I am trying to replace the rear derailleur on a vintage Mercier I got for free. I matched up the old and new derailleurs and they match, but I can’t get the new one on. Now I can’t even figure out how the old one goes back in as I neglected to take pics beforehand. All the images online show a small screw just behind, but in line, with the opening for the axle, but there’s nowhere for that screw to go. See pics for details. I haven’t lost any parts and the bike worked before.
by NorthWoodsEngineer_
2 Comments
Just screw it until the end of the long dropout; the screw is attached to a specially shaped lock ring that slides right in the dropout.
[Here](https://imgur.com/a/qhAR0PL) is my old setup. Hope it helps. I will warn you that these simplex parts are prone to breaking as they are plastic and the jockey wheels are next to impossible to find one that works. Its worth it to replace it if your going to ride it regularly.