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rear derailleur cage and jockey wheel alignment- is there a tool besides the hanger tool?

2089 Views 7 Replies 7 Participants Last post by  teK--
So my wife bent her rear derailleur up pretty badly from a crash. It's a Sram NX 12 speed.
I have the hanger alignment tool and was able to bend it back within spec.
The cage of the derailleur was bend up pretty badly so I sort of eyeballed it and got a pretty straight. It shifts pretty well on the first few gears but goes out on the upper (larger ones).
The jockey wheels aren't totally straight and I also see the cage isn't perfect.
I took the cage apart and put it in a vice to get it about as straight as I can.
The problem is that It is really hard to get it all straight. The alignment tool works great but that is for the hanger. I need the jockey wheels and cage straight.
I can't believe no on make some tool to screw on to your derailleur to help square everything up. It's seems dumb to just throw this away if the thin metal happens to bend out a 1/8"
any tips or are we supposed to eyeball it?
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the hanger yes can be straightened

when the der itself is bent, far too many variables to have 'one special tool' [make/model/version/grade/fastener/what is bent]
that maybe you can bend it back.... but in general that is a losing battle unless you can replace the
bent parts (don't try to bend back) but it is hard to measure how much and which parts of the
der are also bent, it is cage, or body, or both, and what extent....and if they can be bent back.

most times rear der is junk when bent...but it's worth trying at least to see if it will work fine.

der hanger is easy to bend back and know, yep, 100% spot-on

der cages and bodies, much harder to measure each section and determine if perfect or not unless you have the engineering diagram and tools to do special checks

also by rebending you may introduce new slop in the pivots or bushings in the der
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Thanks localhost..
I'm going to try and rig up something during a trip to lowes. If I can screw something on to the derailleur bolt and have it long and square, while sticking something through the jockey wheel bolts that are tight.. it might make it a little more obvious what is out of wack
I've had a little luck removing the pulleys and using large crescent wrenches to straighten each half individually, I think it's too difficult to try to bend them together with the pulleys installed, but it sounds like you pretty much did that. Maybe just be glad she didn't get hurt and buy a new der?, - from recent experience I can tell you that any crash that doesn't require a hospital visit is cheap!
Also make sure the cages are supposed to be straight. I dont know about Sram but i almost tried to straighten my 12spd XT cage when I discovered they are designed with an offset.
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I'm all for messing around with the part and trying t get it back to working order as a learning activity, but with such a low-end part, take this as an excuse to step up to a GX, at least. The NX level is hot garbage, and really not worth the effort.
Crescent wrench works for me for correcting twist. Your eye is the gauge. Here I'd replace at least the cage.
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