What the Numbers on your Tire mean
The numbers on a tire can be made confusing, but let's look at it in simplistic terms. Begin with the numbers themselves, there may be letters inserted in between these but just look for the string of numbers like this : P 205/65/16T 89S. The 205 is the width of the tire in millimeters. 65 is the "profile" or the height of the sidewall from the bead to the shoulder of the tread. The 65 actually means the sidewall is 65% as tall as the tire is wide in millimeters. The last number is the size of the rim in inches. The 89 at the end is the load index number. This is a rating scale of the amount of load a single tire can carry.
WHAT ABOUT THOSE LETTERS?. First, you'll see either a P or and LT. The P on your tire makes it a passenger tire, generally found on cars, these are standard 4 ply thick tires without reinforced sidewalls. The LT on your tires makes them light truck tires. These will have a reinforced sidewall and a load rating at the end of the string of numbers. Either load range C(6 ply), D(8 ply), or E(10 ply). The ply is the number of steel and nylon belts wrapped around the tread part of the tire. The more "ply's" a tire has, the greater carrying capacity of the tire.
THE LETTER THAT FOLLOWS THE RIM SIZE? The letter that either follows, or sometimes is before the rim size are your speed ratings. Speed ratings on tires are used to classify the tires maximum speed it can handle over long distances These letter ratings in order are:S,T,H,V,Z,W,Y. In a size such as; 225/55/ZR17 89Z, the ZR means that the tire is in the Z,W,Y range of speeds, and the 89Z shows that they are in fact Z speed rated tires. Speed ratings are to be equal or greater than what the car came with.
This is the easiest way to understand the numbers on the side of a tire. To learn more about modifying the tires to achieve better driving look for more articles on tires.
