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Old 06-15-08, 10:19 PM   #1
goldfishin
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anything wrong with bending back aluminum derailleur hanger?

it was bent a bit after a mild fall today. i bent it back. should i fear catastrophic failure? seems a waste to replace it.
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Old 06-15-08, 10:38 PM   #2
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Aluminium does not like to bend. It can't handle being bent back and forth, unlike steel. Odds are your bracket is severly weakened. Shop for a new one.
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Old 06-15-08, 11:05 PM   #3
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You should order a new one but unless the bend was severe it won't fall off from regular use unless you bend it in another fall.

There's a hint you can do that will reduce the effect of the bending back. Take the hanger off (most aluminium hangers are screwed on). What you're going to do is heat it with a propane torch to relieve the stresses of the initial bend.

To act as a marker for the temperature carbon the hanger with a candle flame or the flame from a butane lighter. Hold the hanger in the yellow flame body so it deposits some carbon black on the alloy's surface.

Now hang the haner on some steel wire or similar and heat it with a propane torch set to a medium strength flame. Play the flame back and forth over the whole hanger and heat it evenly over about a minute until the carbon black heats up and burns away. You'll find that the blackening doesn't just dissapear from the flame. It'll slowly fade as the hanger metal heats up. When the black is all gone including the last shades of it then turn off the torch and let the hanger cool naturally.

Now you can quite safely bend it back without it cracking provided, as I said before, that it's not badly bent.

I've straightened a couple of bent motorcycle clutch levers this way and one that's on a bike I still have is still just fine. I'm still enough of a skeptic to not do this to a brake lever but the clutch levers still see a lot of use and they have had zero issues.
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Old 06-16-08, 11:02 AM   #4
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Are you sure it's AL? I thought most manufacturers bolted a steel one on. I'd be a little leary if it's actually AL.
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Old 06-16-08, 11:10 AM   #5
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Originally Posted by goldfishin View Post
it was bent a bit after a mild fall today. i bent it back. should i fear catastrophic failure? seems a waste to replace it.
If it was my bike I'd order a new hanger anyway. In fact, I'd get two 'cause it's kind of a disposable part and you'll never be able to get the exact one that you need the Saturday afternoon before a big ride. Then I'd bend the existing one back to use while I was waiting for the new parts to come.
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Old 06-16-08, 11:25 AM   #6
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They're not that expensive, and it's worth the peace of mind.
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Old 06-17-08, 09:30 PM   #7
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I suppose you could die if it broke off and you got thrown into traffic, but I doubt that would happen if you chain is the right length. But if it took a significant amount of force to bend it back into shape, it's probably OK. But you should still replace it whenever you can.
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Old 06-17-08, 09:52 PM   #8
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They're not that expensive, and it's worth the peace of mind.
+1.

This site sells nothing but hangars: http://www.derailleurhanger.com/ I've never shopped with them so I cannot comment on them.

BTW - I keep an extra hangar in my Camelbak, in case I smack a rock and clear off the hangar. It happened to a buddy, but not me, yet.
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Old 06-17-08, 11:00 PM   #9
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Originally Posted by BCRider View Post
You should order a new one but unless the bend was severe it won't fall off from regular use unless you bend it in another fall.

There's a hint you can do that will reduce the effect of the bending back. Take the hanger off (most aluminium hangers are screwed on). What you're going to do is heat it with a propane torch to relieve the stresses of the initial bend.

To act as a marker for the temperature carbon the hanger with a candle flame or the flame from a butane lighter. Hold the hanger in the yellow flame body so it deposits some carbon black on the alloy's surface.

Now hang the haner on some steel wire or similar and heat it with a propane torch set to a medium strength flame. Play the flame back and forth over the whole hanger and heat it evenly over about a minute until the carbon black heats up and burns away. You'll find that the blackening doesn't just dissapear from the flame. It'll slowly fade as the hanger metal heats up. When the black is all gone including the last shades of it then turn off the torch and let the hanger cool naturally.

Now you can quite safely bend it back without it cracking provided, as I said before, that it's not badly bent.

I've straightened a couple of bent motorcycle clutch levers this way and one that's on a bike I still have is still just fine. I'm still enough of a skeptic to not do this to a brake lever but the clutch levers still see a lot of use and they have had zero issues.
And then you realize you would've waste more money doing this than just buying the replacement hanger outright. And you are not guaranteed a perfect result doing the above procedure after all that effort.
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Old 06-17-08, 11:04 PM   #10
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The derailleur hanger is slightly bent on my Vitus. It's one of the bonded aluminium ones. Will heating it up weaken the bonding agent?
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Old 06-18-08, 05:57 AM   #11
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A good LBS will have a tool that is used to straighten the hanger. Nominal charge and the shop will be able to tell you if is repairable or not.
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Old 06-18-08, 06:47 AM   #12
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Originally Posted by MudPie View Post
+1.

This site sells nothing but hangars: http://www.derailleurhanger.com/ I've never shopped with them so I cannot comment on them.

BTW - I keep an extra hangar in my Camelbak, in case I smack a rock and clear off the hangar. It happened to a buddy, but not me, yet.

I'd like to buy a hangar, but I don't have a plane to put in it
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Old 06-18-08, 07:56 AM   #13
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The derailleur hanger is slightly bent on my Vitus. It's one of the bonded aluminium ones. Will heating it up weaken the bonding agent?
Yes but heating may not be required. It all kinda depends on how bent it is.

1°? :/ 5°? 30°? 180°?
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Old 06-18-08, 08:22 AM   #14
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it was bent a bit after a mild fall today. i bent it back. should i fear catastrophic failure? seems a waste to replace it.
While I would use a derailleur hanger alignment tool to straighten it, there's no reason to replace it unless it is seriously compromised. It's designed to break before the frame or derailleur does.

+1 to the wise advice on purchasing a backup.
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Old 06-18-08, 08:25 AM   #15
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Originally Posted by MudPie View Post
+1.

This site sells nothing but hangars: http://www.derailleurhanger.com/ I've never shopped with them so I cannot comment on them.

BTW - I keep an extra hangar in my Camelbak, in case I smack a rock and clear off the hangar. It happened to a buddy, but not me, yet.
Ah ha, that's what my problem was, i kept trying to go to derailuerhangers.com...

Just ordered two for my bikes to keep as spares in my saddle pouch. I also ordered a hanger alignment gauge afew days ago... I've bent enough that i figure i might as well pick one up so i don't have to go to the LBS for that.
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Old 06-18-08, 10:58 PM   #16
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Of course they're not steel. If they were, the frame would break before the disposable hanger.

I've bent them back a couple of times before, but because they're aluminum, they get softer every time. Get a spare and keep bending it back until it fails, then replace it and order another spare.
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