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I accidentally ran a bungee strap through my old rear deraileur and it tore it apart. I have fitted an identical replacement but cannot work out how to adjust it so that the tension pulley does not collide with the spokes of the rear wheel.

The original rear derailleur, damaged

The original rear derailleur, damaged

(hi-res version here )

Originally I bought the bike new from the LBS, who built it. It looks like they may have bent deliberately the metal frame that holds the guide pully but I'm a little anxious about trashing a brand new derailleur without confirmation that this is the best solution.

I ride a Surly Crosscheck and this rear derailleur is the standard spec so it seems more likely that the crunch has damaged another part or I have misfitted the rear derailleur.

What is the likely problem that is causing the guide pulley to collide with the spokes when I switch to the large sprocket?

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1  
Can we see a photo of the frame where the derailleur attaches? With and without the new derailleur. –  alex May 13 '13 at 9:43
    
Yes, this would still be useful for the next person who comes along with a similar problem. –  James Bradbury May 13 '13 at 12:34
    
Unfortunately (fortunately) I already had it straightened out at the LBC this afternoon with no problems. I'll take pictures and photoshop the effect where it was bent to demonstrate and upload those. It's worth pointing out that I was able to cycle to the LBC with the new derailleur fitted on the bent hanger as long as I avoided the lowest gears. –  JustinJDavies May 14 '13 at 0:17

1 Answer 1

up vote 5 down vote accepted

I guess the derailleur hanger or the bit of frame it connects to must be bent. These can be bent back. Of course Sheldon Brown has some advice, but I'd be afraid to do this myself and instead take it to the LBS who will have the tools.

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I just looked at some alignments and the frame is bent inwards. –  JustinJDavies May 13 '13 at 9:51
    
Yeah, any time something tangles with the derailer, especially if it's enough force to damage the derailer, there's danger than the derailer hanger will be bent. –  Daniel R Hicks May 13 '13 at 11:07
2  
The LBC has a special tool and are able to straighten the hanger no problems. Apparently this might not be so easy if you have a composite or aluminium frame but the Surly is a steel-frame and should bend back fine. –  JustinJDavies May 13 '13 at 11:12
    
Glad to hear it - steel for the win! –  James Bradbury May 13 '13 at 12:33

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