Giant Bicycles Owner's Manual page 40

• SIGNIFICANT SCRATCHES, GOUGES, DENTS OR
SCORING CREATE STARTING POINTS FOR CRACKS.
Think about the cut surface as a focal point for stress
(in fact engineers call such areas "stress risers," areas
where the stress is increased). Perhaps you have
seen glass cut? Recall how the glass was scored and
then broke on the scored line.
• 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 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
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
SIMPLE RULE 4 : Do not
scratch, gouge or score any
surface. If you do, pay fre-
quent attention to this area
or replace the part.
SIMPLE RULE 5 : Investigate
and find the source of any
noise. It may not a be a
crack, but whatever is caus-
ing the noise should be fixed
promptly.
Factors that lengthen product life:
•Smooth, fluid riding style
•No "hits," crashes, jumps, other
"shots" to bike
•Low mileage
•Lower body weight
•Less aggressive rider
•Non-corrosive environment (dry,
salt-free air)
•Clean riding environment
36