Originally Posted by
pierce
wow, 15 is an unusually large small rear cog. 13 was more typical in the 70s.
assuming that 42T small front is paired with the classic 52T big, then 52:18 or 52:19 is nearly the same gear as 42:15....
I toured for 10 years (60s-70s) with a 47-51/13-29 10 speed (5x2) drive train. I set it up this way, trading away a rarely used (though sometimes missed) high end, for better mid-range gears.