The tire code, also known as the ISO metric tire code, is a combination of letters and numbers that provide essential information about automotive tires. This alphanumeric code is typically molded into the sidewall of the tire and serves to specify various details such as tire dimensions, load-bearing capacity, maximum speed, and intended use or vehicle class. The code has evolved over time, incorporating a mix of SI and USC units and additional information like ratings for traction, treadwear, and temperature resistance under the Uniform Tire Quality Grading system.
Key components of the tire code include an optional letter indicating the tire’s use or vehicle class, such as P for Passenger Car, LT for Light Truck, ST for Special Trailer, and T for Temporary (commonly used for “space-saver” spare wheels). This classification helps users identify the type of vehicle the tire is designed for.
Automotive tires are predominantly described using the ISO metric sizing system; however, some vehicles like pickup trucks and SUVs may utilize alternative systems like Light Truck Numeric or Light Truck High Flotation. Additionally, the Department of Transportation (DOT) code is an essential part of the tire code, providing further information through an alphanumeric character sequence.
The complexity of the tire code underscores its importance in ensuring safety and performance on the road. By understanding this code, consumers can make informed decisions when selecting tires that match their vehicle requirements and driving conditions. The tire code’s detailed specifications play a crucial role in maintaining optimal performance and safety standards for vehicles across different classes and usage scenarios.
Citations:
[1] https://en.wikipedia.org/wiki/Tire_code
Automotive tires are described by an alphanumeric tire code (in North American English) or tyre code (in Commonwealth English), which is generally molded into the sidewall of the tire. This code specifies the dimensions of the tire, and some of its key limitations, such as load-bearing ability, and maximum speed. Sometimes the inner sidewall contains information not included on the outer sidewall, and vice versa.
The code has grown in complexity over the years, as is evident from the mix of SI and USC units, and ad-hoc extensions to lettering and numbering schemes. New automotive tires frequently have ratings for traction, treadwear, and temperature resistance, all collectively known as the Uniform Tire Quality Grading.
Most tires sizes are given using the ISO metric sizing system. However, some pickup trucks and SUVs use the Light Truck Numeric or Light Truck High Flotation system.