Pontiac 2004 Bonneville - Manual (Page 339)

(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 5-67.
(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.
(G) Tire Performance Criteria Specification (TPC
Spec): 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 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.
5-63