NortonMarg@aol.com wrote:
(snip)
> ...120 back ends started going out of favor in the
> early 70s?
No, IMHO, I think it was more mid-70s in Italy, a little later elsewhere. Virtually all top-quality Italian bikes were 120mm in the early '70s. Race team framebuilders and mechanics lead the movement around 1974/75, especially those directly involved with professional race teams. (Racers liked the extra cog despite the greater wheel dish's reliability problems since they had spare wheels in cars following the races.) And the Italian bike industry, with closer ties to Campagnolo, Everest and Regina, lead the process in general. But it was normal to see many/most high-quality factory Italian bikes still with 5 sp/120mm in 1975-77. But by 1980 nearly all were six sp/126mm.
Bill Bryant
Santa Cruz, CA