I'm just wondering if anyone can give me a little help with my 70's crossbike. It currently has Nervar 50.4BCD cranks with a single 45T chainring and an old Campag Record BB. I have a set of TA 50T outer & 40T inner chainrings that I would like to use to make it a double, but I'm a little unclear on what bottom bracket to use. Velobase has a Nervar catalogue from 1974 that says 117mm axel for a double, and Sheldon Brown has Nervar as needing an ISO rather than JIS type BB. What options do I have, if any ? Any and all help would be greatly appreciated.