Quintana Roo bicycle Owner's Manual - page 22
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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.
It is now common for the main frame to be made of metal and the fork of
carbon fiber. See Section B, Understanding composites below. The relative
ductility of metals and the lack of ductility of carbon fiber means that in a
crash scenario you can expect some bending or bucking in the metal but
none in the carbon. Below some load the carbon fork may be intact even
though the frame is damaged. Above some load the carbon fork will be
completely broken.
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
Appendix B
The lifespan of your bike and its components
1. Nothing Lasts Forever, Including Your Bike.
When the useful life of your bike or its components is over, continued use
is hazardous.
Every bicycle and its component parts have a finite, limited useful
life. The length of that life will vary with the construction and materials
used in the frame and components; the maintenance and care the
frame and components receive over their life; and the type and amount
of use to which the frame and components are subjected. Use in
competitive events, trick riding, ramp riding, jumping, aggressive riding,
riding on severe terrain, riding in severe climates, riding with heavy
loads, commercial activities and other types of non-standard use can
dramatically shorten the life of the frame and components. Any one or a
combination of these conditions may result in an unpredictable failure.
All aspects of use being identical, lightweight bicycles and their
components will usually have a shorter life than heavier bicycles and their
components. In selecting a lightweight bicycle or components you are
making a tradeoff, favoring the higher performance that comes with lighter
weight over longevity. So, If you choose lightweight, high performance
equipment, be sure to have it inspected frequently.
You should have your bicycle and its components checked periodically
by your dealer for indicators of stress and/or potential failure, including
cracks, deformation, corrosion, paint peeling, dents, and any other
indicators of potential problems, inappropriate use or abuse. These are
important safety checks and very important to help prevent accidents,
bodily injury to the rider and shortened product life.
2. Perspective
Today’s high-performance bicycles require frequent and careful inspection
and service. In this Appendix we try to explain some underlying material
science basics and how they relate to your bicycle. We discuss some of the
trade-offs made in designing your bicycle and what you can expect from your
bicycle; and we provide important, basic guidelines on how to maintain and
inspect it. We cannot teach you everything you need to know to properly
inspect and service your bicycle; and that is why we repeatedly urge you to
take your bicycle to your dealer for professional care and attention.
WARNING: Frequent inspection of your bike is important to your
safety. Follow the Mechanical Safety Check in Section 1.C of this
Manual before every ride.
Periodic, more detailed inspection of your bicycle is important.
How often this more detailed inspection is needed depends
upon you.
You, the rider/owner, have control and knowledge of how often
you use your bike, how hard you use it and where you
use it. Because your dealer cannot track your use, you must
take responsibility for periodically bringing your bike to your
dealer for inspection and service. Your dealer will help you
decide what frequency of inspection and service is appropriate
for how and where you use your bike.
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.