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290 Vehicle Care
passenger vehicle tire engineered to
standards set by the U.S. Tire and Rim
Association.
(2) Tire Width
:The 3-digit number
indicates the tire section width in
millimeters from sidewall to sidewall.
(3) Aspect Ratio
:A 2-digit number that
indicates the tire height-to-width
measurements. For example, if the tire
size aspect ratio is 75, as shown in
item (3) of the illustration, it would
mean that the tire's sidewall is
75 percent as high as it is wide.
(4) Construction Code
:A letter code is
used to indicate the type of ply
construction in the tire. The letter "R"
means radial ply construction; the letter
"D" means diagonal or bias ply
construction.
(5) Rim Diameter
:Diameter of the
wheel in inches.
(6) Service Description
:These
characters represent the load index and
speed rating of the tire. The load index
represents the load carrying capacity a tire is certified to carry. The speed
rating is the maximum speed a tire is
certified to carry a load.
Tire Terminology and Definitions
Air Pressure:The amount of air inside
the tire pressing outward on each
square inch of the tire. Air pressure is
expressed in kPa (kilopascal) or psi
(pounds per square inch).
Accessory Weight
:The combined
weight of optional accessories. Some
examples of optional accessories are
automatic transmission, power
windows, power seats, and air
conditioning.
Aspect Ratio
:The relationship of a
tire's height to its width.
Belt
:A rubber coated layer of cords
between the plies and the tread. Cords
may be made from steel or other
reinforcing materials.
Bead
:The tire bead contains steel
wires wrapped by steel cords that hold
the tire onto the rim. Bias Ply Tire
:A pneumatic tire in which
the plies are laid at alternate angles
less than 90 degrees to the centerline
of the tread.
Cold Tire Pressure
:The amount of air
pressure in a tire, measured in kPa
(kilopascal) or psi (pounds per square
inch) before a tire has built up heat
from driving. See Tire Pressure0292.
Curb Weight
:The weight of a motor
vehicle with standard and optional
equipment including the maximum
capacity of fuel, oil, and coolant, but
without passengers and cargo.
DOT Markings
:A code molded into the
sidewall of a tire signifying that the tire
is in compliance with the U.S.
Department of Transportation (DOT)
Motor Vehicle Safety Standards. The
DOT code includes the Tire Identification
Number (TIN), an alphanumeric
designator which can also identify the
tire manufacturer, production plant,
brand, and date of production.
GVWR
:Gross Vehicle Weight Rating.
See Vehicle Load Limits 0193.
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GAWR FRT:Gross Axle Weight Rating
for the front axle. See Vehicle Load
Limits 0193.
GAWR RR
:Gross Axle Weight Rating
for the rear axle. See Vehicle Load
Limits 0193.
Intended Outboard Sidewall
:The side
of an asymmetrical tire that must
always face outward when mounted on
a vehicle.
Kilopascal (kPa)
:The metric unit for air
pressure.
Light Truck (LT-Metric) Tire
:A tire used
on light duty trucks and some
multipurpose passenger vehicles.
Load Index
:An assigned number
ranging from 1 to 279 that corresponds
to the load carrying capacity of a tire.
Maximum Inflation Pressure
:The
maximum air pressure to which a cold
tire can be inflated. The maximum air
pressure is molded onto the sidewall.
Maximum Load Rating
:The load rating
for a tire at the maximum permissible
inflation pressure for that tire. Maximum Loaded Vehicle Weight
:The
sum of curb weight, accessory weight,
vehicle capacity weight, and production
options weight.
Normal Occupant Weight
:The number
of occupants a vehicle is designed to
seat multiplied by 68 kg (150 lb). See
Vehicle Load Limits 0193.
Occupant Distribution
:Designated
seating positions.
Outward Facing Sidewall
:The side of
an asymmetrical tire that has a
particular side that faces outward when
mounted on a vehicle. The side of the
tire that contains a whitewall, bears
white lettering, or bears manufacturer,
brand, and/or model name molding
that is higher or deeper than the same
moldings on the other sidewall of
the tire.
Passenger (P-Metric) Tire
:A tire used
on passenger cars and some light duty
trucks and multipurpose vehicles. Recommended Inflation Pressure
:
Vehicle manufacturer's recommended
tire inflation pressure as shown on the
tire placard. See
Tire Pressure0292 and
Vehicle Load Limits 0193.
Radial Ply Tire
:A pneumatic tire in
which the ply cords that extend to the
beads are laid at 90 degrees to the
centerline of the tread.
Rim
:A metal support for a tire and
upon which the tire beads are seated.
Sidewall
:The portion of a tire between
the tread and the bead.
Speed Rating
:An alphanumeric code
assigned to a tire indicating the
maximum speed at which a tire can
operate.
Traction
:The friction between the tire
and the road surface. The amount of
grip provided.
