10-52 Vehicle Care
Tire Designations
Tire Size
The following is an example
of a typical passenger vehicle
tire size.
(A) 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.
(B) Tire Width
: The three‐digit
number indicates the tire section
width in millimeters from
sidewall to sidewall.
(C) 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 C of the illustration, it would
mean that the tire's sidewall is
60 percent as high as it is wide.
(D) Construct ion 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; and the
letter B means belted‐bias ply
construction.
(E) Rim Diameter
: Diameter of
the wheel in inches.
(F) 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.
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