Tire & Wheels Measurements
What do all the numbers mean?
P – Passenger Vehicle Tire
LT – Light Truck
T – Temporary (Spare Tire)
The first digits on the tire’s measurements indicate width of the tire in millimeters (mm). It is measured from sidewall to sidewall.
This number indicated the height of the tire, from the bead to the top of the tread.
This is described as a percentage of the tire width. In our example, the aspect ratio is 75, so the tire’s height is 75 percent of its width, or 176.25 mm ( .75 x 235 = 176.25 mm, or 6.94 in).
The smaller the aspect ratio, the wider the tire in relation to its height.
High performance tires usually have a lower aspect ratio than other tires. This is because tires with a lower aspect ratio provide better lateral stability. When a car goes around a turn lateral forces are generated and the tire must resist these forces. Tires with a lower profile have shorter, stiffer sidewalls so they resist cornering forces better.
The R designates that the tire was made using radial construction. This is the most common type of tire construction. Older tires were made using diagonal bias (D) or bias belted (B) construction. A separate note indicates how many plies make up the sidewall of the tire and the tread.
This number specifies, in inches, the wheel rim diameter the tire is designed for.