Giant momentum Anleitung Seite 37

SOME CRACKS (particularly larger ones)
MAY MAKE CREAKING NOISE AS YOU
RIDE.
Think about such a noise as a serious warning
signal. Note that a well-maintained bicycle will
be very quiet and free of creaks and squeaks.
In most cases a fatigue crack is not a defect. It is a sign that the part has been worn out; a sign the part has reached the end of its
useful life. When your car tires wear down to the point that the tread bars are contacting the road, those tires are not defective.
Those tires are worn out and the tread bar says "time for replacement." When a metal part shows a fatigue crack, it is worn out. The
crack says "time for replacement."
Fatigue Is Not A Perfectly Predictable Science
Fatigue is not a perfectly predictable science, but here are some general factors to help you and your dealer determine how often
your bicycle should be inspected. The more you fit the "shorten product life" profile, the more frequent your need to inspect. The
more you fit the "lengthen product life" profile, the less frequent your need to inspect.
Factors that shorten product life:
• Hard, harsh riding style
• "Hits", crashes, jumps, other "shots" to the bike
• High mileage
• Higher body weight
• Stronger, more fit, more aggressive rider
• Corrosive environment (wet, salt air, winter road salt, accumulated sweat)
• Presence of abrasive mud, dirt, sand, soil in riding environment
Factors that lengthen product life:
• Smooth, fluid riding style
• No "hits", crashes, jumps, other "shots" to the bike
• Low mileage
• Lower body weight
• Less aggressive rider
• Non-corrosive environment (dry, salt-free air)
• Clean riding environment
WARNING: Do not ride a bicycle or component with any crack, bulge or dent, even a small one. Riding a cracked frame,
fork or component could lead to complete failure, with risk of serious injury or death.
B. Understanding composites
All riders must understand a fundamental reality of composites. Composite materials constructed of carbon fibers are strong and
light, but when crashed or overloaded, carbon fibers do not bend, they break.
What Are Composites?
The term "composites" refers to the fact that a part or parts are made up of different components or materials. You've heard the
term "carbon fiber bike." This really means "composite bike."
Carbon fiber composites are typically a strong, light fiber in a matrix of plastic, molded to form a shape. Carbon composites are
light relative to metals. 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.
The composites with the best strength-to-weight ratios are made of carbon fiber in a matrix of epoxy plastic. The epoxy matrix
bonds the carbon fibers together, transfers load to other fibers, and provides a smooth outer surface. The carbon fibers are the
"skeleton" that carries the load.
Why Are Composites Used?
Unlike metals, which have uniform properties in all directions (engineers call this isotropic), carbon fibers can be placed in specific
orientations to optimize the structure for particular loads. The choice of where to place the carbon fibers gives engineers a powerful
tool to create strong, light bicycles. Engineers may also orient fibers to suit other goals such as comfort and vibration damping.
Carbon fiber composites are very corrosion resistant, much more so than most metals.
Think about carbon fiber or fiberglass boats.
Carbon fiber materials have a very high strength-to-weight ratio.
What Are The Limits Of Composites?
Well designed "composite" or carbon fiber bicycles and components have long fatigue lives, usually better than their metal
equivalents.
SIMPLE RULE 5:
Investigate and find the source of any
noise. It may not be a crack, but
whatever is causing the noise should
be fixed promptly.
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