Originally Posted by
JohnDThompson
Campagnolo changed their arm design in the early 1970s to allow smaller chainrings on their road crank (144mm BCD allows a 41T ring; 151mm BCD only allows 44T). Since both the road (Strata) and track (Pista) arms are based on the same forging, the track BCD changed as well at this time.
A small sidenote: Although Campy as well as TA, Ofmega etc. did indeed make 41T 3/32" road chainrings for the Strada cranks, they did not work with most chains due to insufficient clearance with the ends of the spider arms. I had to grind ~1-2mm off mine to keep the inside of the chain link from hanging on the spider, which is uncomfortably close to the chainring bolt hole.