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Discussion Starter · #1 ·
I got my pride and joy back after lending it to a friend for a few weeks and I think my Ultegra 6500 rear derailler is bent.
My question is if lines were drawn through the centers of the pulley axles and the mounting bolt should they be parallel through the full range of motion? Mine are definitly not. The pulley bolts angle towards the mounting bolt a little. The hanger isn't bent. I checked that with a gauge. The pulleys are running at an angle to the chain causing a lot of noise. There are no obvious signs of damage and that is what puzzles me. I've bent probably a half dozen XT deraillers on my mountain bike and they all had stress cracks of some sort.

Thanks
 

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Two planes

Your derailleur pulleys should be in a horizontal and vertical plane with the cogs on the cassette. IOW, when you sight the pulley cage, both pulleys should line up vertically with the cogs, and they should be parallel with the center line of the frame, which is parallel to the center line of any given cog. This is a better way to think about it than relative to the derailleur mounting bolt. While your derailleur can be bent, more likely it would be the derailleur hanger that is bent.
 

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Most any bike can have the hanger straightened by a competent mechanic. With 10-speed systems, I've found that the hanger needs to be almost perfect for the shifting to work well. Typically, what will happen, is that it shifts well going one direction on the cassette, but not the others. A shop can check it pretty easily and fix it in just a few seconds. Should only run you whatever the price of a derailleur adjustment is (typically $10).
 
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