Tread
:The portion of a tire that comes
into contact with the road.
Buick Encore GX Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-
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292 Vehicle Care
Treadwear Indicators:Narrow bands,
sometimes called wear bars, that show
across the tread of a tire when only
1.6 mm (1/16 in) of tread remains. See
When It Is Time for New Tires 0298.
UTQGS (Uniform Tire Quality Grading
Standards)
:A tire information system
that provides consumers with ratings
for a tire's traction, temperature, and
treadwear. Ratings are determined by
tire manufacturers using government
testing procedures. The ratings are
molded into the sidewall of the tire.
See Uniform Tire Quality Grading
0 300.
Vehicle Capacity Weight
:The number
of designated seating positions
multiplied by 68 kg (150 lb) plus the
rated cargo load. See Vehicle Load
Limits 0193.
Vehicle Maximum Load on the Tire
:
Load on an individual tire due to curb
weight, accessory weight, occupant
weight, and cargo weight. Vehicle Placard
:A label permanently
attached to a vehicle showing the
vehicle capacity weight and the original
equipment tire size and recommended
inflation pressure. See “Tire and Loading
Information Label” underVehicle Load
Limits 0193.
Tire Pressure
Tires need the correct amount of air
pressure to operate effectively.
{Warning
Neither tire underinflation nor
overinflation is good. Underinflated
tires, or tires that do not have
enough air, can result in:
.Tire overloading and overheating,
which could lead to a blowout.
.Premature or irregular wear.
.Poor handling.
.Reduced fuel economy.
Overinflated tires, or tires that have
too much air, can result in:
(Continued)
Warning (Continued)
.Unusual wear.
.Poor handling.
.Rough ride.
.Needless damage from road
hazards.
The Tire and Loading Information label
on the vehicle indicates the original
equipment tires and the correct cold
tire inflation pressures. The
recommended pressure is the minimum
air pressure needed to support the
vehicle's maximum load carrying
capacity. See Vehicle Load Limits 0193.
How the vehicle is loaded affects
vehicle handling and ride comfort.
Never load the vehicle with more
weight than it was designed to carry.
When to Check
Check the pressure of the tires once a
month or more. Do not forget the
compact spare, if the vehicle has one.
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1.6 mm (1/16 in) or less of tread remaining.
SeeTire Inspection 0297 and
Tire Rotation 0297 for additional
information.
The rubber in tires ages over time. This also
applies to the spare tire, if the vehicle has
one, even if it is never used. Multiple factors
including temperatures, loading conditions,
and inflation pressure maintenance affect
how fast aging takes place. GM recommends
that tires, including the spare if equipped,
be replaced after six years, regardless of
tread wear. To identify the age of a tire, use
the tire manufacture date, which is the last
four digits of the DOT Tire Identification
Number (TIN) molded into one side of the
tire sidewall. The last four digits of the TIN
indicate the tire manufactured date. The
first two digits represent the week and the
last two digits, the year. For example, the
third week of the year 2020 would have a
4-digit DOT date of 0320. Week 01 is the
first full week (Sunday through Saturday) of
each year.
Vehicle Storage
Tires age when stored normally mounted on
a parked vehicle. Park a vehicle that will be
stored for at least a month in a cool, dry,
clean area away from direct sunlight to slow aging. This area should be free of grease,
gasoline, or other substances that can
deteriorate rubber.
Parking for an extended period can cause
flat spots on the tires that may result in
vibrations while driving. When storing a
vehicle for at least a month, remove the
tires or raise the vehicle to reduce the
weight from the tires.
Buying New Tires
GM has developed and matched specific
tires for the vehicle. The original
equipment tires installed were designed
to meet General Motors Tire
Performance Criteria Specification (TPC
Spec) system rating. When replacement
tires are needed, GM strongly
recommends buying tires with the same
TPC Spec rating.
GM's exclusive TPC Spec system
considers over a dozen critical
specifications that impact the overall
performance of the vehicle, including
brake system performance, ride and
handling, traction control, and tire
pressure monitoring performance. GM's
TPC Spec number is molded onto the
tire's sidewall near the tire size. If the
tires have an all-season tread design,
the TPC Spec number will be followed
by MS for mud and snow. See
Tire
Sidewall Labeling 0288 for additional
information.
GM recommends replacing worn tires in
complete sets of four. Uniform tread
depth on all tires will help to maintain
the performance of the vehicle. Braking
and handling performance may be
adversely affected if all the tires are not
replaced at the same time. If proper
rotation and maintenance have been
done, all four tires should wear out at
about the same time. However, if it is
necessary to replace only one axle set
of worn tires, place the new tires on
the rear axle. See Tire Rotation0297.
{Warning
Tires could explode during improper
service. Attempting to mount or
dismount a tire could cause injury or
(Continued)