Tire Designations; Tire Terminology And Definitions - Buick Regal 2018 Owner's Manual

278 Vehicle Care
(6) Tire Size A combination of
:
letters and numbers define a
tire's width, height, aspect ratio,
construction type, and service
description. The letter T as the
first character in the tire size
means the tire is for temporary
use only.
(7) TPC Spec (Tire
Performance Criteria
Specification) 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 following is an example of a
typical passenger vehicle
tire size.
(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 three-digit
:
number indicates the tire section
width in millimeters from
sidewall to sidewall.
(3) Aspect Ratio A two-digit
:
number that indicates the tire
height-to-width measurements.
For example, if the tire size
aspect ratio is 60, as shown in
item 3 of the illustration, it would
mean that the tire's sidewall is
60 percent as high as it is wide.
(4) Construction Code
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; and the letter B
means belted-bias ply
construction.
(5) Rim Diameter
the wheel in inches.
(6) Service Description
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
A letter
:
Diameter of
:
These
: