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What Do the Numbers on a Tire Mean?


Many car owners ask the question, “What do the numbers on my tires mean?” There is a lot of information printed on the side wall of every tire. This week, we’ll be examining an often overlooked set of tire number meanings.

Your tire’s birth date or “tire birthday” is the approximate time that the tire was manufactured, and it's very important information to know when it comes to maintaining your vehicle. Read on to learn more about your tire’s numbers.

Locating and Reading the Birth Date

The tire birth date is not really a specific date, but rather the week and year the tire was manufactured. You can find it by locating a set of numbers that begins with “DOT." This string of letters and numbers will end with 3 or 4 numbers. For instance, your tire’s numbers might read DOT DA07 JN2S 4212. That last number, 4212, is the “birthdate”.

The first half of the numbers, “42," indicates that the tire was made in the 42nd week of the year. The second half of the numbers, “12," indicates that the tire was made in 2012. Thus, this particular tire would have been made in the 42nd week of 2012, or about mid-October 2012.

Note: Some older tires only have three numbers; the first two are the week number, and the last one is the last digit of the year (so, 324 would be the 32nd week of either 2014, 2004, 1994, etc. That can make it kind of tricky!).

Why are Tire Birthdays Important?

Tire birthdays are important because they allow you to estimate how old a tire is. This can come in handy especially when dealing with tires that you didn’t purchase (or don’t remember when you purchased them). It’s important to know how old a tire is because experts recommend discarding tires that are 10 years old or more, regardless of how new they might appear to be. Tires can deteriorate or rot in storage without even being used. Some manufacturers suggest discarding tires 6 years from the tire birth date.

If you're searching for a used car, check how old the tires are using that printed tire "birthday." That way, you can change the tires out if they are too old, or choose a model with newer tires, which will increase your safety on the road.

Shopping for new tires? You can usually request newer tires if you feel that the ones you received have too old of a birth date.

How Often Should You Change Your Tires?

Besides the 6-10-year expiration date, you should change your tires frequently to prevent safety hazards caused by a loss of traction (tread loss), tire pressure issues, or a flat tire. There is no set time period to change your tires, as every tire and every driver is different. Experts recommend changing tires every 25,000 to 50,000 miles. Some factors that might affect tire wear (and therefore how often you should change them) include:

  • Driving frequency
  • Heavy braking
  • The type of road surface you’re driving on
  • Poor maintenance of the vehicle (can put additional strain on tires)
  • Overloading the vehicle with weight or cargo
  • The type of tire being used
  • Climate (tires don’t last as long in areas with hot, dry weather)

For quick reference, try the penny test to check if your tire treads are still good. However, as mentioned, knowing the tire birth date makes things a lot easier when it comes to tire maintenance.

High-quality tires are very important for auto performance and safety. If you need expert attention or tire replacements, stop by Convoy Auto Repair, San Diego’s favorite auto repair shop. We offer complete car check ups at regularly scheduled intervals. These include tire inspections to keep your car running in tip-top shape. Get in touch today!


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