Wheels That Don’t Roll
Almost every bicyclist has had the experience of getting something
in the spokes of a bicycle wheel. Sometimes it’s fun, attaching
baseball cards to a fender brace with a clothespin and making some
good noise. Some of us in our fiendish childhood explored the destructive
possibilities by using spinning wheels to grind up sticks and forcing
balloons and even unfortunate insects into our wheels.
Mountain bike riders are familiar with some of the hazards associated
with getting a stick caught in the spokes, and bicycle tourists
sometimes get straps or loosely held articles caught in the spokes
while touring. However, significant hazards exist for all riders
from objects in turning bicycle wheels. Recently, our office was
contacted by an experienced rider who had placed his bicycle light
on the front forks of his bike. The light bracket vibrated loose
and rotated backwards into the front wheel, getting caught between
a spoke and the forks, locking up the front wheel and sending him
over the handle bars at approximately 25 miles per hour. Unfortunately,
he sustained two pulverized vertebra and other injuries which, while
not life threatening, resulted in ten days in a hospital intensive
care unit, major surgery and will take months to heal. Fortunately,
he did not damage his spinal cord. Examination of the bike revealed
that the front wheel was a high performance 18 spoke wheel, with
one broken spoke from the contact with the light housing. We decided
that a jury would probably view the cause of this accident as primarily
user error and elected not to pursue a lawsuit. However, there are
a number of factors which may be of value as lessons from the accident.
First, the new high performance wheels have fewer spokes than older
style wheels. In the accident related above the front wheel had
18 spokes, compared to 28 to 36 spokes on older style wheels. Fewer
spokes means that there will be less likelihood for the spokes to
deflect or eject an intrusion. (Most bicycles have fewer spokes
in the front wheel than the rear because of the larger torsional
forces generated by the pedals to the rear wheel). While it would
be pure speculation to say that the accident would not have happened
with an older style wheel, it does seem that the newer style wheels
are more likely to have problems with intruding objects than the
older styles.
Second, riders who have yet to experience a crash caused by a spoke
obstruction probably do not fully realize how quickly these accidents
can happen. Our experience with motor vehicles is that if something
gets caught in a wheel it gets run over or wrapped around the wheel.
However, with a bicycle wheel there is much more space than there
is substance, creating many opportunities for this type of accident.
Further, the stopping power generated by having an object lodged
in the spokes is considerable; while a rider may be able to maintain
control if an object gets caught in the rear tire and causes it
to skid, few people have the ability to maintain control of a bicycle
which has its front wheel locked-at greater than walking speed the
rider is usually catapulted over the front handlebars.
Third, spokes on high performance wheels are no longer round, but
are oval or bladed, often with sharp edges (for aerodynamic reasons).
These spokes will arguably be more likely to cut some objects (like
a small twig), but they are also more likely to dig into an object
instead of pushing it aside.
Awareness of hazards creates a safety consciousness that avoids
accidents. Be aware that loose gear and debris can cause a catastrophic
accident if caught in spokes. Strap it securely or avoid it and
you may save yourself from an accident.