Pontiac Fiero 1988 Service Manual page 206

TIRES AND WHEELS 3E-3
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Fig. 4 Tire Placard
METRIC WHEEL SMUTS A N D STUDS
Some models use metric wheel nuts and wheel
studs. The nut will have the word "metric" stamped on
its face and the stud will have the letter "M" stamped
into the threaded end. The word "metric" is stamped
on its head.
The thread size of the metric wheel nuts and
wheel studs are "Ml2 x 1.5". These stand for:
M = Metric
12 — Diameter in millimeters
1.5 — Millimeters per thread
If a broken stud is found, see Section 3C (Front
Suspension) or Section 3D (Rear Suspension) for
replacement procedure.
I N F L A T I O N O F T I R E S
The pressure recommended for any model is
carefully calculated to give a satisfactory ride,
handling, tread life and load carrying capacity.
Tire pressure, with tires cold, (after car has set for
three hours or more, or driven less than one mile)
should be checked monthly or before any extended trip
and set to the specifications on the tire placard located
on rear face of driver's door. Tire inflation pressure is
also given in Section OB.
Valve caps or extensions should be on the valves
to keep dust and water out.
1. For s u s t a i n e d d r i v i n g a t s p e e d s u p t o 8 5
m p h | 1 4 0 k m / h ) ,
in countries where such
speeds are allowed by law, your tires should be set
at the pressures recommended on your tire
placard.
S u s t a i n e d d r i v i n g a t s p e e d s
f a s t e r t h a n 8 5 m p h ( 1 4 0 k m / h ) , w h e r e
p e r m i t t e d by l a w , is n o t a d v i s e d
unless
your car has special high speed tires available
from many tire dealers.
2. Tire pressures may increase as much as 6 psi
when hot.
3. Higher than recommended pressure can cause:
m Hard ride
© Tire bruising or carcass damage
m Rapid tread wear at center of tire
4. Lower than recommended pressure can cause:
® Tire squeal on turns
m Hard steering
o Rapid and uneven wear on the edges of the
tread
• Tire rim bruises and rupture
• Tire cord breakage
• High tire temperatures
• Reduced handling
• High fuel consumption
5. Unequal pressure on same axle can cause:
• Uneven braking
• Steering lead
• Reduced handling
• Swerve on acceleration
T I R E R O T A T I O N
Figs. 5 a n d 6
To equalize wear, rotate tire and wheel assemblies
at intervals specified in Section OB. In addition to
scheduled rotation, the tire and wheel assemblies
should also be rotated whenever uneven tire wear is
noticed.
Due to their design, radial tires tend to wear
faster in the shoulder area particularly in front
positions. Radial tires in non-drive locations may
develop an irregular wear pattern that can increase tire
noise if not rotated. This makes regular rotation
especially necessary.
After rotation, be sure to check wheel nuts for
specified torque.
A C C E P T A B L E R O T A T I O N P A T T E R N
F O R R E A R W H E E L D R I V E C A R S
LI H
DO N O T I N C L U D E " T E M P O R A R Y U S E O N L Y "
S P A R E T I R E IN R O T A T I O N
H35928-3E-BG
Fig. 5 Tire Rotation - Rear-Wheel Drive
T I R E C H A I N U S A G E
Fig. 7
Due to limited tire-to-body clearance on certain
cars, tire chain usage recommendations have been
published in the Owner's Manual. When chains are to
be used, most current GM cars require SAE Class "S"
tire chains. These may also be designated as 1100
Series, Type PL tire chains. These chains are specially
designed to limit the "fly off effect that occurs when
the wheel rotates.
Manufacturers of tire chains have a specific chain
size for each tire size to ensure proper fit when