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For your safety, understanding and communication with your dealer, we urge you to read this Appendix in its entirety. The
materials used to make your bike determine how and how frequently to inspect.
Ignoring this WARNING can lead to frame, fork or other component failure, which can result in serious injury or death.
A. Understanding metals
Steel is the traditional material for building bicycle frames. It has good characteristics, but in high performance bicycles, steel has
been largely replaced by aluminum and some titanium. The main factor driving this change is interest by cycling enthusiasts in lighter
bicycles.
Properties of Metals
Please understand that there is no simple statement that can be made that characterizes the use of different metals for bicycles.
What is true is how the metal chosen is applied is much more important than the material alone. One must look at the way the bike is
designed, tested, manufactured, supported along with the characteristics of the metal rather than seeking a simplistic answer.
Metals vary widely in their resistance to corrosion. Steel must be protected or rust will attack it. Aluminum and Titanium quickly
develop an oxide film that protects the metal from further corrosion. Both are therefore quite resistant to corrosion. Aluminum is not
perfectly corrosion resistant, and particular care must be used where it contacts other metals and galvanic corrosion can occur.
Metals are comparatively ductile. Ductile means bending, buckling and stretching before breaking. Generally speaking, of the
common bicycle frame building materials steel is the most ductile, titanium less ductile, followed by aluminum.
Metals vary in density. Density is weight per unit of material. Steel weighs 7.8 grams/cm3 (grams per cubic centimeter), titanium 4.5
grams/cm3, aluminum 2.75 grams/cm3. Contrast these numbers with carbon fiber composite at 1.45 grams/cm3.
Metals are subject to fatigue. With enough cycles of use, at high enough loads, metals will eventually develop cracks that lead to
failure. It is very important that you read The basics of metal fatigue below.
Let’s say you hit a curb, ditch, rock, car, another cyclist or other object. At any speed above a fast walk, your body will continue to
move forward, momentum carrying you over the front of the bike. You cannot and will not stay on the bike, and what happens to the
frame, fork and other components is irrelevant to what happens to your body.
What should you expect from your metal frame? It depends on many complex factors, which is why we tell you that crashworthiness
cannot be a design criteria. With that important note, we can tell you that if the impact is hard enough the fork or frame may be bent or
buckled. On a steel bike, the steel fork may be severely bent and the frame undamaged. Aluminum is less ductile than steel, but you
can expect the fork and frame to be bent or buckled. Hit harder and the top tube may be broken in tension and the down tube buckled.
Hit harder and the top tube may be broken, the down tube buckled and broken, leaving the head tube and fork separated from the main
triangle.
When a metal bike crashes, you will usually see some evidence of this ductility in bent, buckled or folded metal.
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