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Rear Derailleur bent??(10 posts)

Rear Derailleur bent??gray8110
Sep 2, 2002 2:29 PM
I am still trying to figure out the problem mentioned in my previous post regarding a audible soft rattle than can be felt when I'm in the front derailleur.. It feels and sounds like the chain is rubbing against something on the rear derailleur but I don't see anything when I have it on the stand.. I've experimented with everything from cassettes and chains and the problem keeps occuring. I've even completely removed the derailleur and retuned the rear shifting, but the problem continues. I think I found the problem, but I'm so dumb after staring at bikes for two days straight that I can't tell or not. I think the rear derailleur us bent. Comparing it with my rain bike it look like the lower pulley is bent towards the rear wheel. The hanger is straight, but the derailleur appears to go in a different direction. Take a look at this photo though.. does it look bent to you??

Sorry.. Here's the picgray8110
Sep 2, 2002 2:38 PM
Sorry.. Here's the picgtx
Sep 2, 2002 3:31 PM
it's possible. Did you check the hanger?
Sorry.. Here's the picgray8110
Sep 2, 2002 3:37 PM
The hanger is straight..
How do you know?grzy
Sep 3, 2002 10:11 AM
Did you measure with a DAG-1? You'd be amazed at how easily the hanger can be bent. The $50 is well worth the investment especially if you ride MTBs where the hanger always gets wacked. On some bikes the hanger seems like it's made of butter. That being said if you wang the hanger hard enough then it's fairly easy to bend the rear der. also. I have a small collection of bent rear der.'s that I keep for parts.
Sep 2, 2002 3:36 PM
If you're sure the hanger is straight (this often should be checked with a tool made for the purpose that visually amplifies any misalignment), then the derailleur is bent. However either one of these situations suggests that you banged something firmly. IME, bent hangers are much more common, more likely to happen, and easier to fix. I'd try to find a shop that can check the hanger with the proper tool before I decided it was the derailleur. In any case, the two jockey pullies should be absolutely vertical in the plane of the cogs. Yours are not.
I'd agree with Kerryclintb
Sep 2, 2002 4:14 PM
I just purchased the tool Kerry speaks of. A Park DAG-1. Used it to check out the hanger on my primary bike, which is only 6mo old, and sure enough it needed some tweaking. At $50 for the tool, I couldn't resist since it'd probably be around $30 to have a shop do it. The hanger may look straight, but you really need the tool to make absolutely sure.

One thing you may want to check for is wear in the derailleur. Remove the chain, grab the jockey cage and hold it vertical, move it toward and away from the wheel. If there's any play that feels more like clunking or rocking, your derailleur may be worn out at the second pivot. I doubt this would be it since your bike looks to be fairly new, but you never know.
I'd agree with Kerrygray8110
Sep 2, 2002 4:30 PM
The bike is fairly but new the derailleur was a part that I pulled from the old bike when building this bike so it wouldn't surprise me if it's worn out.. As I said in the earlier post everything was fine before I took the chain and wheel off to change the cassette/chain.. I must have bumped something while taking the wheel off. I appreciate your thoughts guys.. I'll drop it off at my LBS during lunch tommorow to see what they can tell. I did bend the hanger on the other bike once. The shop straightened it, but that hanger was replaceable.. The hanger on the 5900 is not replaceable.. so I hope that if the hanger is bent it is minor. Sitting the bikes next to each other, the hangers seem to be coming down at the same angle. The RD is the only Ultegra part on the bike now, so I won't complain TOO much if I have to spend 70 bucks for a new DA derailleur.
I'd agree with KerryJohnG
Sep 2, 2002 8:18 PM
You can use a machinests rule to check the Derailleur hanger.

My money's with Kerry too.Spoke Wrench
Sep 3, 2002 7:24 AM
It looks to me like the derailleur hanger is bent in the horizontal plane. It looks to me like the front edge might be a bit closer to the bike's center line than the rear.

As a general rule when working on bikes, I like to eliminate all of the things that I can do without buying any major parts (cables and housings don't count) before I start throwing money at a problem.