If you take a good look at any tire, you'll spot a stamped DOT number. This number is like a secret code that holds important info about your tire's safety. But let's be honest, it's not always crystal clear to drivers what that DOT number is trying to say. That's where our team at our tire store in South Austin comes in to tell you how to decode a DOT number.

DOT

Each tire identification number initiates with the acronym DOT, signifying Department of Transportation compliance. This designation serves a dual purpose, confirming that the tires adhere to the Department of Transportation's stringent regulations and providing a standardized foundation for the tire's tire identification number (TIN).

Manufacturer’s Identification Mark

The Tire Plant Code is the manufacturer's identification mark. Those two characters are like a special code for the tire's birthplace. Every tire factory has its own unique combo, usually a number and a letter. But why does it matter? Well, if there's ever a tire recall, safety hiccup, or any tire trouble, they can track it back to the specific factory where the tire was made.

Tire Manufacturer Characteristics

The third set of values in the DOT number is where manufacturers can add their own unique touches or specific details about the tire. According to the US Federal Register, "Manufacturers can use this third grouping to share any other important details about the tire, but it's not mandatory unless they're making tires for someone else's brand."

But just like the tire size code, this grouping doesn't usually give drivers much useful info. It's more for handling recalls, sorting out mistakes, and official ID purposes.

Tire Size Code

The next pair of numbers or letters is your tire size code, but it's not as straightforward as it sounds. In the past, the National Highway Traffic Safety Administration (NHTSA) had a standard list of tire sizes with two-digit codes to represent them. But now, thanks to the DOT, manufacturers get to create their own size code, as per the US Federal Register. This change was meant to simplify things for manufacturers when they make new tires without waiting for NHTSA updates.

Tire Age

Even if your tires haven't hit the road, they can still go bad over time. Once they reach the 5-year mark, tires start to experience something called thermo-oxidative degradation – it's like a chemical reaction that can mess with their roadworthiness.

To figure out how old your tire is, just check out the last four digits in your DOT number. The first two numbers show the week it was made in the year, and the last two tell you the actual year. For instance, if your DOT ends with 3020, your tire was born in the 30th week of 2020. You can dig deeper into the tire age in our full guide here.

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