EXAMPLE : P255/60R17 102 V
Width of the tire is 255mm.
The aspect ratio of the tire is 60%. The tire's sidewall height from the edge of the wheel to the tire's tread is 60% of the width.
This letter is for how the tire is constructed. Radial is the standard construction method for almost all tires.
The tire is designed to be mounted on an 17" wheel diameter.
This number is the load index. Ranging between 71 and 110 a higher number means the tire can carry more weight.
71 = 761lbs 110 = 2337lbs
This letter is the speed rating of the tire.
There are two ways that tire manufacturers display tire size, inches and metric. How to read tire size in inches is very straight forward.
Example A : 33X12.50R15
The first number is your overall diameter of the tire. In this example the tire diameter or "height" is 33 inches tall. The second number represents the width of the tire. In most cases with inch measurement tires the width will have a .50 decimal after the initial number. In example "A" this reads 12.50, meaning the tire width is 12 and 1/2 inches. The final number simply is the wheel size or "diameter" of the wheel that the tire will fit on.
How to read tire size with a metric measurement is a little more difficult and usually takes a calculator to get exactly right.
Learn About Tire Sizes
Example B : 285/75R16
On metric tires the first number is your width of the tire in millimeters. In example "B" this reads 285mm. There are 25.4 mm in one inch. To convert 285mm to inches you divide 285mm by 25.4 to get 11.22in. So your width of a 285mm tire is 11.22 inches. The next number then represents the percentage of the width (285mm or 11.22in) that is the sidewall measurement of the tire. In this example the side wall measurement of the tire would be 75% of 11.22in which is 8.41 inches or "214mm". To then get the overall diameter or "height" of the tire you would add the two sidewalls and the diameter of the wheel. In example "B" the last number "16" is the wheel size the tire will fit on. Therefore the sidewall twice would be 8.41 x 2 = 16.82 plus the wheel "16" makes the tire height 16.82 + 16 = 32.82. So a 285/75R16 metric tire would calculate to an inch measurement tire of 32.82X11.22R16. Remember, not all tire sizes are manufactured in both metric and inch sizes so learning how to read tire size can be a valuable tool for anyone in the market for new tires.