Outer diameter
The diameter of a new, properly inflated tire.
Overall width
Total width measured at the exterior sidewalls of an inflated tire, including the additional width of
labeling, decorations, or protective bands or ribs.
Passenger car tire
A tire intended for use on passenger cars, multipurpose passenger vehicles, and trucks, that have a
gross vehicle weight rating (GVWR) of 10,000 pounds or less.
Ply
A layer of rubber-coated parallel cords.
Ply separation
A parting of rubber compound between adjacent plies.
Pneumatic tire
A mechanical device made of rubber, chemicals, fabric, and steel or other materials, that, when
mounted on an automotive wheel, provides the traction and contains the gas or fluid that sustains the
load.
Production options weight
The combined weight of installed regular production options weighing over 5 lbs (2.3 kg) more then the
standard items they replace, and not previously considered as curb weight or accessory weight. These
include, for example, heavy-duty brakes, ride levelers, heavy-duty battery, and special trim.
Radial ply tires
A pneumatic tire in which the ply cords that extend to the beads are laid at substantially 90 degrees to
the centerline of the tread.
Recommended inflation pressure
The tire pressure recommended by the vehicle manufacturer for a tire of a specified size that has not
been driven for more than a couple of miles (kilometers) at low speeds in the 3 hour period before the
tire pressure is measured or adjusted.
Reinforced tire
A tire designed to operate at higher loads and at higher inflation pressures than the corresponding
standard tire.
Rim
The outer edge of a wheel upon which the tire beads are seated.
Rim diameter
The nominal diameter of the wheel's tire bead seating surface. If you change your wheel size, to
wheels of a different diameter, you will have to purchase new tires to match the new wheels.
Rim size
Designation means rim diameter and width.
Rim type designation
The industry or manufacturer's designation for a rim by style or code.
Rim width
The nominal distance between wheel rim flanges.
Vehicle maximum load on the tire
The load on an individual tire that is determined by taking each axle's share of the maximum loaded
vehicle weight (GAWR) and dividing by 2.
Vehicle normal load on the tire
The load on an individual tire that is determined by taking each axle's share of the curb weight,
accessory weight, and normal occupant weight (distributed according to the table below) and dividing
by 2.
Wheel size designation
Wheel rim diameter and width.
Occupant loading and distribution for vehicle normal load for various designated seating
capacities
Designated seating capacity,
number of occupants
Vehicle normal load, number
of occupants
Occupant distribution in a
normally loaded vehicle
2, 3 or 4 2 2 in front
5 3 2 in front, 1 in back
Applicable only in the United States and Canada
Tires and vehicle load limits
