A couple of reasons I can think of:
1. It's a carry-over from the way road bikes were always made, before derailleur gears were common. Tradition.
2. "Vertical" dropouts require very precise frame building with no means to alignin the wheel if the frame comes out a little "off".
To me, the front facing horizontal dropouts on lightweight bikes always looked elegant when compared to the rear facing flattened pipe chainstays on the rod braked roadsters most people rode when I was a kid.
At 08:01 AM 26/08/2009 -0400, Stronglight49@aol.com wrote:
>Stupid questions:
>
>1.) Noticed something in the photos of the Della Santa frameset
>which brought to mind something which I never understood.
>Is there a reason for using horizontal dropouts on a modern
>road bike frame built for use of a rear derailleur?
>
>Call me lazy, but I really hate fidgeting with the rear wheels on
>my old bikes - especially those (now most) which have mudguards
>fitted.
>
>I have my own theories about the need for long dropouts -
>something which was never required (or wanted) on classic
>Touring bikes, even during the 1940s.
>
>So, next question:
>
>2.) What was the TRUE reason for use of long (or even shorter)
>horizontal dropouts throughout the On Topic period?
>
>Feeling rather naive, but it seems that design of most ANY derailleurs
>produced during the past 25 years or more have finally made horizontal
>dropouts... as obsolete as buttons on trouser flys.
>
>BOB HANSON, ALBUQUERQUE, NEW MEXICO, USA
John Betmanis
Woodstock, Ontario
Canada