2. DIMENSIONS—TRUCK TIRES

ASPECT RATIO

OVERALL DIAMETER
The measurement of the distance of an unladen tire from tread surface to tread surface on opposite sides of the tire.

OVERALL WIDTH
Measurement of the cross section of an unladen tire including ribs and protrusions. Usually the same as section width on radial tires.

SECTION WIDTH
Measurement of the cross section of an unladen tire across the casing only—not including ribs or protrusions.

TREAD WIDTH
Distance across the tread face of an unladen tire.

TREAD DEPTH
Distance from tread surface to major groove base at designated measuring point.

SECTION HEIGHT
Distance from the bead seat to the tread surface of an unladen tire.

RIM WIDTH
Distance between the rim flanges.

NOMINAL RIM DIAMETER
Diameter of the rim from bead seat to bead seat in inches.

STATIC LOADED RADIUS
Distance from the center of the axle to the ground of a loaded tire under maximum dual load and inflation as stamped on the sidewall of the tire.

LOADED WIDTH
The maximum section width of a loaded tire under maximum dual load and inflation as stamped on the sidewall of the tire.

MINIMUM DUAL SPACING
The minimum allowable distance between the wheel center lines in a dual arrangement.

REVOLUTIONS PER MILE (RPM)
The number of tire revolutions in one mile measured at a speed of 55 mph at maximum dual load and inflation as stamped on the sidewall of the tire.

All dimensions measured following a 24-hour inflation period.