GMC Terrain 2025 - Tire Designations; Tire Terminology and Definitions

GMC Terrain/Terrain Denali Owner Manual (GMNA-Localizing-U.S./Canada/Mexico-18552429) - 2025
Vehicle Care 253
(7) TPC Spec (Tire Performance Criteria
S
p
ecification) : Original equipment tires
designed to GM's specific tire performance
criteria have aTPC specification code
molded onto the sidewall. GM's TPC
specifications meet or exceed all federal
safety guidelines.
Tire Designations
Tire Size
The example shows atypical passenger
vehicle tire size.
Passenger (P-Metric) Tire
(1) Passenger (P-Metric) Tire : The United
States version of ametric tire sizing
system. The letter "P" as the first character
in the tire size means a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
Ai
r 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).
Aspect Ratio : The relationship of atire's
height to its width.
Belt : A rubber coated layer of cords that
is located 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 Pressure 3255.