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As per the photos below showing visible misalignment of the rear derailleur hanger:

visible misalignment of the rear derailleur hanger

and secondly its construction (where it is built-in with the dropout and frame):

built-in with the dropout and frame

Please could you help me and describe options to repair this bent hanger?

I suspect a hanger alignment tool is only meant for use with a 'replaceable hanger'?

Thank you so much for all and any help.

  • 2
    I've straightened such hangers, using a certain size axle (I'm thinking hollow) which fits the threads, and the matching axle nut tight against it. Figure out a point of reference for "straight" before you start, then eyeball it. – Daniel R Hicks Oct 8 '18 at 11:41
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This looks to be a steel frame which has a steel derailleur hanger. Steel is much more ductile than e.g. aluminum alloys and it can be bent/realigned (reasonably) many times before it cracks.

So don't be afraid to use an alignment tool if you have one. If you don't have one, use an adjustable spanner wrench to grab the hanger and align it. Even if it is steel, be careful and do not over-bend it.

Even if the worst happens and a crack develops or the hanger falls apart, it still can often be fixed by welding, but that would be much more involved and expensive, so try to avoid that of course.

I suspect a hanger alignment tool is only meant for use with a 'replaceable hanger'?

Not really. In fact, replaceable hangers are mostly made of aluminum alloy which is more brittle than steel and survive less realignment attempts than fixed steel ones.

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    Just a comment on your otherwise excellent answer. Steel is roughly three times stiffer (less flexible) than aluminum for the same dimensions. The material characteristic you are getting at is ductility or lack of brittleness. – Eric Shain Oct 8 '18 at 14:21
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    @EricShain thanks, edited my answer to use a better adjective. – Grigory Rechistov Oct 8 '18 at 16:44
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Bike ships often have a hangar alignment tool: take it to one and see how good they can get it. Doing it by hand isn't always as good as alignment is hard & you might bend it in a different place from where it is bent already.

worst comes to worst, you can take it to a frame builder, they'll remove the old one and braze in a new one, which you can repaint with car touch up paint after. I've been through that process a fair few times. At least with steel they'll do that: turn up with Al and they turn you away

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