GMC SIERRA 1993 Owners Manual

I CAUTION
Poorly maintained and improperly used tires are dangerous.
Overloading your tires can cause overheating as a result of too
much friction. You could have an air-out and a serious accident.
See “Loading Your Vehicle” in the Index:
The resulting accident could cause serious injury. Check all tires
frequently
to maintain the recommended pressure. Tire pressure
should be checked when your tires are cold.
Overinflated tires are more likely to be cut, punctured, or broken
by sudden impact, such as when you hit a pothole. Keep tires
at the recommended pressure.
Worn, old tires can cause accidents; If your tread is badly worn,
or if your tires have been damaged, replace them.
Even if it’s legal, don’t drive over 85 mph (1 35 kmlh) if you
have
16 inch tires. With 19.5 inch tires, don’t drive over 75 mph
(1 20 km/h).
Underinflated tires pose the same danger as overloaded tires.
See “Special Tire Inflation” in this section for more information on
I loading and inflation pressures at speeds above 65 mph (105 kmlh). I
Inflaiion-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 corre\
ct 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
a mile.
You can operate some vehicles at reduced inflation pressures only w\
hen 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 v\
ehicle
to find the
load on each tire and see the label
for the minimum cold inflation pressures
for that load.
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Service & Appearance Care
When to Check: Check your tires once a month or more. Also, check the
tire pressure of the spare tire.
How to Check: Use a good quality pocket-type gage to check tire pressure.
Simply looking at the tires will not tell you the pressure, e\
specially
if you
have radial tires-which may look properly inflated even if they\
’re
underinflated.
If your tires have valve caps, be sure to put them back on. They help
prevent leaks by keeping out dirt and moisture.
Special Tire Inflation
If you have 16 inch tires on your vehicle, and:
- You’ll be driving for very long at speeds of 66 mph (1 05 km/h) to 75
mph (120 kmlh) where legal, inflate tires 10 psi (70 kPa) more than
the recommended cold inflation pressure.
- You’ll be driving for very long at speeds of 76 mph (120 kmlh) to 85
mph (1 35 km/h) where legal, cold inflation pressure should be
increased by
10 psi (70 kPa) and you must also reduce axle load
capacity by
10%. Do not drive over 85 mph (135 kdh) even if
it’s legal.
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- Inflation pressures should never exceed 10 psi (70 kPa) above the
inflation specified for the maximum load of the tire.
If you have 19.5 inch radial tires on your vehicle, and:
- You’ll be driving for very long at speeds of 66 mph (105 km/h) to 70
mph (110 km/h) where legal, inflate tires- to 5 psi (35 kPa) more than
the recommended cold inflation pressures and reduce axle load
capacity by 4%.
- You’ll be driving for very long at speeds of 71 mph (1 15 km/h) to 75
mph (120 kmlh) where legal, cold inflation pressures should be
increased by
5 psi (35 kPa) and you must also reduce axle load
capacity by
12% Do not drive over 75 mph (120 kmh) even if it’s
legal.
inflation specified for the maximum load of the tire.
- Inflation pressures should never exceed 20 psi (140 kPa) above the
For special operating conditions, such as carrying a slide-in c\
amper,
increase recommended cold tire pressures
by 10 psi (70 kPa).
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Senrice & Appearance Care
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r K2691
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Service & Appearance Cam
Tire lnspecfion and Rotation
To make your tires last longer, have them inspected and rotated at the
mileages recommended in the Maintenance Schedule. See “Scheduled
Maintenance Services” in the Index.
Q
-
-
K2655
Use this rotation pattern.
If your vehicle has front tires with different load ratings or tread designs (such
as all season
vs. onloff road) than the rear tires, don’t rotate your tires \
front
to rear.
After the tires have been rotated, adjust the front and rear \
inflation pressure
as shown on the CertificationRire label. Make certain that all wheel nuts are
properly tightened. See “Wheel Nut Torque”
in the Index.
