How to Read Tire Information

February 13th, 2015

Learn how to read tire information on the side of your car’s tires.

Before you replace the tires on your car, you need to at least know the size and speed rating of the tires. Fortunately this information is embossed on the side of tires, and below we show you how to read these details. Once you have this information, have a look at the tires we stock, then visit your nearest store to have your new tires installed.

The tire information may start with a letter or two, which identifies the type of vehicle suited to the tire. The letter ‘P’ means our example tire is suitable for a passenger car. If the tire information does not start with letters, it is probably a car tire.

The first number indicates the width of the tire. Generally the measurement is shown in millimeters, though four-wheel drive tires sometimes show width in inches. Our example tire has a width of 205 millimeters.

The second number indicates the height of the tire as a percentage of its width. (This value is often referred to as the ‘aspect’ of the tire.) Our example tire has an aspect of 60, which means the tire’s height is equal to 60% of its width.

The letter after the height value indicates the construction used within the tire’s casing. Our example tire uses radial (‘R’) construction, while other tires may use belted bias (‘B’) or diagonal bias (‘D’) construction.

The number after the construction value shows the diameter of the wheel rim suited to the tire. Generally the measurement is shown in inches. Our tire is suited to a 15-inch rim.

The first number after the tire size is the load index of the tire. By referring to a separate load-index chart, the index value allows us to determine the how much weight the tire can support.

The final letter provides the speed rating of the tire, which is the maximum speed the tire has been designed to handle. The table below shows the some common speed rating values, where we see that our example tire is designed to handle a maximum speed of 130mph.

Speed
Symbol
Speed
(mph)

(km/h)
P 94 150
Q 100 160
R 106 170
S 112 180
T 118 190
U 124 200
H 130 210
V 149 240
W 168 270
Y 186 300
Z 186+ 300+
  Tags: tires, auto repair
  Posted in: Tire 101