Originally Posted by
Chombi
Per my experience, these RDs that do not have sprung upper pivots should always operate with the RD body always against the dropout stop and all the movement on the vertical plane only happening on the derailleur cage/ jockey wheels. It maybe that the lower pivot spring on your Huret RD might be worn out or you might have to wind in some more preload into it if it is possible as with other RDs.
You might also need to experiment a bit with you chain legnth, as it might be just a bit too long.
+1 The multi spring Huret contimuose tension design Dr's are a little different than most of use deal with on these you can basically lock the mount bolt down and setup the DR and it should work for your gearing setup the tigher 24 spring setting is correct. If you have it working good just dont' over think and just ride ride it. Literaly a million plus people have riden a lot of miles these without major issues most 60's-70's Schwinns and about half of the British stuff. Had these stock.