Aspect Ratio
(Section Height/Section Width) X 100
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 Section 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 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.
Tire cutaway diagram