Focus Bikes bicycle - Page 30

58 Focus Bicycles - Bicycle Owner’s Manual
Appendix B - Bicycle Lifespan 59
•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 fre-
quent attention to this area or
replace the part.
•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 : Investi-
gate and nd the source of
any noise. It may not a be a
crack, but whatever is caus-
ing the noise should be xed
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 t the “shorten product life” prole, the more frequent
your need to inspect. The more you t the “lengthen product life” prole, 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 bers are strong and light, but when crashed or
overloaded, carbon bers 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 ber bike.”
This really means “composite bike.”
Carbon ber composites are typically a strong, light ber in a matrix of plastic,
molded to form a shape. Carbon composites are light relative to metals. Steel
weighs 7.8 grams/cm
3
(grams per cubic centimeter), titanium 4.5 grams/cm
3
,
aluminum 2.75 grams/cm
3
. Contrast these numbers with carbon ber composite
at 1.45 grams/cm
3
.
The composites with the best strength-to-weight ratios are made of carbon ber
in a matrix of epoxy plastic. The epoxy matrix bonds the carbon bers together,
transfers load to other bers, and provides a smooth outer surface. The carbon
bers 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 bers can be placed in specic orientations to optimize the
structure for particular loads. The choice of where to place the carbon bers
gives engineers a powerful tool to create strong, light bicycles. Engineers may
also orient bers to suit other goals such as comfort and vibration damping.
Carbon ber composites are very corrosion resistant, much more so than
most metals.
Think about carbon ber or berglass boats.
Carbon ber materials have a very high strength-to-weight ratio.
What Are The Limits Of Composites?
Well designed “composite” or carbon ber bicycles and components have long
fatigue lives, usually better than their metal equivalents.
While fatigue life is an advantage of carbon ber, you must still regularly inspect
your carbon ber frame, fork, or components.
Carbon ber composites are not ductile. Once a carbon structure is overloaded,
it will not bend; it will break. At and near the break, there will be rough, sharp
edges and maybe delamination of carbon ber or carbon ber fabric layers.
There will be no bending, buckling, or stretching.