This ground-breaking article, first published in a German magazine, compared the resistance of of aluminum, carbon-fiber and steel frames to fatigue failure. Damon Rinard considered the article so important that he struggled mightily to prepare a translation of it. It deserves a new translation, which appears here.

What is so important about the testing this article describes? Even the testers were surprised to find that the high-quality lightweight aluminum and carbon-fiber frames they tested were more resistant to fatigue failure than heavier, high-quality steel frames. A caveat, though, is appropriate: the results hold for a frame which is ridden hard but not damaged or abused: corrosion, nicks, dents, scratches and stresses due to incorrect installation of components could alter the results, as the article itself notes.

The company which developed the test, EFBe (Engineering for Bikes) has developed a number of additional bicycle durability tests and established a certification program. Many bicycle manufacturers have subscribed to EFBE's program. The work being done by EFBe is of prime importance and deserves wide attention.

-- John Allen

What do a blade of grass, an airplane and a bicycle have in common? Design: all three are lightweight structures, and two embody the same basic concept. The “idea” of lightweight construction is a principle of natural evolution: to achieve the best mechanical properties with a minimum of material, and so of resources. Engineers have borrowed this principle from nature, and apply it in a wide variety of projects. Desirable results follow: for example, air travel and elegant, user-friendly sporting equipment. And, in this connection, an apparently paradoxical result has revealed itself: lighter can also be more robust. Does this sound crazy? It isn’t. Light weight in connection with greater durability, however, requires a greater design effort.

Light Alone Isn’t Enough

There’s nothing special about building a bicycle frame which is merely light. Building a frame which is both light and durable is more difficult. The actual requirement, however, is to combine the lightest possible weight with sufficient stiffness and durability. Only in this case is it accurate to speak of successful lightweight construction. Also, it is necessary to clarify what is meant by “sufficient.” No frame should fail to meet certain stiffness requirements, as, for example, have been measured in tests published in TOUR Magazine -- or else the riding qualities suffer. Rating the stiffness of a frame in relation to its weight results in a parameter for the quality of the lightweight construction, which TOUR calls the STW (stiffness-to-weight) quotient. Materials differ widely in their suitability for lightweight construction. The ratio of stiffness to weight of aluminum exceeds that of all other materials which are used in bicycle frames. That statement, however, says nothing about the expected service life.

How Long Is Long Enough?