Rear derallier mech

[Tom]

Can any on assist please
I have been trying to set my nine speed rear mech.
How ever well I try to set my cassette up to change sprocket the chain does not change cleanly.
My mech is a Shimamo
RD 770 and has some little sideways wear, if it is time to replace it what is the modern equivalent.

[Brucey]

before condemning the mech, be sure that it isn't a bad cable.

How do you do this? Well it is easiest just to replace the cable; if the cable is old it is probably in need of replacement anyway.

Also be sure that it isn't wear in the jockey pulleys; these can be replaced quite cheaply.

And check that the gear hanger alignment is correct (this can easily result in iffy shifting)

Finally be aware that worn chains and sprockets don't shift well either, and they might well be overdue for replacement too.

If you do need to replace the RD then any shimano 9s mech (with the correct capacity) will work.

cheers

[Tom]

Thank you for a prompt and constructive reply,

Tom

[Tom]

sorry,
have done all, except the gear hanger, how do you accomplish that please

[Brucey]

use gear hanger alignment tool. See park tool blog for details.

An alternative is to use a nutted rear wheel with a 10x1 threaded spindle in place of the tool.

cheers

[pwu]

M770 is rapid rise...

[Brucey]

good point. However there is no 'modern equivalent' to a rapid rise mech. Also we don't know if it is matching rapid rise shifter or not...?

If 'not' then this could be what is causing the problem?

[edit; shifter SL-M770 is listed as compatible with RD-M770 (rapid rise) and RD-M771, M772 (top normal) mechs, so the nature of the shifter per se probably isn't the issue]

cheers