Tires' measurements
Section width is the first number in the tire marking. For example, 195/50 R16. In this case, the section width stands for 195. The linear distance between the outsides of the two sidewalls of an inflated tire. Expressed in millimeters.
Aspect Ratio (profile height) is the second number in the tire marking. For example, 195/50 R16, where 50% is for height size. The ratio of tire height to width is expressed as %.
Wheel diameter is the third number in the tire marking. For example, 195/50 R16, with a rim size 16. It must match with the diameter of the wheel. Expressed in inches.
Wheels' measurements
Rim diameter (D) is the diameter of the wheel rim, expressed in inches.
The number of holes (LZ) is the number of the lug holes on the wheel.
The Pitch Circle Diameter (PCD) is the circle's diameter that passes through the center of all the studs.
Rim width (RW) is a wheel width expressed in inches.
ET indicates the distance between the mounting surface and the geometric center of the wheel (the symmetry axle).
DIA is the diameter of the central hole for the column.