Originally Posted by BlueDevil63

Things I always check:

derailleur alignment, in particular dropout hanger alignment. Cage should be in line with freewheel cogs in both up down and front back. Either derailleur cage or hanger can be bent. I find that about 50% of the bikes I work on have bent hangers. I have found very few bent cages. This can cause chain to rub on derailleur cage.

cage spring tension. Many of the older RDs have weakened springs. The spring in cage pivot has two holes in both the pivot cover and the cage. You can move the spring to the other hole(s) to get more tension on the chain in the lower gears.


It would be useful to see a picture of the bike in small-small gears to see how much chain slack the RD is taking up. If chain length is right and spring tension is good RD should be close or to max chain take up in those gears. Can we assume you have checked chainline and that it is in a reasonable range? Your pulleys look fine.