Originally Posted by
stevage
>I wonder if the RD was terminally damaged beyond what was obvious.
Yes, so do I. How can I tell? I'm in the lucky situation that I have an identical bike to compare against - I can't see anything obviously broken, bent, twisted etc - but it's sort of hard to tell. Any tips on what to look for?
For the problem when you move the bike backward: Certainly one should not be moving the bike backward just to do it, but it's inevitable one will do so at some point, and it should not cause serious problems if everything is adjusted and aligned properly. If you have an identical bike why just look? Switch out the derailleur first, then the wheel to isolate the cause.
You also need to
see what happens when the problem first occurs, rather than just the sound. If the derailleur starts to pivot forward before anything else happens the problem has to be at the point where the chain meets the top derailleur pulley or between the two derailleur pulleys, the latter being very unlikely.
The short chain is not likely the issue, though it certainly should be corrected.