Firestone Tires Specifications

Harvey Firestone founded Firestone Tire and Rubber Company in 1900. Bridgestone Corporation acquired the automobile tire company from Firestone in 1988. Firestone currently offers a variety of automobile tires, including Ultra, High, Regular and All Season Performance ratings. All of these tires have specifications displayed on the storefront's sidewall, catalog, and on embossed on the tire's surface.

• First, Firestone has letters inscribed indicating the vehicle
  type. For instance, tires beginning with the letter “p” are
  designed for passenger vehicles.


• Second, these automobile tires will have a unique three-digit
  number inscribed after the initial letter. For instance, 216
  indicates the tire's width in millimeters, typically ranging between
  the low 100s and upper 200s. The aspect ratio of the tire follows
  the three-digit width. For instance, 58 would indicate the aspect
  ratio of the tire's height in regards to its width.


• Firestone tires have a construction letter, such as “R”
  for radial, which refers to the wheel's diameter of the manufactured
  tire. The two digit number that follows indicates the rim
  measurements. For instance, “12” would mean that the tire was
  manufactured to fit on a 12-inch rim.


• The tire's load index will directly follow the wheel's
  diameter and rim measurements. The tire's load index refers to the
  tire's overall capacity support. The speed rating will directly
  follow the load index number. It refers to the maximum speed that
  the tire can endure before blowing out. Each tire model has a
  different speed rating. For instance, “S” indicates that the
  tire was manufactured to withstand driving speeds of up to 112 mph.


• Lastly, the Department of Transportation (DOT) number,
  located along the tire's inside edge, certifies that the tire model
  meets federal specifications and notifies the prospective buyer
  about the tires age. The DOT number should show the week and year
  the tire was manufactured.