Load on a rear derailleur hanger?

big Pete said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed? If I do cold set it back will it bend again? I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught? I did a fast shift at the bottom of the
hill then after about 50m I noticed all the problems. This is an 80's
steal frame so I have no nice removable hangers. Also I think I have
killed the threads of the hanger (derailleur was pulled out of its
mounting hole), how is that fixed?

Thank you very much

This is not a problem. Take it into a shop which has an alignment tool
and they'll just bend it back into place. You might be able to do it
yourself with a Cresent wrench but chances are that you won't get the
alignment correct and the shifting won't work well.

And it only takes 15 minutes in a good shop unless they're
complications. If the hangar is cracked then it can be cut off and a
new one brazed on by a framebuilder. Still not a big problem.

"big Pete" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed? If I do cold set it back will it bend again? I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught? I did a fast shift at the bottom of the
hill then after about 50m I noticed all the problems. This is an 80's
steal frame so I have no nice removable hangers. Also I think I have
killed the threads of the hanger (derailleur was pulled out of its
mounting hole), how is that fixed?

Steel frame means it can be bent back. If the threads are trashed, Loose
Screws/Third Hand (and probably lots of other places) sells a "dropout
saver." Basically a half nut/half bushing sleeve that you insert into the
hanger after drilling out the bad threads.

Absolute worst case scenario, use a dremel to cut the hanger off the dropout
and use an adapter claw.

Good luck!

-HW

big Pete said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed? If I do cold set it back will it bend again? I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught? I did a fast shift at the bottom of the
hill then after about 50m I noticed all the problems. This is an 80’s
steal frame

Bend it back. There is a special tool for this, but if you can't get
that a long, long wrench can work. Take the derrailluer off before
you try to bend it. Having the tool be long makes it easier (more
levarage) and also allows you to use the tool to sort of see when the
dropout is straight. You will probably have to bend it a little too
far and have it spring back. But take care - better to bend it too
little on your first try and then a little more if that is needed.

Fixing this thing once will not be a problem.

JT

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Having personally killed at least 3 derailleurs in my lifetime by
shifting them into the spokes, and also having bent the dropout at
least once (and bent it back), i can without a doubt and with
categorical surity state :

You bent your dropout because the derailleur was
mis-adjusted.

You should bend it back (assuming its not too badly mangled)
and keep your derailleurs in better adjustment next time, or
use a pie-plate spoke-protector to protect your spokes.

- Don Gillies
San Diego, CA

big Pete said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed? If I do cold set it back will it bend again? I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught? I did a fast shift at the bottom of the
hill then after about 50m I noticed all the problems. This is an 80’s
steal frame so I have no nice removable hangers. Also I think I have
killed the threads of the hanger (derailleur was pulled out of its
mounting hole), how is that fixed?

In general, dropouts on decent-quality steel frames were forged from
mild steel to allow for this type of problem. Take your frame to a good
bike shop and they should be able to re-align it for you and chase the
threads. In the event that the threads were stripped beyond the point of
salvage, there are threaded inserts available that can restore these
threads.

--

John ([email hidden])

big Pete said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed?

If the dropout is steel, you can probably bend it back into place. If
it's aluminum, and the hanger isn't a replaceable piece, then the
frame is probably trashed, but you might as well try bending it back
anyway.

Quoted message said:

If I do cold set it back will it bend again?

If the cause of the derjam isn't prevented from recurring, then yes,
the der will jam again, and the hanger will get bent again.

Quoted message said:

I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught?

IME, it has always been the case that the der jammed into the wheel
and was pulled around, but it's also possible for a stickjam in the
der to allow the der to be pulled around as the rider pedals,
particularly if the rider is out of the saddle climbing when the
jamming object strikes.

Quoted message said:

I did a fast shift at the bottom of the
hill then after about 50m I noticed all the problems.

That sounds distressingly familiar. Was this a bike that perhaps
hasn't seen any lube on the mounting bolt area in a long time? If
that pivot is gummed up and not free-moving, it can cause some strange
motions in the der, possibly resulting in a derjam. My oldest
(current) roadie had that happen shortly after I got it; that's part
of the reason that I take lots of ordinarily ignored stuff apart and
relube it when I get a new-to-me used bike.

Quoted message said:

This is an 80’s
steal frame so I have no nice removable hangers.

Yes, but the hanger is probably nice and malleable; it will most
likely be possible to put it back almost exactly where it was.

Quoted message said:

Also I think I have
killed the threads of the hanger (derailleur was pulled out of its
mounting hole), how is that fixed?

There's a nifty threaded bushing that can often be used to overcome a
stripped der hanger tab, and in many cases you can install one of the
retrofit hanger tabs that are intended for use with frames that don't
have a hanger on the dropout. For the latter option to be useful, the
der needs to have enough reach to still be able to shift on to the
largest sprocket after having been moved about 4mm to the right by the
insertion of the tab.

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First of all thank you all for all your help and advice. It is sounding like I can fix this. That threaded bushing sounds useful.
I have two more questions.

1) Will the hanger be strong enough if bent back to original position? My Thinking is like this, if the hanger bent at 100% strength it will bend at 90% strength (assuming 10% loss for cold setting).

2) What amount of sideways force does the hanger have applied to it under shifting in correct operating circumstances?

Thank you very much

Pete

big Pete said:

First of all thank you all for all your help and advice. It is sounding
like I can fix this. That threaded bushing sounds useful.
I have two more questions.

1) Will the hanger be strong enough if bent back to original position?

Almost certainly, based on personal experience. I have yet to break
one in this circumstance.

Quoted message said:

My Thinking is like this, if the hanger bent at 100% strength it will
bend at 90% strength (assuming 10% loss for cold setting).

It may get work-hardened in the process instead.

Quoted message said:

2) What amount of sideways force does the hanger have applied to it
under shifting in correct operating circumstances?

Very little as long as the rider is pedalling; somewhat more if the
chain isn't moving, but not a great deal.

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big Pete said:

I have just bent my rear derailleur hanger. Can I cold set it back or is
the frame trashed?

I would try cold-setting it. It'll probably be OK. Look for cracks after
you straighten it out. BTW, the frame isn't trashed even if the hanger
does break off. You can use a cheapo hanger that fits around the axle
at the dropout (old, cheap bikes still have them, ask at an old bike
shop).

Quoted message said:

If I do cold set it back will it bend again?

maybe. the hanger will be weaker than it was, and there always is a risk
of bending a hanger.

Quoted message said:

I have a
chicken and egg dilemma, did the hanger bend because the derailleur got
caught in the back wheel or did the hanger bend (during shifting maybe)
then the derailleur get caught?

a). The chain got snarled somehow, which jammed up the derailleur, which
then bent the derailleur hanger since you were still applying pressure.

Quoted message said:

steal frame so I have no nice removable hangers. Also I think I have
killed the threads of the hanger (derailleur was pulled out of its
mounting hole), how is that fixed?

Helicoil should fix the threads. Or, take it to a shop.

--

David L. Johnson

__o | Let's not escape into mathematics. Let's stay with reality. --
_`\(,_ | Michael Crichton
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