Originally Posted by
Andy_K
Was there a single thickness specification, or at least a single double-butted specification and a single non-butted specification, for Reynolds 531 before they started putting letters on it? For instance, the 1982 Trek manual says the Reynolds 531 tubes with no letters (as opposed to 531 SL also available that year) had 8/5/8 top tubes, 10/7/10 down tubes, and 8/5 seat tubes, which would seem to align with later 531 "Special Tourist" or "Club Sport". Was this consistent with pre-lettering 531?
Great question!
I always assumed there were different thicknesses of 531- for whatever porpoise the tubeset was intended for, but only marked as "butted" or "guaranteed built with..." to mean plain gauge.
My Trek 730 is just "531" but my Trek 720 is 531C. I assumed the C would be lighter as it's "competition." But the frame seems to be heavier than just the extra size and braze ons would be accounted for.