Page 299 of 404

Inflation -- Tire Pressure
The Certification/Tire label. which is on the rear edge of
the driver's door, or on the incomplete vehicle document
in the cab, shows the correct inflation pressures for your
tires when they're cold. "Cold" means your vehicle has
been sitting for at least three hours or driven no more
than
I mile (I .6 km).
You can operate some vehicles at reduced inflation
pressures
only when you'll be carrying reduced loads.
On those vehicles, the minimum cold inflation pressures
for a typical reduced load are printed on the Improved
Ride Tire Pressure label located
on the driver's door.
Weigh the vehicle to find the load on each tire and see
the label for the
minimum cold inflation pressures for
that load.
1 NOTICE:
~.
1
Don't let anyone tell you that underinflation or
overinflation is
all right. It's not. If your tires
don't have enough air (underinflation), you can
get the following:
NOTICE: (Continued)
NOTICE: (Continued)
Too much flexing
Too much heat
Tire overloading
Bad wear
Bad handling
Bad fuel economy.
if your tires have too much air (overinflation),
you can get the following:
Unusual wear
Bad handling
Rough ride
Needless damage from road hazards.
When
to Check
Check your tires once
a month or more. Also, check the
tire pressure of the spare tire,
6-49
ProCarManuals.com
Page 303 of 404

Dual Tire Operation
When the vehicle is new, or whenever a wheel, wheel
bolt or wheel nut is replaced, check the wheel nut torque
after
100, 1,000 and 6,000 miles ( 160, I 600 and IO 000
km) of driving. For proper torque, see "Wheel Nut
Torque" in the Index.
The outer tire on a dual wheel setup generally wears
faster than the inner tire. Your tires will wear more
evenly and last longer
if you rotate the tires periodically.
If you're going to be doing a lot of driving on
high-crown roads,
you can reduce tire wear by adding
5 psi (35 kPa) to the tire pressure in the outer tires. Be
sure to return to the recommended pressures when no
longer driving under those conditions. See "Changing
a
Flat Tire" in the Index for more information.
A CAUTION:
I
If you operate your vehicle with a tire that is
badly underinflated, the tire can overheat. An
overheated tire can lose air suddenly or catch fire.
You or others could be injured. Be sure
all tires
(including the spare, if any) are properly inflated.
Buying New Tires
To find out what kind and size of tires you need, look at
the Certificntion/Tire label.
Tlze tires installed
on your vehicle when it was new had
a Tire Performance Criteria Specification (TPC Spec)
number
on each tire's sidewall. When you get new tires,
get ones
with that same TPC Spec number. That way
your vehicle
will continue to have tires that are designed
to give proper endurance, handling, speed rating,
traction, ride and other things during normal service
on
your vehicle. If your tires have an all-season tread
design,
the TPC number will be followed by an "MS"
(for mud and snow).
If you ever replace your tires with those not having a
TPC
Spec number, make sure they are the same size,
load range, speed rating and construction type
(bias,
bias-belted or radial) as your original tires.
6-53
ProCarManuals.com
Page 304 of 404

-
A CAUTION:
Mixing tires could cause you to lose control while
driving.
If you mix tires of different sizes or types
(radial and bias-belted tires), the vehicle may not
handle properly, and you could have a crash.
Using tires of different sizes may also cause
damage to your vehicle.
Be sure to use the same
size and type tires on all wheels.
Uniform Tire Quality Grading
The following information relates to the system
developed by the United States National Highway
Traffic Safety Administration, which grades tires
by
treadwear, traction and temperature performance.
(This applies only to vehicles sold in the United States.)
The grades are molded on the sidewalls of most
passenger car tires. The Uniform Tire Quality Grading
system does
not apply to deep tread, winter-type snow
tires, space-saver or temporary
use spare tires, tires with
nominal rim diameters
of IO to 12 inches (25 to 30 cm),
or to some limited-production tires. While
the tires available on General Motors passenger
cars and light trucks may vary with respect to these
grades,
they must also conform to Federal safety
requirements and additional General Motors Tire
Performance Criteria (TPC) standards.
Treadwear
The treadwear grade is a comparative rating based on
the wear rate of the tire when tested under controlled
conditions on
a specified government test course. For
example. a tire graded 150 would wear one and a half
(1 1/2) times as well on the government course as a tire
upon the actual conditions of their use, however, and
may depart significantly from
the norm due to variations
in driving habits, service practices and differences in
road characteristics and climate.
E at-aded 100. The relative performance of tires depends
Traction -- A, B, C
The traction grades, from highest to lowest, are A, B, and
C, and they represent
the tire’s ability to stop on wet
pavement as measured under controlled conditions on
specified government test surfaces
of asphalt and concrete.
A tire marked C may have poor traction performance.
Warning: The traction grade assigned
to this, tire is based
on braking (straightahead) traction tests and does not
include cornering (turning) traction.
6-54
ProCarManuals.com
Page 384 of 404

Roadside Assistance
GMC Truck’s Roadside Assistance provides stranded
owners with over-the-phone roadside repairs, location
of the nearest
GMC Truck dealer or the following
special services:
Flat Tire Chulzge: Installation of spare tire will be
covered at no charge (customer is responsible for repair
or replacement
of tire).
Fuel Deliwry: Delivery of enough fuel for the customer
to get to the nearest service station (up to $4.00) will
be covered.
Junzp Stnrt: No-start situations which require a battery
jump start will be covered at
no charge.
Lock Out: Replacement keys or locksmith service will
be covered at no charge if you are unable to gain entry
into your vehicle. Delivery
of the replacement key will
be covered at no charge within 10 miles (16 km).
Elnergemy Towing Service: Towing to the nearest
GMC Truck dealer for warranty related disablements
will
be covered.
nip Rouring: Availability of customized trip routings
through
GMC Truck Roadside Assistance. This deluxe
computerized trip routing service
will provide highlighted
map routing, scenic or fastest route,
a listing of GMC
Truck dealers along the way, and a variety of other travel
related services.
fiip hzterruptiorz: GMC Truck Roadside Assistance will
provide reimbursement for reasonable trip interruption
expenses such as meals and lodging (up to
$500) directly
associated with
a warranty-related disablement which
requires overnight accommodations.
ProCarManuals.com