Firestone Tire Specifications

Harvey Firestone started Firestone Tire and Rubber Company in 1900.  The Bridgestone Corporation then acquired it in 1988.  Now, this company has a variety of different tires available for you to choose from.  All of them have specifications as indicated by a code that can be found on the tire’s sidewall and in the Firestone catalog.

• Letters will be the first bit of information that is found on any Firestone tire code.  These letters tell you what type of car the tires are meant for.


• A 3-digit number refers to the tire’s width in millimeters.  This number will range from the low hundreds to the high two hundreds.


• Next, you will see the number 55.  This is the tire’s aspect ratio.  It tells you the ratio of the tire’s height to its width.


• The next number will tell you the wheel’s diameter that the tire was meant to fit on. 


• A 2-digit number refers to the tire's load index (the weight the tire was made to support).


• After the load index, you will find the speed rating.  It will tell you the maximum speed that the tire was designed for.  There will be different letters that refer to different speed ratings.


• There is also a separate number, which is known as the DOT number.  This is found along the tire’s inside edge.  It tells you that the tire meets federal specifications and it will also tell you the tire’s age.  The week and the year in which the tire was produced are part of this number.