I think you all may be missing two important advantages of adjustable horizontal dropouts (not that verts aren't cool-looking...).
1) Wheelbase "tuneability," allowing you to vary it because you want to, or to optimize the fit of a certain wheel/tire/brake caliper combination. The ubiquitous 1010 drops give you close to 25 mm of adjustability if you choose to go to the extremes of travel.
2) Wheel to der. pulley adjustability. Sometimes, to get a certain combination of rear derailleur and freewheel cog size to work properly, you have to tune the fore/aft location of the rear wheel axle. Chain length/wrap won't always do it.
You can adjust chain tension by adding or removing links in the chain.
Cheers,
Greg Parker
A2 MI USA
> Message: 3
> Date: Fri, 20 Sep 2002 10:34:26 -0700 (PDT)
> From: Brandon Ives <monkeylad@mac.com>
> To: "Beyer Jr., Chris (C.C.)" <cbeyer2@volvocars.com>
> Subject: Re: [CR]Vertical Dropouts
> Cc: "'Rich Rose'" <rrose@normandassociates.com>,
> classicrendezvous@bikelist.org
>
> On Friday, Sep 20, 2002, at 08:17AM, Beyer Jr., Chris (C.C.) <
> cbeyer2@volvocars.com> wrote:
> >It's horizontal dropouts, especially long ones, that bewilder me.........
>
> I'm with Chris here. I don't think the question should be why vertical, but
> why NOT vertical? I can think of only one reason for a slotted "dropouts",
> adjustable chain tension. I'm a big fan of fixed-gears, single-speeds, and
> internal hubs, but outside of these applications I see no benefits to a
> slotted "dropout." A vertical dropout is lighter and stronger on top of
> the other advantages listed by others. Most of my personal bikes will
> always have some kind of slotted "dropout" because I don't use deraileurs
> on most of my bikes.
> enjoy,
> Brandon"monkeyman"Ives
> SB, CA