I came across a great article on Ibike.org discussing the engineeering aspects of frame materials. As a former design engineer I found the information very interesting especially the references to “the aluminum time bomb”….

What is the best material for a bike frame?

There is no absolute answer. It boils done to the engineering of the fame and the personal preference of the user. By choosing different tubing (tube diameter and wall thickness) and frame geometry, a skilled frame builder can make a soft or stiff frame out of steel, aluminum or alloy. It is not so much a matter of the material, but how it is used that determines the ride characteristics of a bicycle. It is a mystery what determines every individual riders personal preference. For articles on choosing a material search for “metallurgy” and “buying bikes” in the archives of the Adventure Cycling magazine on their web site: http://www.adv-cycling.org . Many of these articles were written by John Schubert, Technical Editor, Adventure Cyclist Magazine. Here is a sample of his insight, specifically touring bike frames: