One must remember the era that these derailleurs were introduced and the
ratios used at the time. The Gran Sport worked perfectly well, and
better than almost any other racing derailleur of the period, when used
with 52/48 and 14-24 (5 speed) which was almost universally used at the
time.
The Sport derailleur was designed for use on city bikes with a three
speed freewheel of 16-19-22 or a four speed 15-23. It worked perfectly
well with these ratios and it is still possible to see them in everyday
use in Italy fifty years after they were made.
Mike Barry.
In sunny Toronto.