Understanding Tire Numbers and Letters: A Guide for Drivers

By: Anas Assaf

February 22,2018

2 min read

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Introduction

Many of us have wondered about the meanings of the numbers and letters printed on our car tires. Today, we will clarify what each number and letter signifies, enabling you to determine the right tire for your vehicle that aligns with the driver’s manual provided with the car.

As illustrated in the image above, there are multiple sections of numbers and letters. We will reference the image to explain each part of these specifications.

Understanding Tire Elements

Tire Type and Width (Tire Type / Width)

The letter P indicates the type of tire designed for passenger vehicles. Sometimes, this letter may be absent, as some tires are suitable for nearly all daily use. The numbers next to the letter (185) represent the tire's width in millimeters, which is "185 mm".

Aspect Ratio (Aspect Ratio)

The number shown in the image (75) indicates the aspect ratio, which refers to the height of the tire's sidewall as a percentage of its width. A ratio of 75% signifies that the tire's height is 75% of its width. The higher the ratio, the larger the sidewall of the tire.

Radial Diameter (Radial)

The information about the tire's diameter consists of two parts: the letter R and a number. The letter signifies Radial, meaning radial construction, while the number (14) indicates the wheel's diameter in inches. This means that the wheel fitted with the tire in the image has a diameter of 14 inches.

Load Rating (Load Rating)

The number next to the wheel diameter (82) indicates the amount of weight the tires can safely carry under normal conditions, considering the air pressure within the tire. The number 82 denotes that the tires can support a load of 475 kg. It is advisable not to purchase tires with a load index lower than that of the tires previously used on the vehicle. (See the image)

Speed Rating (Speed Rating)

The last letter on the tire indicates the maximum speed the tire can handle safely. The letter S signifies that the tire can withstand speeds of up to 180 km/h safely. (See the image)

Additional Notes

Some tires may also include other numbers and letters that indicate various specifications, such as the year of manufacture or suitability for snow or off-road conditions. However, the information provided here is what you need to know for your daily driving and city or highway use.