Quintana Roo bicycle Owner's Manual - page 23
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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
compo nent 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
What to look for (continued):
• 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.
SIMPLE RULE 5 :
Investigate and find
the source of any
noise. It may not a be
a crack, but whatever
is causing the noise
should be fixed
promptly.
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
What to look for:
• ONCE A CRACKS STARTS IT CAN
GROW AND GROW FAST.
Think about the crack as forming a
pathway to failure. This means that any
crack is potentially dangerous and will
only become more dangerous.
SIMPLE RULE 1 :
If you find crack, replace
the part.
•
CORROSSION SPEEDS DAMAGE.
Cracks grow more quickly when they
are in a corrosive environment. Think
about the corrosive solution as further
weakening and extending the crack.
SIMPLE RULE 2 :
Clean your bike,
lubricate your bike,
protect your bike from
salt, remove any salt as
soon as you can.
• STAINS AND DISCOLORATION
CAN OCCUR NEAR A CRACK.
Such staining may be a warning sign
that a crack exists.
SIMPLE RULE 3 :
Inspect and investigate
any staining to see if it is
associated with a crack.
• 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.
SIMPLE RULE 4 :
Do not scratch, gouge
or score any surface.
If you do, pay frequent
attention to this area or
replace the part.
The basics of metal fatigue
Common sense tells us that nothing that is used lasts forever. The more
you use something, and the harder you use it, and the worse the conditions
you use it in, the shorter its life.
Fatigue is the term used to describe accumulated damage to a part caused
by repeated loading. To cause fatigue damage, the load the part receives
must be great enough. A crude, often-used example is bending a paper
clip back and forth (repeated loading) until it breaks. This simple definition
will help you understand that fatigue has nothing to do with time or age. A
bicycle in a garage does not fatigue. Fatigue happens only through use.
So what kind of “damage” are we talking about? On a microscopic level,
a crack forms in a highly stressed area. As the load is repeatedly applied,
the crack grows. At some point the crack becomes visible to the naked eye.
Eventually it becomes so large that the part is too weak to carry the load
that it could carry without the crack. At that point there can be a complete
and immediate failure of the part.
One can design a part that is so strong that fatigue life is nearly infinite.
This requires a lot of material and a lot of weight. Any structure that
must be light and strong will have a finite fatigue life. Aircraft, race cars,
motorcycles all have parts with finite fatigue lives. If you wanted a bicycle
with an infinite fatigue life, it would weigh far more than any bicycle sold
today. So we all make a tradeoff: the wonderful, lightweight performance
we want requires that we inspect the structure.