From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Are "Track" Dropouts and Horizontal Dropouts the Same Thing?
Date: 30 Sep 1998 22:54:44 GMT

Steve Freides writes:

> I've heard the term 'track dropouts' bandied about, and am wondering
> what, if any, difference there might be between those and the
> more-or-less horizontal dropouts on my old Centurian Ironman that I
> ride with a fixed-gear - mine tilt slight in the direction of 10
> o'clock-4 o'clock as opposed to being truly parallel to the ground,
> but they're plenty horizontal enough for me.

That may be what you have.  They are open to the rear an allow
longitudinal positioning of the rear wheel to adjust chain length with
different sprockets (track bicycles have one rear sprocket rigidly
attached to the hub).  The range of sprockets for track is small
because one tooth up or down on the rear is usually matched by an
opposite change in the chainwheel.  Campagnolo track dropouts are 5mm
and road dropouts are 7mm minus surface grinding of about 0.1mm but
slightly more massive in the width of the jaws, allowing for
individual customization by the frame builder.

All dropouts were "track" dropouts until derailleurs came along.  You
can probably visualize that the slot must open forward or at least end
ahead of the derailleur attachment to make wheel removal convenient.
It was at that time that the term became popular because there was a
differentiation between road bike and track bikes.  My early one speed
balloon tired bicycles had rear opening dropouts with adjusting
screws.  Then someone decided to turn them around even though no
derailleurs were used on thin sheet metal dropouts.

Jobst Brandt      <jbrandt@hpl.hp.com>