Halfords Hangers

[moman]

Ok, so I bought a replacement hanger for a friends bike. Its a carrera so was no problem getting a hanger to fit.
EXCEPT
I don't think it does?
The bike is rebuilt, RD attached to hanger, shifters work. So I put the chain on to do some final adjustment. Big ring Big sprocket the chain fits but pulls the RD too far forward so when you pedal it pops off onto the 2nd Ring. So small Sprocket, chain is faaaaaaaaaaaar too long and RD needs pulling back to almost the tyre!!
Nothing has been changed on the bike other than the hanger.
Has something been lost from the RD or does chainlength usually get affected buying replacement hangers?
I hate this crap, was supposed to be ridden home friday. pfff.

[moman]

Its a long cage sram x-4

[TrekUk]

Hang on a minute, your posting on WW with a halfords carrera? and dont expect anything to fit from halfrauds.

edit - sram x4 is MTB

I suggest bike radar or pinkbike for this kind of stuff.

[mattyb95]

Is the derailleur b-screw against the notch on the hanger, did you check to see if the hanger was exactly the same as before?

[moman]

Plenty of WW MTBs on here. But this is the only forum I use so apologies for irrelevance. Also this is a friends bike.

Theres a notch on the body that stops the cage swinging too much, I've pushed the cage over this notch and the RD looks in a better shape but that hasn't fixed it either so I put it back.

Bscrew is fully in, limits are fine. Seems to be a common problem with an easy soak and relube fix but I'd already tried that.

[TrekUk]

well how do you expect to turn a £200 tank into a WW machine? also your posting a MTB in the Road section.

[bikerjulio]

Theres a notch on the body that stops the cage swinging too much, I've pushed the cage over this notch and the RD looks in a better shape but that hasn't fixed it either so I put it back.

This quote bothers me. The RD should be first installed with the body swung up (clockwise), and after tightening it will come back to rest on the stop on the hanger.

Next thing to check is hanger alignment, using the proper tool. Something might have got bent.

[mattr]

Did it work before the hanger got trashed?

The bad set up might have something to do with the original failure.