heat during operation. The center of the tread flexes
upward and does NOT touch the surface of the road.
Underinflation will cause rapid tread wear, loss of fuel
economy, and possibly ply separation (plies tear away
from each other).
Uneven tire inflation pressure can cause steering
wheel pull. For example, when a vehicle that has the
left front tire underinflated and the right front tire
properly inflated, the vehicle has a tendency to pull to
the left. The low air pressure in the left tire has more
rolling resistance. This action tends to pull the steering
wheel away from the normally inflated tire.
Tire Vibration Problems
When one of the front tires is vibrating, it can be
felt in the steering wheel. When one of the rear tires is
vibrating, the vibration can be felt in the center and rear
of the vehicle. Tire vibration can be attributed to
several problems, such as out-of-balance condition,
ply separation, tire runout, a bent wheel, or tie cupping.
Tire and Wheel-Bearing Noise
Tire noise usually shows up as a whine due to
abnormal tread wear or a thumping sound caused by
ply separation. Tire replacement is required to correct
Wheel-bearing noise is produced by dry, worn
wheel bearings. The bearing will make a steady
humming type sound. This is due to the rollers or balls
being damaged from lack of lubrication and are no
longer smooth. To check for a worn wheel bearing,
raise and secure the vehicle, and rotate the tire by hand.
Feel and listen carefully for bearing roughness. Also,
wiggle the tire back and forth to check for bearing
looseness. It may be necessary to disassemble the
wheel bearing to verify the problem.
REVIEW 4 QUESTIONS
What are the two basic functions of a tire?
List the six major parts of a tire.
What is the major disadvantage of a radial tire?
What information is commonly given on the tire
What is the most commonly used wheel used on
Q6. What are the two basic wheel-bearing
For a tire to be in dynamic balance, the weight
must be evenly distributed around the axis of
Learning Objective: State the purpose and describe
each wheel alignment setting. Describe the different
types of equipment used during wheel alignment
The term alignment means to position in a straight
line. Relating to vehicles, alignment means to position
the tires so they roll freely and evenly over the road
surface. The main purpose of wheel alignment is to
make the tires roll without scuffing, slipping, or
dragging under all operating conditions. Correct wheel
alignment is essential to vehicle safety, handling,
extending tire life, and achieving maximum fuel
The different types of wheel alignments are front
end alignment, thrust angle alignment, and four-wheel
1. In a front end alignment, the front only is
checked. This is fine in some cases, but are the front tires
properly positioned in front of the rear tires?
2. With the thrust angle alignment, the wheels are
squared to each other. This action will eliminate dog
tracking that you may have seen on a vehicle that
appears to be going down the road with the rear end a
foot over from the front.
3. The best way to align a vehicle is a four-wheel
alignment. This alignment will not only do what the
thrust angle alignment does but also includes adjusting
the settings on the rearofthe vehicle as well as the front.
Not all vehicles are fully adjustable, so before any
alignment always consult the manufacture's service
manual. Regular wheel alignments will save you as
much in tire wear as they cost. It should be considered
routine, preventive maintenance.
Steering geometry is the term manufacturers use to
describe steering and wheel alignment. The six
fundamental angles or specifications that are required
for a proper wheel alignment are as follows: