Decoding DOT and TIN Markings: A Comprehensive Guide to Tire Compliance and Identification


The Department of Transportation (DOT) and Tire Identification Number (TIN) are essential markings found on tires, signifying compliance with regulatory standards and providing valuable information about the tire’s manufacturing details. This article will explain the significance of DOT and TIN markings on tires and how to interpret the information they convey.

  1. DOT Marking

The DOT marking signifies that a tire complies with the safety standards set by the United States Department of Transportation (DOT). All tires sold in the United States must bear this marking, confirming that they meet the minimum requirements established under the Federal Motor Vehicle Safety Standards (FMVSS). The DOT marking also serves as a starting point for the Tire Identification Number (TIN), which follows the DOT initials.

  1. Tire Identification Number (TIN)

The Tire Identification Number is a unique code that provides information about the tire’s manufacturing details. TIN is a combination of alphanumeric characters, and its structure can be divided into the following sections:

  • Manufacturer’s Plant Code: The first two or three characters after the DOT initials represent the manufacturer’s plant code, identifying the specific factory where the tire was produced.
  • Tire Size Code: The following two or three characters indicate the tire size code, which represents the tire’s dimensions and specifications.
  • Manufacturer’s Optional Code: The next set of characters, which can vary in length, is the manufacturer’s optional code. This section is used at the manufacturer’s discretion to include additional information about the tire, such as its construction, materials, or other unique features.
  • Date of Manufacture: The final four digits of the TIN denote the tire’s production date. The first two digits represent the week of production, while the last two digits indicate the year. For example, a TIN ending in “3721” means the tire was manufactured during the 37th week of 2021.

It is essential to note that TINs for tires produced before the year 2000 have a slightly different format. In this case, the date of manufacture is represented by three digits, with the first two indicating the week and the last digit representing the year within the decade. However, this format can create confusion when trying to determine the exact production year.

  1. Importance of DOT and TIN

Understanding the DOT and TIN markings on tires is crucial for several reasons:

  • Compliance: The DOT marking ensures that the tire complies with the safety standards set by the U.S. Department of Transportation, providing peace of mind for consumers.
  • Manufacturing Details: The TIN allows consumers to identify the manufacturing plant, tire size, and production date, which can be useful when purchasing new tires or when addressing potential tire recalls.
  • Tire Age: Knowing the tire’s production date can help consumers determine its age, which is crucial for evaluating tire performance and safety. Tires can deteriorate over time, even when not in use, so it is generally recommended to replace tires that are six to ten years old, regardless of their tread depth.

The DOT and TIN markings on tires provide essential information for consumers and serve as indicators of compliance with safety standards. By understanding these markings, consumers can make informed decisions about tire purchases and better assess their tire’s age and manufacturing details, contributing to improved vehicle safety and performance.

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