Most often times I have wondered the meanings of the various numbers and letters that are usually scripted on the side of tires. I know a lot of you also wonder about it. I did a little research and will explain what they mean.

The numbers on car tire are explained using the letters and numbers printed on the side of the tire. They tell you the tires purpose, the complete dimensions, the total load/weight capacity, speed rating and more. They indicate what we call the Tire code. The code includes the tire size, radial construction, the type of vehicle the tire was made for, speed rating, and PSI inflation rating which indicates the amount of air that should be blown into it. Tire specs also include something called load rating. This is important for hauling or towing a trailer. Read below for a complete tire guide.

Tires will have something similar like this printed on the side of it: P205/60R16 90H

The first letter means type of tire for certain vehicles.
P = Passenger vehicles tire
T = Truck vehicles tire

The 3 digit number (205) is the Width. This number refers to the tire width in millimeters. It is measured in millimeters from sidewall to sidewall.

The 2 digit number (60) is the Aspect Ratio. It is the ratio of the height of the tire’s cross-section to its width. The number 60 means the height is equal to 60% of the width of the tire.

The letter (R) stands for Radial. This means the layers run radially across the tire.

The number (16) is Wheel Diameter. It is the size of the wheel measured from one end to the other. It tells you the size of the wheel that the tire is intended to fit on.

The next number (90) is the Load Index. Load Index shows the maximum load that the tire can support when inflated properly. You can also find the maximum load on the tire sidewall in both LBS pounds and KG kilograms.

The last letter (H) identifies the Speed Rating. The speed rating tells you the maximum speed capability of a tire. A tire with an H speed rating has a maximum speed capability of 210 kmph.

How to determine your tire speed rating

Here is a chart that will identify your tire speed rating. The last letter on your tire will be one of the letters below:
M = 130 kmph
N =140 kmph = Spare Tires
P = 150 kmph
Q = 160 kmph = Winter Tires
R = 170 kmph = Truck Tires
S = 180 kmph = Cars and Minivans
T = 190 kmph = Cars and Minivans
U = 200 kmph = Sport Performance Cars
V = 240 kmph = High Performance Cars
W = 270 kmph = Ultra High-Performance Cars
Y = 300 kmph = Ultra High-Performance Cars

I hope you find this piece useful, buying the right tire for your vehicles can ensure safety on our roads.

http://www.infogoons.com/2015/01/car-tire-numbers-mean/