Originally Posted by
TejanoTrackie
Wrong. All types of brakes ultimately result in a maximum bending moment at the top of the fork legs where they are joined to the fork crown. The magnitude of this bending moment is determined by the actual braking force that is generated at the ground, regardless of the type of braking system. Round track fork legs have much lower bending capacity (bending section modulus) than oval road fork legs.
Round tubes are best at dealing with a wider variety of stresses and forks are stressed in every way imaginable and in combination with each other... they are subjected to bending, compression. and torsional loads stemming from their need to support, suspend, and deal with braking loads.
Oval tubes are designed to resist more specific stresses... we apply this to our frames in order to maximize certain ride qualities and meet performance goals.
The beam on our tandems is a specially drawn oval tube, and over sized as to provide vertical load support but to also provide greater resistance to torsional loads as tandems are subject to much higher loads than a single bike.
Chain stays are partly oval because they need to offer clearance for the wheel and cranks and this does make them stiffer in the vertical plane (where they are oval) but they get drawn into round tubes which meet the dropout and have extra support from the seat stay which is typically round tubing.
And then we have these fancy new bikes with long flat tubes on the frame and fork which are there primarily for advertising space.