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When It Is Time for New Tires
Various factors, such as maintenance, temperatures,
driving speeds, vehicle loading, and road conditions,
influence when you need new tires.
One way to tell when it is
time for new tires is to
check the treadwear
indicators, which appear
when your tires have only
1/16 inch (1.6 mm) or less
of tread remaining.
Some commercial truck tires, including Goodyear
LT225/75R16 G949 RSA and Goodyear LT225/75R16
G933 RSD, may not have treadwear indicators. If the
tires do not have treadwear indicators, replace the tires
when the tread depth is down to 1/8 inch (3.2 mm) for
the front tires, or 1/16 inch (1.6 mm) for the rear tires.You need new tires if any of the following statements
are true:•You can see the indicators at three or more places
around the tire.
•You can see cord or fabric showing through the
tire’s rubber.
•The tread or sidewall is cracked, cut, or snagged
deep enough to show cord or fabric.
•The tire has a bump, bulge, or split.
•The tire has a puncture, cut, or other damage that
cannot be repaired well because of the size or
location of the damage.
The rubber in tires degrades over time, even if they are
not being used. This is also true for the spare tire, if your
vehicle has one. Multiple conditions affect how fast this
aging takes place, including temperatures, loading
conditions, and inflation pressure maintenance. With
proper care and maintenance tires will typically wear out
before they degrade due to age. If you are unsure about
the need to replace your tires as they get older, consult
the tire manufacturer for more information.
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Uniform Tire Quality Grading
Quality grades can be found where applicable
on the tire sidewall between tread shoulder
and maximum section width. For example:
Treadwear 200 Traction AA
Temperature A
The following information relates to the system
developed by the United States National
Highway Traffic Safety Administration (NHTSA),
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 (UTQG)
system does not apply to deep tread, winter-type
snow tires, space-saver, or temporary use
spare tires, tires with nominal rim diameters
of 10 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 (1.5) times as well
on the government course as a tire graded 100.
The relative performance of tires depends 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.
Traction – AA, A, B, C
The traction grades, from highest to lowest, are AA,
A, B, and C. Those grades 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.
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Page 357 of 440
Removing the Spare Tire and Tools
If you have a cargo van or a passenger van, the
equipment you will need is located in the passenger
side rear corner of the vehicle.
Remove the retaining wing bolt and lift it off of the
mounting bracket.
If you have a van with the 15-passenger seating
arrangement, the equipment you will need is secured
on the rear floor of the passenger side of the vehicle.To access the equipment, remove the retaining wing
bolt and lift it out of the mounting bracket.
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The tools you will be using include the jack (A),
jack handle (B), hoist extension (C), jack handle
extension (D), and the wheel wrench (E).
The spare tire is mounted in the rear underbody of the
vehicle.
You will use the hoist extension, the jack handle
extensions and the wheel wrench to remove the
underbody-mounted spare tire.To lower the spare tire from the vehicle:
A. Spare Tire
B. Tire/Wheel Retainer
C. Hoist Cable
D. Hoist AssemblyE. Hoist Shaft
F. Jack Handle and
Hoist Extensions
G. Wheel Wrench
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Page 359 of 440

1. Assemble the wheel wrench (G) to one or two of
the jack handle extensions and the hoist extension.
Insert the hoist extension end through the hole
in the rear bumper.
2. Be sure the hoist extension end connects to the
hoist shaft (E). The chiseled end of the extension
is used to lower the spare tire.
3. Turn the wheel wrench counterclockwise to lower
the spare tire to the ground. Continue to turn the
wheel wrench until the spare tire can be pulled out
from under the vehicle.
If the spare tire does not lower to the ground, the
secondary latch is engaged causing the tire not to
lower. SeeSecondary Latch System on page 6-97.4. When the tire has been lowered, pull the tire toward
you so you can reach the tire retainer and pull it up
through the wheel opening.
If you have a vehicle which was completed from
a cab and chassis, refer to the information
from body supplier/installer.
The spare tire is a full-size tire, like the other tires
on the vehicle.
5. Put the spare tire near the flat tire.
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Removing the Flat Tire and
Installing the Spare Tire
If your vehicle has plastic wheel nut caps, loosen
them by turning the wheel wrench counterclockwise.
The wheel nut caps are designed to remain with
the center cap. Remove the center cap.
If the wheel has a smooth center piece, place the chisel
end of the wheel wrench in the slot on the wheel and
gently pry it out.
1. Do a safety check before proceeding. SeeChanging
a Flat Tire on page 6-86for more information.
2. Loosen all the wheel nuts with the wheel wrench.
Do not remove them yet.3. Assemble the jack and tools:
Front Flat:Assemble the jack (A) together with the
jack handle (B), 1 or 2 jack handle extensions (D)
and the wheel wrench (E).
Rear Flat:Assemble the jack (A) together with the
jack handle (B), 2 jack handle extensions (D),
and the wheel wrench (E).
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{WARNING:
Getting under a vehicle when it is jacked up is
dangerous. If the vehicle slips off the jack you
could be badly injured or killed. Never get under
a vehicle when it is supported only by a jack.
{WARNING:
Raising your vehicle with the jack improperly
positioned can damage the vehicle and even make
the vehicle fall. To help avoid personal injury and
vehicle damage, be sure to fit the jack lift head into
the proper location before raising the vehicle.5. Raise the vehicle by turning the wheel wrench
clockwise. Raise the vehicle far enough off the
ground so there is enough room for the spare
tire to fit.
6. Remove all the
wheel nuts.
7. Take flat tire off of the mounting surface.
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{WARNING:
Rust or dirt on a wheel, or on the parts to which it is
fastened, can make wheel nuts become loose after
time. The wheel could come off and cause an
accident. When changing a wheel, remove any rust
or dirt from places where the wheel attaches to the
vehicle. In an emergency, use a cloth or a paper
towel to do this; but be sure to use a scraper or wire
brush later, if needed, to get all the rust or dirt off.
SeeChanging a Flat Tire on page 6-86.8. Remove any rust or dirt
from the wheel bolts,
mounting surfaces
and spare wheel.
{WARNING:
Never use oil or grease on bolts or nuts because
the nuts might come loose. The vehicle’s wheel
could fall off, causing a crash.
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