Rear Derailleur Installation

[tesseract]

So shifting from big front ring to small causes it? or both ways?

The only connection between front and back is your chain, so logically I reckon it's chain tension?

FWIW when setting my rear mech I checked big front small back for outer limit, and small front big back for inner limit

[Kevy427]

Surely Sickboy should've ordered a new bike by now instead of all this faffing about?

[Bopomofo]

Something wrong with the spring in your rear deraillerueruer?

So, when you move onto the small [inner] chain ring the rear mech is also being pulled inwards. When the chain is on the big ring is there any obvious play in the deraillileilrilerie?

Kev has almost identified the correct solution, but forgot that you should order two new bikes to fix this... roadie and TT.

[JoddyBear]

silly question perhaps, but have you looked at whether the issue is with your chain rather than derailleur?

is the chain old and possibly stretched/worn?
is the chain actually the right length? if its too long the derailleur wont be exerting enough pressure on it when you're making changes and it'll jump around...

on another tack, is the b-limit scew set correctly for the jockey wheels to have the right clearance from the cassette?

or i could just shut up and refer you back to Dave

[SickBoy]

I think most of the parts should be ok, it's a (relatively) new bike and not done too much milage.

It all stems from when the rear derailleurerer cable popped out a while ago - I managed to re-clamp and adjust it no problem, but a while later it started skipping the gear at the back when shifting at the front. I don't tihnk it's taken any knocks that could have caused alignment issues and I think the limit screws etc should be fine - should just be cable tension if I understand correctly.

I've got a few more suggestions to try out, at least it's functional right now...

[SickBoy]

A bit more tweaking cable tension and I've nearly got it - the back is stable now when shifting at the front - I just need more practice I think!