Tire Wear Diagnosis; Tread Wear Indicator; Lead; Radial Tire Waddle - Pontiac TRANS AM 1977 Service Manual

STEERING, SUSPENSION, WHEELS AND TIRES
3-1 5
HARD CORNERING INCORRECT WHEEL ALIGNMENT
UNDER INFLATIDN TIRE CONSTRUCTION NON-UNI FORMITY
CK OF ROTATION REAR WHEEL HEAVY ACCELERATION
2090
Fig.
3-1
2 Tire Wear Diagnosis
Fig.
3-13
Tread Wear Indicator
It is possible to road test a car and tell on which end of
the car the faulty tire is located. If the waddle tire is on the
rear, the rear end of the car will shake from side to side or
"waddle". From the driver's seat it feels as though someone
is pushing on the side of the car.
If the faulty tire is on the front, the waddle is more visual.
The front sheet metal'appears to be moving back and forth
and the driver feels as though he is at the pivot point in the
car.
Lead
Fig.
3-1
4 Radial Tire Waddle
2. Uneven brake adjustment.
3. Tire construction.
The way in which a tire is built can produce lead in a
car. An example of this is placement of the belt. Off center
belts on-radial tires can cause the tire to develop a side force
while rolling straight down the road. If one side of the tire
is a little larger diameter than the other, the tire will tend to
roll to one side. This will develop a side force which can
produce car lead.
The procedure in Fig. 3-1 5 should be used to make sure
that front alignment is not mistaken for tire lead.
1. Part of the lead diagnosis procedure is different from
the proper tire rotation pattern currently in the owner and
service manuals. The manuals recommend front to rear
rotation only; if a medium or high mileage tire is moved to
the other side of the car, be sure to check that ride roughness
has not developed.
2. Rear tires will not cause lead.
Lead" is the deviation of the car from a straight path
on a level road with no pressure on the steering wheel.
Lead is usually caused by:
1. Alignment.