Decoding your Tires

What your Tire Sidewall is Trying to Tell You
To get the right tire for you, first you need to understand what the information on the sidewall is telling you.
For most of us, the information on a tire wall is a foreign language – indeed the chances are you haven’t even noticed there’s anything there. However, if you can decode those numbers, dashes and letters, you’ll uncover a surprising amount of information such as where it was made, its size and even how it complies with U.S. regulations.
The first and most obvious will be the tire brand name, but there’s plenty that will need decoding.
At the top of a tire you’ll find a long number separated by a slash. Those numbers before the slash tell you the width in millimetres across the top of the tire. This can also be known as the section width.
Before this you sometimes see a letter – this tells you the type of work the tire is designed for. The letter P for example, means the tire was designed to work on normal passenger cars.
After the slash comes a two-digit number. This is the aspect ratio of the sidewall and refers to its height versus the width of the tire. Imagine you have a figure of 40. This would mean the sidewall is 40% the width of the tire.
You will then see a letter refers to the tires construction. Almost all tires sold today have R – this stands for radial construction. You might also see D for bias-ply tires and B for belted.
Finally, this letter will be followed by a number which explains the diameter of the wheel that the tire can fit.
Beyond this number you see what’s called the service description. This describes the load a tire can bear and how fast it can go. It starts with a number. For example, 93 stands for 650 kilograms. This is followed by a letter which denotes the maximum speed it can handle. For passenger cars these letters start at Q which mean 99mph and reaches as high as Y which is good for 186mph.
Elsewhere you will find the following:
• The ECE approval mark and number: This tells you that the tire conforms to the United Nations Economic Commission for Europe.
• Tire pressure information: This is the maximum pressure you can pump the Tire up you. Have a look in your vehicle’s manual for more information on maximum pressures – in some cases this can have an impact on your handling.
• Tread wear indicators: All cars will have tread wear indicators. They tell you when a Tire is becoming too worn and needs to be replaced. Keep an eye on these – worn Tires can be extremely dangerous to drive on.
• Production date: A four-digit code will tell you the month and year your Tire was constructed.
There is, therefore a huge amount of information waiting for you just there on the side of your Tire. Once you know what it means it can help you select the very best Tires for you and your needs.