Tire Dimensions & Measurement Definitions

ASPECT RATIO = Section Height  xl00 
                             Section Width  

DEFLECTION = Free radius minus loaded radius.  

FREE RADIUS = The radius of the tire/wheel assembly that is not deflected under load. 

LOADED RADIUS = Distance from wheel axis of rotation to supporting surface at a given load and stated inflation pressure. 

LOADED SECTlON HEIGHT = The loaded radius minus half of the nominal rim diameter. Distance from rim seat to outer tread surface of a loaded tire. 

NOMINAL RIM DIAMETER = Diameter of rim seat supporting the tire bead. Examples: 13", 15" and 16.5".  

OVERALL DIAMETER = The diameter of the inflated tire without any load.  

OVERALL WIDTH = Maximum width in cross section of unloaded tire including protruding side ribs and decorations. 

REVOLUTIONS PER MILE = Measured number of revolutions for a tire traveling one mile. This can vary with load and inflation. 

RIM WIDTH = Linear distance between rim flanges in contact with the tire. 

ROLLING CIRCUMFERENCE = The linear distance traveled by a tire in one revolution. This can vary with load and inflation. Rolling circumference can be calculated as follows: 63,360 divided by revolutions per mile = rolling circumference in inches.

SECTION HEIGHT = Distance from rim seat to outer tread surface of unloaded tire.  

SECTION WIDTH = Linear distance between the outside sidewalls of an inflated tire without any load (exclusive of protruding side ribs and decorations). 

TREAD WIDTH = The portion of the tread design which comes in contact with the road.