What do the numbers and letters on the sidewall of my tires mean?
In the example P185/75R1482S the breakdown is as follows:
P = Service Type: Indicates this is a passenger vehicle tire, as opposed to a tire made for a light truck (LT) or other vehicle.
185 = Section Width: The width of the tire in millimetres from sidewall to sidewall.
75 = Aspect Ratio: The ratio of height of the sidewall to the width of the tire. This sidewall’s height is 75% of its width.
R = Internal Construction: How the plies are constructed in the tire carcass. "R" means radial, "B" means the tire is belted bias construction and "D" means diagonal bias construction.
14 = Rim Diameter: The diameter of the wheel (centre hole of the tire) in inches.
82 = Load Index: This tire has an industry-standard maximum load of 475 kg (1,047 lbs).
S = Speed Rating: This tire has an industry-standard maximum service speed of 209 kph (130 mph). Different letters correspond to different maximum service speeds.