Chevrolet 2007 Optra Owner's Manual page 306

(B) Tire Ply Material: The type of cord and
number of plies in the sidewall and under the tread.
(C) Tire Identification Number (TIN): The Tire
Identification Number (TIN). The TIN shows
the manufacturer and plant code, tire size, and
date the tire was manufactured. The TIN is molded
onto both sides of the tire, although only one
side may have the date of manufacture.
(D) Maximum Cold Inflation Load
Limit: Maximum load that can be carried and
the maximum pressure needed to support
that load. See Compact Spare Tire on page 334
and Loading Your Vehicle on page 236.
(E) Tire Inflation: The temporary use tire or
compact spare tire should be inflated to 60 psi
(420 kPa). For more information on tire pressure
and inflation see Inflation - Tire Pressure on
page 311.
(F) 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.
306
Tire Size
The following illustration shows an example of a
typical passenger car 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.