CITY MODEL 1 • VERSION 1
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 Ebike 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:
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Hard, harsh riding style
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“Hits”, crashes, jumps, other “shots” to the Ebike
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High mileage
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Higher body weight
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Stronger, more fit, more aggressive rider
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Corrosive environment (wet, salt air, winter road salt, accumulated sweat)
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Presence of abrasive mud, dirt, sand, soil in riding environment
Factors that lengthen product life:
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Smooth, fluid riding style
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No “hits”, crashes, jumps, other “shots” to the Ebike
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Low mileage
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Lower body weight
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Less aggressive rider
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Non-corrosive environment (dry, salt-free air)
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Clean riding environment
WARNING: Do not ride an Ebike 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 Ebike.”
This really means “composite Ebike.”
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.