Shimano 105 rear mech adjustment

shinsplint

Quick fix needed tonight, and hoping you guys can help.

On my last ride (when I punctured), the bike blew over and I think my rear derailleur has been knocked. I now find that if I change down as far as possible the chain gets thrown into the wheel. I can shift up and down no problem, so I think I just need to adjust one of the limiter screws. Any idea which one? And which way to turn?

Thanks in advance.

sungod

the rear mech is bolted to the rear hanger, the hanger needs to be parallel to the plane of the wheel for correct shifting

it's very likely that your rear hanger is now bent and needs re-aligning (if it's badly bent it may need replacing)

you can get an alignment tool, or borrow one, or try one of the diy methods, or go to the lbs and ask them to do it

to adjust the rear mech itself, full instructions are on...

http://techdocs.shimano.com

shinsplint

Cheers sungod

nicklouse

as above bent mech hanger.

have a read of the info on Parktools.

onbike 1939

If the hanger is bent then it all depends which type you have. On some bikes the hanger is part of the frame while on others the hanger consists of a replaceable aluminium part which should be replaced if deformed. The latter needs replacing with the exact shape as these do vary. Taking the part to a bike shop is the best way to ensure this.
If the hanger is part of the frame then best take it to the shop and them do the job as it can be tricky without the tool.

ratsbeyfus

Be careful though, as sometimes the mech bends instead of/as well as the hanger. Happened to me, and took ages to get correct 'diagnosis' of problem. Best to:

1. Use the shimano docs to re-index gears correctly first (though they shouldn't have gone out of kilter when your bike fell over);

2. If re-indexing doesn't work, buy a replacement rear-mech hanger.

3. If that don't work - take it into LBS for assessment/repair.

4. If feeling lazy/rich just do step 3 straight away instead.

Good luck.