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Old 09-05-11, 07:54 AM   #1
uber_Fred
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can bent rear derailleur pulleys be repaired or replaced?

Fuji Touring bike with Shimano Deore rear derailleur.

I was right hooked by a car a couple of months ago. I thought everything had been repaired, but recently I've noticed something. The pulley wheels on my rear derailleur aren't in line with the rest of the derailleur any more; there's a slight offset between them. So the chain doesn't stay in a flat plane anymore - instead it flares out (very slightly) as it passes through the pulleys. There doesn't seem to be a bend in the cage that holds the pulleys. Instead, it seems as if the alignment between the cage and the rest of the derailleur has been screwed up. I haven't really noticed any effect when I'm riding, which is why it took me so long to notice it. However, it does affect back-pedaling. The chain seems to get caught up in the pulleys a little bit. It's a bit of a hassle, but not an earth-shaking problem.

Can this be repaired? I thought before trying to bend it I'd check in here. Maybe I'd get a "happens all the time, it's an easy fix" piece of advice.

If it can't be easily repaired, can it be replaced (short of replacing the entire derailleur?) I've looked around at parts websites, and although I've seen pulley wheels for sale, I haven't seen the cage. So I'm guessing that it is only available as part of a complete derailleur.

A new Deore isn't going to wreck my retirement fund, but I'd like to repair it if possible because a) I hate replacing a perfectly good part as a matter of principle, and b) at some point I'd like to have the money I'm saving on gas not have to be plowed back into purchases for the bike. So far the benefits of commuting by bicycle have been primarily cardiovascular rather than financial.
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Old 09-05-11, 08:10 AM   #2
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Is the hanger straight? - get that checked first if it wasn't done in the repair


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Old 09-05-11, 09:45 PM   #3
Kimmo
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If it still looks bent once you've ensured the hanger is straight, you can remove the derailleur, wrap the cage in a rag and hold it in a vice to tweak it back by pushing on the rest of the derailleur.
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Old 09-05-11, 10:43 PM   #4
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Quote:
Originally Posted by Kimmo View Post
If it still looks bent once you've ensured the hanger is straight, you can remove the derailleur, wrap the cage in a rag and hold it in a vice to tweak it back by pushing on the rest of the derailleur.
From the description it sounds as if the outer cage were bent and the inner was following the alignment of the outer. I would take the cage apart and straighten the outer cage, possibly in a vise. I would check the inner cage too. When taking the cage apart, it may be wise to place pieces separately, marking what goes where, for ease in cage reassembly.

Cage gets deformed over time, for one reason or another, so it may be indeed useful to go over the exercise to gain experience in general. There is nothing scary about a derailleur. One can take it apart into some elementary components and then put it safely back together. Manufacturer's on-line drawing can be helpful in this.
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