Dodge 2010 Ram Truck Owner's Manual page 402

400 STARTING AND OPERATING
Tire Sizing Chart
Size Designation:
P = Passenger car tire size based on U.S. design standards
....blank.... = Passenger car tire based on European design standards
LT = Light truck tire based on U.S. design standards
T = Temporary spare tire
31 = Overall diameter in inches (in)
215 = Section width in millimeters (mm)
65 = Aspect ratio in percent (%)
— Ratio of section height to section width of tire
10.5 = Section width in inches (in)
R = Construction code
— R means radial construction
— D means diagonal or bias construction
15 = Rim diameter in inches (in)
EXAMPLE:
I n f o r m a t i o n P r o v i d e d b y :