Are the DOT numbers on tires important?

The DOT numbers that you find on the sidewall of a tire are a series of letters and numbers (typically 10-13) that are a legal requirement by the Department of Transportation (DOT) and provide pivotal information about the tire. The numbers explain where and when the tires were manufactured and that they meet the safety compliance of the DOT. Typically, the most important part is the last four digits which contain the week and year of manufacture.

Here is a breakdown of what all the letters and numbers mean:

DOT Prefix: The letters "DOT" confirm that the tire meets U.S. Department of Transportation safety standards.

Manufacturer and Plant Code: The next two characters identify the factory where the tire was made.

Tire Size Code: The following characters indicate the tire size.

Brand-Specific Information: The next few characters are unique to the tire manufacturer and model.

Date Code (Last Four Digits): The last four digits show the week and year the tire was manufactured, for example, 4219 means the tire was made in the 42nd week of 2019.

This date code is crucial for determining the age of the tire, as tires older than six years may become unsafe due to rubber degradation, even if they have good tread. If the tire was made before the year 2000, it may have only a three-digit date code, which is now outdated and considered unsafe for use. As a general rule, tires typically last between three to six years or 25,000 to 75,000 miles, depending on factors like tire quality, driving habits, road conditions, and maintenance.  For optimal safety,  if tires are more than five years old, have driven more than 50,000 miles, or the tread depth reaches 2/32 of an inch, it's time to replace them.

What situations will require you to know the DOT number?

You would need to check the DOT numbers on your tires in several situations, including:

Checking Tire Age: Tires degrade over time, even if they look fine. If your tires are over six to ten years old, you should consider replacing them, regardless of tread depth.

Buying Used Tires: Always check the DOT code to ensure you're not buying old or potentially unsafe tires.

Recalls & Safety Alerts: If a tire manufacturer issues a recall, they will reference the DOT number range affected. You can compare this with your tires to see if they need to be replaced.

Ensuring Compliance: If you're driving in areas with tire safety regulations, such as commercial trucking, authorities may check DOT numbers to ensure compliance.

After an Accident or Blowout: If a tire fails unexpectedly, checking the DOT number can help determine whether age or manufacturing defects played a role.

How do you locate your DOT number?

You can locate the DOT number on your tires by checking the sidewall. Here’s how to find it:

1. Look for the letters "DOT". The series always begins with DOT, followed by a combination of letters and numbers.

2. Check both sides of the tire. The full DOT number (including the date code) is often on the inside sidewall of the tire. The outer sidewall may only show a partial DOT code.

3. Use a flashlight if the DOT is hard to see, or slightly turn the steering wheel to expose the sidewall better. 

4. Once you've located the DOT number, make sure to take a photo of it or write it down somewhere you can quickly locate it if needed in the future.

While you don't need to memorize your DOT number or use it on a regular basis, it's good to have a general idea of how to locate it should you need to when assessing the safety or age of your tires. To watch a visual guide on how to find the DOT numbers, check out the video below.

For more information on routine safety checks, read the following blog:

Checklists for Safe Driving in Every Season

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