Originally Posted by
jolly_codger
...I got to wondering why horizontal dropouts continued to be used so long... Was it for frame builders to have room for error for slight mis-alignment?
John
Yes, frames built curing the classic era with limited and somewhat primitive tooling required horizontal dropouts with screw adjusters (or some kind of adjustment) to get the rear wheel to center. Any error in chain stay length gets magnified at the tire end of the wheel at almost a 3 to 1 ratio. Even today's modern and expensive fixtures don't guarantee a center wheel result.