How To Read Tire Size? - The Most Detailed Guide

Sep 16, 2022

Have you known how to read a tire size? Tire is such a significant factors affecting your riding experience. Let's dive right in!

Car tire parameters are an important basis to help you choose the right type of tire when you need to replace, repair, avoid damage that causes unsafety during travel. Normally, each respective car model uses a specific type of tire, suitable for performance. Through the information shown on the tire, users can easily read important parameters without spending much time. So how to read tire size? What is the meaning and interpretation of these parameters?

Tire functions

how to read tire size

Car tire

  • Tires bear the entire weight of the vehicle.
  • Because it is the surface in direct contact with the road surface, it controls departure, stop, turn, acceleration, and deceleration.
  • Tires reduce impact when traveling on rough roads.

How to read the size of a tire?

1. Manufacturer name and tire name

Observing the letters and parameters of the car tires helps the user to accurately capture all the important information. Tire names can consist of letters alone, or a combination of letters and numbers, in large font sizes, usually on the outer ring.

tire size

Tire specs meaning

2. Service description features

Not all tires have a service symbol, if any, this sign is usually located on the side of the tire (in front of the tire name), specifically the meaning of the symbols is as follows:

  • P: type of tire for passenger car (Passenger vehicle).
  • LT: tire for light truck (Light Truck).
  • ST: special trailer tires (Special Trailer).
  • T: type of temporary replacement tire (Temporary).
  • C: tires for commercial vehicles, heavy trucks.

3. Tire width and profile

When observing a car tire, you will surely see the following parameters:

  • Width is a series of letters and numbers placed after the service specification and with a slash in the middle. The first three numbers are the tire width, in mm, this value ranges from 155 - 315.
  • Tire profile is the next two numbers after the width and after the slash. This is the ratio of the tread width to the sidewall height.

tire specs

Parameters of car tires in terms of width and tire profile

For example, 90/80 tire size meaning is:

  • The width of the tire is 90mm
  • The percentage of tire height to the width of the case is 80%, i.e. the height of the tire will be 0.8x90 = 72mm
  • The diameter of the motorcycle wheel rim is 17 inches.

4. Tire structure

Normally, the tire construction parameters are shown with the letter R, located immediately after the tire profile. The letter R stands for Radial radial steel structure - this is one of the industry standards for passenger cars. When looking at other vehicles, you may come across the letters B, D or E.

5. Wheel diameter

Car tire specifications show the diameter of the rim located right behind the tire structure. Based on this size, the technician will choose the right tire during the replacement process.

tire specification

The rim diameter 19 is right after the tire specifications for the R structure

6. Maximum permissible load rating

This parameter indicates the load capacity of the tire, the larger the value, the higher the load of the tire. Users should note, never replace the original tire with a tire with a maximum allowable load index lower than this parameter, only use tires of the same or higher. This will ensure that the tires can withstand the maximum load of the vehicle when operating.

According to the picture, the maximum load of a tire is 111. Therefore, when replacing wheels, only tires with an index of 111 or higher should be used.

7. Maximum allowable speed indicator

The last number in the tire size information series is the speed index, represented by the letter: P225/70R16 91S. Just as the load rating corresponds to a specific load mass, the letter of the speed index corresponds to the maximum speed based on standard tests.

For example, tires with a speed rating "R" will withstand speeds up to 106 mph, while tires with an "W" rating will withstand speeds up to 270 mph (Note: This is not a recommended driving speed. You should follow the maximum allowed speed limit on the road.)

8. Heat resistance index

If you see the letter A, B or C on the tire located in the inner part of the tire, the tire's high-speed heat resistance will correspond. In which, the index C represents the lowest heat resistance, A is the highest.

9. Tire pressure indicator

This number is located on the inner edge of the tire, indicating the right pressure to maximize tire performance. According to the illustration, the tire pressure reading has a value of 50 PSI.

tire specs

Specifications on PSI car tires show tire pressure index


Thus, just by observing and understanding the correct tire parameters, customers can know how to read tire size and understand most information related to tires, making the process of choosing tires when changing wheels easier and faster.

You can also take your car to the brand warranty and maintenance service center for repair, replacement and dedicated advice on how to care for and maintain your vehicle.

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