Jon

- said:

Thanks for the suggestion, but I've tried that, the b adjuster screw
seems to adjust the "end stop" for the derailer when it is fully
twisted around clockwise.. the derailer atm is too far anticlockwise
when in equilibrium with the internal spring of the derailer and the
chain tension

I don't understand that because tightening the "b" screw should do what
you want. By anticlockwise, I take it you mean when looking from the
right-hand side of the bike. I also take it that the problem is worse
when in bottom gear (smallest chainring + largest rear sprocket). Please
explain the problem using other words if it's worse in other gears
(because I might be misunderstanding what the problem is in that case).

If the chain is longer than necessary for the combination of largest
chainring and largest rear sprocket, you may be able to remove a link or
two, which should help.

Failing all that, try a longer screw if that would make any difference.

The business about the derailleur being "attached through the wheel bolt"
might be relevant as well. Maybe a different derailleur with an adapter
would be better -- an adapter that allows a modern derailleur to be
attached to an old frame without a derailleur hanger.

~PB

"-" <[email hidden]> wrote in message news:[email hidden]...

Quoted message said:

Hi all,

I've got a shimano sora gear set, giant ocr4. Heres a picture of a rear
derailer for reference

http://www.abc-of-mountainbiking.com/images/pics/rear-derailleur.jpg

The top cog (jockey pulley) on the rear derailer is grinding on some
gears. The equilibruim position of the jockey pulley is too far
counterclockwise and this causes the problem. The derailer is attached
through the wheel bolt and I cant simply twist the whole thing relative
to the frame as it fits in snugly.

By which I take it you mean the derailler is screwed into a slotted
plate which then slots on the axle and is tightened with the wheel nut,
as in the old days before gear hangers ?

If you loosen the allen bolt which attaches the derailler body
to the slotted plate, you should be able to change the angle of
the derailler that way and maybe solve the problem.

michael adams

....

Quoted message said:

Richard