Last edited by ddac; 02-01-09 at 01:09 PM.
The dropouts are the bendiest part of the rear triangle. Vertical dropouts are lighter, stiffer, quicker to change a wheel, easier to change an inflated tyre when you have limitted tyre clearance.
The only advantage of horizontal dropouts is the ability to move the axle which is useful for fixie/singlespeed/internal hub builds and for emergency bail-out for tourists. There are no advantages for the avarage racing cyclist so they dissapeared from most road bikes.
Even most frames designed specifically for the Rohloff gear hub now have vertical dropouts. Chain tension is adjusted by making the dropouts themselves horizontally adjustable as in the Civia Hyland or fitting a eccentriic adjustable bottom bracket as is done by Thorn in England.
Horizontal dropouts are still IMO the cheapest and simplest arrangement for fixed gear, single speed and most gear hub bikes. Several other arrangemnts are available to use those configurations with vertical dropouts if desired.
Boreas has Horizontal dropouts and it takes a bit of thought on how to take the wheel out- Even more 3 minutes later when you try and put the wheel back in. But once the wheel is in place- It is in place. I have had numerous occasions when I have replaced a wheel on vertical dropouts- only to find that the brake blocks do not locate properly- or the wheel is offcentre. And I have even forgotten to fully tighten the QR on verticals and wondered why The bike was so hard to ride. That does not happen with horizontal dropouts.
How long was I in the army? Five foot seven.