Tire Size
The following illustration shows an example of a typical
passenger car tire size.
(A) 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 “70,” as shown in item “C”
of the illustration, it would mean that the tire’s sidewall
is 70% as high as it is wide.
(D) 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; 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 range and the speed rating of a tire. The load
range represents the load carrying capacity a tire is
certified to carry. The load index can range from 1 to 279.
The speed rating is the maximum speed a tire is certified
to carry a load. Speed ratings range from “A” to “Z”.
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