Knowing how to check your tire age keeps you safe on the highway. Rubber degrades over time due to UV exposure, heat cycles, and oxidation, even if the tread looks deep enough to pass inspection. On every Yokohama tire, a standardized Department of Transportation (DOT) code tells you the exact week and year it left the factory. Finding and decoding this string takes less than a minute once you know what to look for on the sidewall.
Finding the code requires inspecting both sides of the tire, though regulations mandate that the complete sequence appear on at least one outer sidewall. Look for the letters "DOT" stamped near the inner rim or close to the wheel well. Following those three letters, you'll see a series of numbers and letters, ending in a four-digit block that reveals the manufacture date.
Locate the DOT Serial Number on Your Yokohama Tire
The sequence you're hunting for is formally called the Tire Identification Number (TIN). It isn't always printed on both sides of the tire. If you scan the outer wall and see only the letters "DOT" without the rest of the serial numbers, turn your steering wheel all the way to one side or safely lift the vehicle to check the inner sidewall.
The code starts with a two- or three-character plant code identifying where the tire was built. For instance, a Yokohama tire manufactured at certain domestic or international plants will have specific facility characters assigned by the government. The characters immediately following the plant code represent the manufacturer's specific size and type codes. These middle characters help with inventory tracking and safety recalls, but they don't impact your day-to-day check for rubber age.
Decode the Four-Digit Manufacturing Date Stamp
The final four digits of the DOT sequence provide the vital information you need. These numbers stand completely on their own at the tail end of the serial string.
- The first two digits indicate the specific week of the year, running from 01 through 52.
- The last two digits represent the exact year of manufacture.
For example, if the stamp ends in 4518, the tire was built during the 45th week of 2018. If the numbers read 1223, it rolled out of the factory during the 12th week of 2023.
Older tires manufactured before the year 2000 used a three-digit code combined with a small triangle, but any modern Yokohama tire you purchase or inspect today will feature the standard four-digit format. If your tires show a three-digit code, they are decades old and must be replaced immediately regardless of tread depth. You can read more about standard vehicle safety guidelines through the National Highway Traffic Safety Administration.
Why Tire Age Matters More Than Tread Depth
Many drivers assume a tire is safe as long as the tread blocks measure above the legal minimum limit of 2/32 of an inch. Rubber is an organic compound that hardens and dries out as it ages. Plasticizers inside the rubber compound evaporate over the years, leading to microscopic dry rot cracks in the tread grooves and sidewalls.
Old, hardened rubber loses its grip on wet pavement, increasing stopping distances dramatically. Industry experts and manufacturers like Yokohama Tire generally recommend inspecting tires annually once they pass the five-year mark from their manufacturing date. Most tires reach the end of their operational lifespan between six and ten years, even if they've spent most of that time sitting unused as a spare.
Common Mistakes When Checking Tire Dates
People often misread or overlook critical details when checking tire stamps. Avoiding these errors saves you from driving on compromised rubber.
- Looking at the wrong numbers: Don't confuse the mold serial numbers, maximum pressure ratings, or part numbers with the DOT date stamp. The date code is always the final four digits of the sequence starting with "DOT".
- Checking only one tire: Tires get rotated, and sometimes a single punctured tire gets replaced long before the others. Check the date code on all four tires individually.
- Trusting the purchase date: Buying a brand-new tire from a shop doesn't mean it was manufactured yesterday. Tires stored in climate-controlled warehouses remain fine for a few years, but you should always verify the stamp before paying for a fresh installation.
Frequently Asked Questions
Can I drive on Yokohama tires that are over 6 years old?
You can drive on them if a professional inspection reveals no deep cracks, bulges, or loss of flexibility, but you should exercise caution. Rubber degrades differently depending on local climate, sun exposure, and storage conditions.
What should I do if the DOT code is missing on the outer sidewall?
Look at the inner sidewall facing the suspension components. Regulations require the full DOT stamp on at least one side of the tire, and manufacturers frequently place it on the inner side during specific production runs.
How do I check the date code on tires with white lettering?
On tires featuring raised white letters or specialized sidewall styling, the DOT string is often tucked into a smooth black band closer to the wheel rim. Run your fingers gently along the lower perimeter of the sidewall to find the stamped characters.
Are tires stored in a garage safe from aging?
Garaged vehicles experience less UV degradation, but oxidation still occurs continuously from ambient oxygen exposure. Even a spare tire kept safely in the trunk ages and loses its chemical resilience over time.
