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Cause of Rear Derailleur Hanger Breaking

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Cause of Rear Derailleur Hanger Breaking

Old 07-09-13, 09:23 PM
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CanadianBiker32
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Cause of Rear Derailleur Hanger Breaking

Last week while riding my road bike, My Rear Derailleur Hanger broke off. What type of conditions would cause this.

Happened at top of a hill. I was just shifting to harder gear, gently so i can descend. Then whole part with my derailleur came off for no reason. Never crashed ever on this bike, never hit anything with it
bike is 6 years old. Argon 18
Suggestions to why that would break as it did? thanks
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Old 07-09-13, 09:30 PM
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There's no point in throwing out a bunch of guesses. Metal parts whose integrity has not been compromised do not break, so either the part had an original defect or was somehow stressed since that time, whether you were aware of it or not. But your title and first paragraph refer to breaking, then you say it "came off," and finally you end asking why it would break. Did it break, with a portion still attached to the bike, or did the bolt/fastener holding it on fail or come out?
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Old 07-09-13, 09:47 PM
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The actual part that connects to the derailleur broke off. So my rear derailleur was floating free.
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Old 07-09-13, 10:10 PM
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The first possible reason that comes to my mind is "chain suck". This is when the chain jams between the crank's rings while shifting under power. The chain's wedging on both rings causes the chain to ride up the "back side" of the rings and the rear der cage is rotated out, feeding the chain out. In time (brief moments) the chain either gets wedged/stuck on the underside of the chain stay or the der cage's rotation isn't enough and the chain tension continues to build. The weak link is often the mounting bolt of the rear der. With worn rings or heavy pedaling pressures chain the likehood increases. Andy.
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Old 07-10-13, 04:59 AM
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Originally Posted by CanadianBiker32 View Post
The actual part that connects to the derailleur broke off. So my rear derailleur was floating free.
Again, that is not clear, as the hanger is the part that connects to the derailleur. Is part of the hanger still attached to the frame and part to the derailleur, is the entire piece with the derailleur floating free, or did the derailleur come off the hanger?
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Last edited by cny-bikeman; 07-10-13 at 05:15 AM.
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Old 07-10-13, 05:45 AM
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Canadianbiker32, I think, cny-bikeman, would like to determine whether your bike has a replaceable RD hanger or not. My questions are which derailleur did you shift in preparation for the descent and which cassette cog were you using during the climb?

Brad
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Old 07-10-13, 05:52 AM
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Actually that is a good point. I was assuming a replaceable hanger, as I've very seldom seen an integrated hanger break, never without the derailleur going into the spokes or being fouled by a branch or similar.
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Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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Old 07-10-13, 07:28 AM
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the two most common reasons for breaking derailleur hangers are

shifting into the spokes
trying to shift into big chinring big cog combo with too short of a chain

without a more thorough inspection of the bke
this is all the info i can offer
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Old 06-21-18, 03:24 PM
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Originally Posted by CanadianBiker32 View Post
Last week while riding my road bike, My Rear Derailleur Hanger broke off. What type of conditions would cause this.

Happened at top of a hill. I was just shifting to harder gear, gently so i can descend. Then whole part with my derailleur came off for no reason. Never crashed ever on this bike, never hit anything with it
bike is 6 years old. Argon 18
Suggestions to why that would break as it did? thanks
Interesting that this happened to me last night (June 2018). I was pedalling/accelerated hard to beat a light . No shift change. Then boom....chain, rear derailleur and broken hanger are stuck in my locked up rear wheel as I skidded through an intersection ��

Funny thin that my bike is a 2014/2015 Argon 18 Radon.

hanger snapped right in halfduring hard acceleration.
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Old 06-21-18, 04:21 PM
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Acceleration puts absolutely no stress on the hanger, and neither does any kind of normal shift. Something thrown up from the street can cause catastrophic failure, otherwise it's as others have said above. Andy is right, there's little point in guessing.
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There's no such thing as a routine repair.

Don't tell me what "should" be - either it is, it isn't, or do something about it.

If you think I'm being blunt take it as a compliment - if I thought you were too weak to handle the truth or a strong opinion I would not bother.

Please respect others by taking the time to post clearly so we can answer quickly. All lowercase and multiple typos makes for a hard read. Thanks!
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Old 06-23-18, 05:27 PM
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A photo would really be helpful to this thread.
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Old 06-24-18, 10:56 AM
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Originally Posted by cny-bikeman View Post
Actually that is a good point. I was assuming a replaceable hanger, as I've very seldom seen an integrated hanger break, never without the derailleur going into the spokes or being fouled by a branch or similar.
While integral hangers on steel dropout seldom completely break, aluminum dropouts did have a problem with this; that's what prompted the move to sacrificial hangers on non-steel frames.
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Old 06-24-18, 02:18 PM
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One of these ? https://wheelsmfg.com/derailleur-han.../argon-18.html They are aluminum and can break.
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