Scott Smith wrote:
>
> When did the rear spring design change in the NR rear derailleur and
> why? Also, why did the cage design change on the later Super Record
> rear derailleurs?
The parallelogram spring on the Super Record / Nuovo Record rear derailleur was originally located between the upper pivots of the body on a separate post. With the introduction of the Anniversary group derailleur the spring was moved to the lower back pivot and made concentric with it. The later Nuovo Record derailleur was change to the same configuration (I personally haven't seen a late Super Record derailleur with the new spring location however).
In its original location, the spring rubbed against the inner body creating friction. With the spring concentric with the pivot this rubbing friction was eliminated.
The pulley cage of the later Super Record derailleur was changed to improve shifting on larger cogs from what I understand.
Chuck Schmidt
South Pasadena, Southern California
http://www.velo-retro.com (reprints, T-shirts and Campagnolo Timeline)