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I snapped my rear derailleur hanger yesterday on a ride and I wanted to know how might this have happedned and if so how can I prevent doing it in the future, I believe I was in the wrong gear going up a hill then I turned round to go down and changed through a few gears at once and when I started to pedal I heard a big snap and my chain had snapped and my rear mech hanger too.

As well as that how do I find the right replacement mech hanger for my bike, a Felt Z95 with a 12-30 cassette? Also How can I check my chain for damage, is it ok to rejoin it and use it again or would I end up making it too short or something like that? Thanks for an answers.

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    Did you save all the broken parts of the old hanger? It won't be fixable, but is often necessary to identify the correct replacement.
    – Criggie
    Aug 26, 2021 at 11:21
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    Yes I did, I have everything that broke
    – Charlie
    Aug 26, 2021 at 11:48
  • This outfit has a fairly comprehensive selection of replacement hangers: wheelsmfg.com Aug 26, 2021 at 12:56
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    The hanger is to bike what a fuse is to an electric circuit. Get a new one as as well as one extra for future similar accidents.
    – Carel
    Aug 26, 2021 at 15:18

3 Answers 3

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Likely the chain broke form a poor/incomplete shift under load, the broken end jammed in the derailleur, and the hanger did its job and broke off before more expensive damage was done.

I would put on a new chain. While it might be salvageable, my experience is once broken this way chains can be temperamental. You will also have a lost a link, so its likely (unless you have left over lengths from fitting the chain) the repaired chain will be too short.

The derailleur could be damaged, inspect it closely and be prepared for a new one if you have trouble once you get a new hanger installed.

You LBS will be able to order one in (If they are a Felt dealer they may have one in stock), otherwise All wheels manufacturering make a huge range of hangers.

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    Another possible reason is a too short chain. Or tree branches getting caught in the chain.
    – Michael
    Aug 26, 2021 at 11:42
  • What does a too short chain cause, as if I rejoined it with a quick Link like all the GCN videos say, would this affect it?
    – Charlie
    Aug 26, 2021 at 11:49
  • A too short chain can damage your rear derailleur or derailleur hanger when you try to shift to the big-big sprocket/chainring configuration.
    – Michael
    Aug 26, 2021 at 12:02
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    So lets say I get rid of 1 damaged link and replace it with a quick link, surely then it would be the same length?
    – Charlie
    Aug 26, 2021 at 13:51
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    @user57888: if a link breaks while on the drive train it is highly likely that the links left and right of the broken one are damaged as well. Better replace the chain and check for the correct length. There are several ways to find the required length. (Check GCN or Park!)
    – Carel
    Aug 26, 2021 at 15:26
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Derailleur hangers are easy to find replacements for. People have mentioned Wheelsmfg but there are other options.

BETD in the uk (Felt hangers) (is yours hanger 59?)

WheelsMfg in the US (Felt hangers)

PILO from Israel

There are others that I know of but don't list Felt. All of these are CNC machined from a superior type of aluminium than the felt originals and tend to be stiffer which makes shifting a bit better and the hanger more durable. You should be able to recognise the shape of yours from the limited selection for your brand of bike. Pilo provide measurements which is often very helpful. OEM items are usually lower quality cast metal but generally aren't any cheaper.

As others have pointed out, the chain is the suspect for why this happens but it could also be that you've been riding with a bent hanger for quite a while (happens surprisingly often) and your margin for error on a bad shift is therefore reduced. Your derailleur could quite easily be ruined and it's a good idea to change the chain, bearing in mind that you may need to change the cassette too if the bike has done alot of work since last time. All the associated components will therefore need checking carefully.

Hope that helps and gives a balanced set of options.

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Beware of too short a chain. They will sometimes work just fine until you shift to big-big and the chain jams so you can't turn the cranks. If this is in the middle of an intersection it can get ugly. Out on the road the only way to fix this is to remove one derailer pulley (or both) which gives you a bit of slack to move the chain to smaller cogs. Then you have the fun of getting the pulleys back in; if you have a Quicklink it may be quicker to break the chain to do this. And get the right length chain ASAP.

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  • Hi, welcome to bicycles. I'm not sure what this is in response to, since the original question was about a broken derailleur hanger. (And both the existing answers suggest replacing the chain as well.)
    – DavidW
    Nov 5, 2021 at 16:23
  • In the comments above someone mentioned a short chain as a possible cause of that mangled derailer. Frankly I doubt it as the chain jamming as I described is the big problem with short chains IME. My answer was in response to that comment and was not meant as an answer to the OP. Sorry. Nov 6, 2021 at 21:43

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