204-04-3 Wheels and Tires 204-04-3
DIAGNOSIS AND TESTING
Wheels and Tires
lnspection and Verification
Visual Inspection Chart
I Mechanical I
I Tire pressure(s) * I
I Wheel nuts I
I Wheel studs I
* Vehicles equipped with a tire pressure monitoring system must be inspected for correct operation
using the diagnostic tool.
To maximize tire performance, inspect the tires for
signs of incorrect inflation and uneven wear which
may indicate a need for balancing, rotation or
suspension alignment. Tires should also be
checked frequently for cuts, stone bruises,
abrasions, blisters and for objects that may have
become embedded in the tread. More frequent
inspections are recommended when rapid or ( extreme temperature changes occur or when road
surfaces are rough or occasionally littered with
foreign material.
As a further visible check of tire condition, tread
wear indicators are molded into the bottom of the
tread grooves. When these indicator bands become
visible, new tires must be installed.
Tire Wear Diagnosis
Uneven wear is usually caused by either excessive
camber or excessive toe on tires.
Sometimes incorrect toe settings or worn struts will
cause severe 'cupping' or 'scalloped' tire wear on
non-driven wheels.
Severely incorrect toe settings will also cause other unusual wear patterns.
Tire Vibration Diagnosis
A tire vibration diagnostic procedure always begins
with a road test. The road test and customer
interview (if available) will provide much of the
information needed to find the source of a vibration. During
the road test, drive the vehicle on a road
that is smooth and free of undulations. If vibration
is apparent, note and record the following:
- the speed at which the vibration occurs.
- what type of vibration occurs in each speed
range.
- mechanical or audible
- how the vibration is affected by changes in the
following:
- engine torque
- vehicle speed
- engine speed
- type of vibration - sensitivity:
- torque sensitive
- vehicle speed sensitive
- engine speed sensitive
The following explanations help isolate the source
of the vibration.
Torque Sensitive
This means that the condition can be improved or
made worse by accelerating, decelerating,
coasting, maintaining a steady vehicle speed or
applying engine torque.
Vehicle Speed Sensitive
This means that the vibration always occurs at the
same vehicle speed and is not affected by engine
torque, engine speed or the transmission gear
selected.
2006.0 Fiesta 1212006
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