I'm vexxed. I'm working on an older bike with friction shifters and derailleurs, circa 1980s. (OK, itsa Trek.) The derailleur mounts directly into the dropout without a separate hanger like you see on cheaper bikes. When I shift the rear derailleur to the low cog--the LARGE one on the inside, it shifts UP fine. But when I want to shift it DOWN one gear to the second largest cog, it hangs up.



I tried a different derailleur. I took out a link from the chain. I adjusted the angle of the dangle. I adjusted the inside limiter so that it just doesn't go to the largest cog, and it works fine. It is just that large cog. It has 28 teeth. I have not tried a long cage derailleur. But I am not hopeful about that. I have never seen this before after working on dozens of bikes with all sorts of configurations. I'm out of ideas.



I'm hesitant to take it to a shop, because I am not confident that the mechanics have much experience with older machinery. So...??

Saul