Teaching Elements and Principles of Bridge Design - International ...

RESOURCES IN TECHNOLOGY
RESOURCES IN TECHNOLOGY
Wheels and Tires
John M. Ritz, DTE
Automobile wheels (rims and
hubcaps) have been catching the
eyes of car enthusiasts for years.
Designers have used their creativity
to make better products both
structurally and aesthetically.
Hubcaps were one of the early
aesthetic accessories added to
wheels to hide the nuts used to
fasten the wheels onto the vehicle.
Later, MAG wheels (originally made
of magnesium alloys to take on a
spoke effect) were developed to
increase the strength and sporty
appearance of the wheels. Both are
found in the current market; many are
replaced with fads held by automotive
enthusiasts. Some believe that the
wheels and tires are the most visible
styling statement beyond the
automobile’s color and shape. This
Resources in Technology will look at
automotive wheels and tires.
Humans learned early that simple
tools could make their work easier.
Heavy objects, e.g., rocks, trees,
boats, could be rolled by wedging
small logs under them and pushing or
pulling. No doubt this is where the
concept of the wheel developed.
History has shown that early wheels
were more easily made by fastening
planks together instead of using one
piece of heavy wood. Later, spoke
systems were developed to lighten
the weight of the wheels while
maintaining strength. Tires were
added to the wheels to increase
useful life and to make the ride less
bumpy.
Today’s vehicles that ride on land,
roadways, and railways, are all
developments or extensions of the
early two-wheeled cart. The structure
Understanding the numbers on the sides of
tires might lead to longer life tires and
improved driving safety.
or propulsion of the vehicles has
changed, but the basic concepts of
moving a load or people have stuck
to the basic vehicle concept. Today,
no vehicle is more of a necessity
than the automobile. Driving is a rite
of passage for teenagers in
developed countries.
Automotive Wheels
Early automotive wheels were no
more than bicycle wheels. These
spoked wheels had metal tires or
rims to increase their life. Because of
durability and automobile weight,
solid rims were designed. These
were forged and welded together.
Today, wheels are either made of
steel or other metallic alloys.
Traditional steel rims are forged and
welded together. Alloy wheel
construction is undertaken in three
manufacturing methods. Forged
wheels, thought to be the best
manufacturing technique, are made
by taking an alloy billet (solid piece of
material) and compressing it through
heat and pressure. This produces a
very strong, lightweight wheel. Low
pressure cast wheels are made by
pouring molten metal into a mold that
is the shape of the desired wheel.
Counter pressure casting, the third
way to produce automotive wheels,
uses a vacuum to pull the hot metal
into the mold. This method reduces
the presence of air voids in the
formed metal.
Specialty wheels are everywhere in
the automotive market. Storefront,
magazine, and newspaper ads show
how wheels can change the looks of
your automotive product. Many try to
personalize their vehicle with a new
set of wheels. Spinners are a current
fad and catch your eyes when they
continue to spin after the vehicle
comes to a stop. If you are in the
market for new wheels or tires, some
knowledge and research can prove to
be helpful in buying products that not
only look good, but also increase the
performance of your ride.
Manufacturers recommend that
replacement wheels and tires on
automotive products be matched with
those from the original design
specifications. With the increased
concentration on looks and
performance, people want to make
their vehicles look special. Some are
plus- or minus-sizing their wheels and
tires to enhance looks and
performance. It is common to see
larger diameter wheels placed on
customized cars with low profile tires.
Trucks are adding all-terrain and mud
tires for off-road performance. Experts
in the after-market wheel and tire
business recommend that the overall
size of replacement wheels should not
exceed three percent of the
manufacturer-specified wheels and
tires. If this size is exceeded,
problems can occur with proper
transmission shifting, which will
THE TECHNOLOGY TEACHER • April 2005 17