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Rear derailleur damage

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Rear derailleur damage

Old 01-23-18, 09:05 AM
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SwoozM8
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Rear derailleur damage

Alright so I was riding my bike some months ago and had an accident, long story short I fell down, went to the hospital and my bikes rear derailleur got damaged, I ride bikes for some years now and I know how to fix a flat, but not his. What parts will I need to fix it? ( i know I'm gonna need new rear derailleur )

my rear derailleur
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Old 01-23-18, 09:06 AM
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Oh well, i cant upload a pic of my derailleur
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Old 01-23-18, 09:16 AM
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Do you have a rear derailleur hanger? If so, is that bent? Could you just replace the hanger?

If you do need to replace the derailleur, you will need to have a chain tool to break then reconnect the chain. Maybe you should get a new chain too if you've been using it for a couple of seasons. And, as long as you're at it, how many miles does your cassette have? Probably time to replace that too - especially if you replace the chain. Of course you may as well replace the cables (how is the cable housing?) while you're at it. I wonder if your accident might have damaged your wheel. Better check that. Good time to replace your brake pads. And if your wheel is damaged, chances are the tire has a good gash in it too. You know, new bikes are on sale and if you've been considering a new bike anyway, well this is the time to do before you spend all your money fixing this one up because it's hard to tell if the frame didn't get a little out of alignment.

Yeah.... you see how effective I could be as a bike mechanics up-selling all kinds of services? But, all of the things I mentioned could be issues.
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Old 01-23-18, 10:22 AM
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As practical mentioned... first thing I'd look at is the derailleur hangar and see if it's bent. If it's replaceable, it's usually only a $5-10 part. Rear derailleurs are generally pretty tough parts... if you managed to damage the derailleur itself, you might want to have the bike checked for other damage as well. Derailleur hangars on the other hand can be pretty soft depending on the bike. I snapped three on my Giant Propel [only one due to a crash] and got to where I'd cary a spare in my saddle bag after the first two.
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Old 01-23-18, 10:50 AM
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What parts will I need to fix it? ( i know I'm gonna need new rear derailleur )
yea even if you buy a replacement derailleur hanger you still need the services of a bike shop and its hanger alignment tool,

just replacing the part alone wont necessarily have it brought back into alignment..

and once at that bike shop they can see what issues your bike may have.. realistically, pictures are no substitute..




...
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Old 01-23-18, 11:18 AM
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Well, it's completely destroyed, had a bad crash. If i get a new one Is it possible to align it my self?
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Old 01-23-18, 12:23 PM
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Originally Posted by SwoozM8 View Post
Well, it's completely destroyed, had a bad crash. If i get a new one Is it possible to align it my self?
Yes. I've managed to stumble through installing a new derailleur and I'm rather inept.
There are numerous videos out there that will help. See if Park Tool has one; if not, check out YouTube.
That being said, I had so much problems with my 2nd one (this one was just replacing the hanger) that I ended up taking it to the LBS.
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Old 01-23-18, 01:20 PM
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Alright, thanks for telling me that, the thing is we don't have a bike shop in my village and we don't have a car to transport it to one.
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Old 01-23-18, 02:47 PM
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Some points
1) You have to ensure that the hanger (whether integral or replaceable) is aligned properly. This may mean bending it if integral, or replacing it if its replacable and has been badly bent. In both cases you need some way to ensure that the RD mounting bolt is parallel to the axle. This means buying or fabricating a testing/bending tool.
2) Next, you have to ensure that the derailleur is not fatally damaged. The pantograph mechanism has be smooth and low friction. The jockey wheel carrier has to be perpendicular to the RD mounting bolt. It sounds like you know that your RD is kaput. So buy a new one (or a used one off ebay, if you trust ebay).

To answer your question, you need a new derailleur, and likely a new hanger (if yours is replaceable). And you need the tool to check and correct the RD mounting bolt alignment. A Park Tool DAG 2.2 is kind of standard. If you can find a shop, it will be cheaper to have them do it. Or, buy used off ebay and sell it after you've aligned your frame.

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Old 01-24-18, 11:11 AM
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Originally Posted by SwoozM8 View Post
Well, it's completely destroyed, had a bad crash. If i get a new one Is it possible to align it my self?

The more speeds the cassette has the harder it is to do "by eye". 6-7-8 speed you have a better chance than 9-10-11
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Old 01-25-18, 09:33 AM
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I recently went through this, I bent the hanger and destroyed the derailleur. Start my knowing the material the bike and hanger are made from. In my case i ride a steel mountain bike which has an integrated hanger. I have a 7 speed cog. I was able to bend it back slowly with a crescent making sure it was aligned as best i could. you can mount the derailleur use the guide cogs as a guide to it being in line with the rear cassette. If you have an aluminum bike(or other material) it most likely has a hanger that's separate from the bike and needs to be replaced its a cheap part. RJ the bike guy has a youtube channel very good visual reference for what you are going through. Installing a derailleur is an easy task once you align or replace the hanger. It would be nice to see how bad the damage is in my case the hanger was only slightly bent. if its terribly bent its not going to be fixed easily.
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