Understanding Tire’s DOT Code And Its Importance

The DOT code is a Tire Identification Number (TIN) imprinted on the sidewall of your tires. The DOT code indicates the tire manufacturer's compliance with the Department Of Transportation (DOT) National Highway Traffic Safety Administration (NHTSA) in the United States. This code comprises letters and numbers that allow you to know the manufacturing location, tire size code, week, and year the tire was manufactured. Most importantly, it indicates that the tire has passed the testing and manufacturing requirements dictated by the NHTSA. According to the regulations, the tire identification number must begin with the letter DOT, followed by various characters. The DOT code was designed by the NHTSA to make it easy to recall tires and maintain the records of their production dates. These codes are also helpful for the consumer to determine the age of a tire. Often new tires come with a DOT card, so you can record the numbers of your tires and send them to the company. Alternatively, you can register your tires with the manufacturer online on their website.

Let's consider a tire that has a DOT code ATL2U4AVA1520. The first two or three letters - ATL - are assigned plant code and they indicate where the tire was produced. In this case, ATL is the code assigned to the W Tire Company in Atlanta, Georgia. The next letters - 2U - are size codes. Then the letters - 4AVA - are the tire type codes based on the construction and are assigned by the manufacturer. Most importantly, the last four digits 1520 are the date code of the tire. The last four numbers mean that this tire was made in the 15th week of the year 2020. The last four digits are of prime importance as they indicate the manufacturing time and help you identify how old the tire is.

However, some tires that were produced before the year 2000 had 3-digit numbers at the end of the DOT codes. On those tires, the last digit dictated the year, but it was tough to figure out the decade. Therefore, after the year 2000, the fourth digit was added to the DOT code. Furthermore, legislation passed in 2015 transitioned the factory code from two to three characters, which pushed the DOT code to 13 characters in length. Now all new tires have DOT codes that follow the same standard of 13 characters. This rule has been in effect since April 13, 2015.

The DOT code is used to register your tire with your name and address with the manufacturer. This helps the tire manufacturer to contact you in case of recall and warranty claims. The DOT code also helps you identify the age of your tire. When you purchase a new tire, it doesn't necessarily mean that it has been manufactured recently. Often it takes a while to reach the retailers after being shipped from the company. Supply chain problems and other factors can sometimes delay the time when the tire reaches the dealer's point or the retail shop. Some retailers stock them for a long time and the DOT helps you to determine how old the tire is from its date of manufacturing. 

After the tires are manufactured, they move from industries to warehouses and to storage facilities from where they are dispatched further. Improper care, long storage, and exposure to weather conditions can deteriorate the rubber on the tires. It can also lead to premature aging, which can accelerate due to poor storage conditions. However, there are a few measures that can be used to protect the tires. Some of them are as follows:

• Protection from UV rays, prolonged exposure to sunlight, or excessively high temperatures.

• Keep the tires vertically in a perfectly stress-free orientation. Racks can be used for storing tires for a long time.

• Protect the tires from moisture and humidity by storing them in ventilated or air-conditioned rooms.

• Store the tires at room temperatures with proper protection from freezing temperatures during winters.

While factors like high temperatures, moisture, and sunlight are the main contributors to excessive tire aging, it would still take a lot of time for your tires to show some signs of aging. Tires are manufactured to be durable and they can sustain a long shelf life under proper protection. Whitening of rubber and shallow hairline cracks are some signs of aging that can develop due to prolonged UV exposure and heat. If your tires are showing these signs in the first few years, you should get them replaced. To prevent such an issue, it is necessary to purchase good-quality tires for your vehicle.

• It's a misconception that the number mentioned in the DOT code states when the tire was approved. On the contrary, the number states the time of manufacturing and not the date of approval by the Department Of Transportation. The DOT symbol itself is an indication that the tire has been already approved.

• Another belief amongst car enthusiasts is that one should purchase a tire with the DOT code of the current year. As long as the tires are stored properly, they will be in excellent condition and can be used even if the tire is a couple of years old.

  
  

A consensus amongst various tire manufacturers and associations is that tires usually have a useful service life of five to six years from the time it is manufactured. But several studies by the NHTSA indicate ‌the tires should be verified for expiration after the fourth year. The tire aging process begins regardless of whether the tires are installed on the vehicle or not. Tire aging is a hidden hazard that can often go unnoticed because the customers are unaware of the DOT code and it is difficult to decipher. 

With increasing developments and advancements in tire manufacturing, the tread life has significantly increased with some tires sold with a promise of 100,000 km of tread life. As tread life becomes less of a concern, the rubber oxidation and aging factors of tires need more attention. Usually, tire treads wear out way before your tires will expire due to age. There can be some exceptions like show cars and classic vehicles which are used rarely. Don't forget the spare tire, which is often not replaced over a long time.

Various experts have different guidelines on how to determine when the tire is too old to be safe, Generally, if your tires are five years or older, consider replacing them for safety reasons. Many manufacturers have taken small steps to warn customers by placing the warnings in the owner's manual, which helps them to make sensible decisions. On the positive side, buying new tires will help you improve driveability, handling and prevent sudden tire failures. It's important to carry out proper tire care and maintenance to ensure your tires last longer. If you need all the right information to make an informed decision while purchasing a new set of tires, you can refer to your comprehensive tire buying guide.