A Rust or dirt on a wheel, or on the parts to which -it is fastened, can
make the wheel nuts become loose after a time. The wh.eel could
come
off and cause an accident. When you change- a- :wheel, remove
’ any -rust or dirt from places where the wheel attaches to the vehicle:
,: In an emergency, you can use a cloth or paper towel to do this; but
3 be sure to use a scraper or wire brush later, if you need- to, to get
-T all the rust or dirf off. See “Changing a Flat Tire” in the Index.
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Dual Tire Rotation
K2659
Use one of these patterns if you have the same tire sizes and load ranges
on the front and rear.
K2660
1
Use this pattern if your front and rear tires are different sizes or load ranges.
When you install dual wheels, be sure the vent holes in the wheels are
lined up.
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Service & Appearance Cam
When It’s Time for New Tires
K1656
One way to tell when it’s time for new tires is to check the treadwear
indicators, which will appear when your tires have only
2/32 inch (1.6 mm) or
less of tread remaining.
You need a new tire
if:
You can see the indicators at three 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 can’t be repalred well
because of the size or location of the damage.
Dual Tire Operation
If your vehicle has dual rear wheels, the outer tire will usually\
wear 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.
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r 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 catcl.
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 Certificationflire
label. The 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 num\
ber. That
way, your vehicle will continue to have tires that are designed to give proper
endurance, handling, speed rating, traction, ride and other thin\
gs during
normal service on your vehicle. If your tires have an all-season tread design,
the TPC number will be followed by a
“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.
1 CAUTION
* Mixing tires could cause you to lose control while driving. If you mix
vehicle may not handle properly, and you could have a crash. Be
- ) tires of different sizes or types (radial and bias-belted tires), the
I sure to use the same size and type tires on all wheels. I
Uniform Tire Qua/ity Grading
The following information relates to the system developed by the United
States National Highway Traffic Safety Administration which grade\
s tires by
treadwear, traction and temperature performance. (This applies o\
nly to
vehicles sold in the United States.)
Treadwear
The treadwear grade is a comparative rating based on the wear rate of the
tire when tested under controlled conditions on a specified governmen\
t 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 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 var\
iations in
driving habits, service practices and differences in road characteristics and
climate.
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Service & Appearance Care
Traction-A, B, C
The traction grades, from highest to lowest are: A, B, and C. 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
(straight-ahead) traction tests and does not include cornering \
(turning) traction.
Temperature-A, B, C
The temperature grades are A (the highest), B, and C, representing the tire’s
resistance
to the generation of heat and its ability to dissipate heat when
tested under controlled conditions on a specified indoor laborat\
ory test wheel.
Sustained high temperature can cause the material of the tire to degenerate
and reduce tire life, and excessive temperature can lead to sudden tire
failure. The grade
C corresponds to a level ‘of performance which all
passenger car tires must meet under the Federal Motor Vehicle \
Safety
Standard
No. 109. Grades B and A represent higher levels of performance on
the laboratory test wheel than the minimum required by law.
Warning: The temperature grade for this tire is established for a tire that is
properly inflated and not overloaded. Excessive speed, underinfla\
tion, or
excessive loading, either separately or in combination, can caus\
e heat buildup
and possible tire failure.
These grades are molded on the sidewalls of passenger car tire\
s. While the tires available as standard or optional equipment on \
General Motors
vehicles may vary with respect to these grades, all such tires meet General
Motors performance standards and have been approved for use on \
General
Motors vehicles.
All passenger type (P Metric) tires must conform to Federal
safety requirements in addition to these grades.
Wheel AIignment and Tire Balance
The wheels on your vehicle were aligned and balanced carefully \
at the
factory to give you the longest tire
life and best overall performance.
In
most cases, you will not need to have your wheels aligned again.
However,
if you notice unusual tire wear or your vehicle pulling one way \
or
the other, the alignment may need to be reset. If you notice your vehicle
vibrating when driving on a smooth road, your wheels may need to be
rebalanced.
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