C: What To Look For - Schwinn Hybrid Owner's Manual

Appendix A
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

1.C: 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.
• CORROSION 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.
• 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.
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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 trade off: the wonderful, lightweight
performance we want requires that we inspect the structure.
SIMPLE RULE 1:
If you find crack, replace the part.
SIMPLE RULE 2:
Clean your bike, lubricate your bike, protect your bike from salt,
remove any salt as soon as you can.
SIMPLE RULE 3:
Do not scratch, gouge or score any surface. If you do, pay
frequent attention to this area or replace the part.
SIMPLE RULE 4:
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.