My rear derailleur is making some noise and I'm having trouble diagnosing the cause. It seems like it's coming from the rear cogs and sounds similar to chain noise. I'm re-building my bike after an accident, so it's possible that something was bent though I don't see any gross damage to the RD. I've spent some time browsing this site and others for ideas, and have checked the following:
- Checked hangar alignment
- Lubed the rear cogs
- Lubed the chain
- Checked the b-limit setting
- Indexed the gears & ensured they shift well
- Checked for chain stretch (chain only has ~250 mi on it)
Can you think of any other causes for a noisy rear derailleur? I have a video if it's helpful.
EDIT: Thanks everyone for the help and suggestions! It ended up being a combination of a bent hanger and a twisted derailleur cage. I replaced the hanger with a new one which helped to reduce the noise, but there was still some prominent noise coming from the jockey wheels, mostly on the smaller cogs, and only when in the large chainring. I changed the derailleur and the noise is now gone.