Finding the exact birth date of your Yokohama tires requires locating the Department of Transportation identification sequence stamped directly onto the outer sidewall. Every modern tire sold features a four-digit stamp where the first pair of numbers signifies the production week and the second pair represents the manufacturing year. If your tire reads 2423, it rolled out of the factory during the 24th week of 2023, which is roughly mid-June.
Knowing this date matters because rubber compounds degrade over time due to heat, UV exposure, and environmental oxidation, regardless of tread depth. When you buy used vehicles, store spare tires, or inspect a set that has sat in a garage for years, checking the age code prevents unexpected tread separation or blowouts on the highway.
Locating the DOT Code on Yokohama Sidewalls
Finding the code starts with a visual sweep around the outer perimeter of the tire wheel rim. Look for the letters "DOT" molded in raised lettering near the bead where the tire meets the wheel.
Sometimes, vehicle manufacturers mount tires with the full sequence facing inward toward the chassis suspension components. If you don't see the code on the outside face, you'll need to crawl underneath or jack up the vehicle to inspect the inner sidewall.
The full string consists of a combination of letters and numbers up to 13 characters long. For example, a typical Yokohama marking looks like FDAPLJO4518. You don't need to worry about the plant code or size identifier characters for determining age; your target is always the final block of numbers at the very end of that string.
Breaking Down the Four-Digit Date Code
Once you locate the final four digits, reading them is straightforward. The coding standard has been universal since the year 2000, governed by federal regulations for all tires sold in North America.
- The first two digits show the exact calendar week of manufacture, ranging from 01 through 52.
- The final two digits represent the production year, such as 18 for 2018 or 24 for 2024.
For instance, a stamp ending in 1024 means the tire was produced during the 10th week of 2024. If you spot a three-digit code instead, such as 459, you are looking at an older tire manufactured in the 45th week of 1999 (or 1989), which should be replaced immediately due to severe rubber degradation. You can cross-reference manufacturer safety guidelines directly on the National Highway Traffic Safety Administration portal.
How Tire Age Affects Performance and Safety
Rubber isn't inert; it hardens as volatile oils evaporate over the years. Even if a Yokohama tire has deep tread remaining, internal steel belts and sidewall plies weaken after years of thermal cycling.
Most major automakers and tire manufacturers, including guidance provided by Yokohama Tire Corporation, recommend a thorough professional inspection once a tire reaches five years of service. Tires that pass the five-year mark should generally be retired completely once they hit ten years from their manufacture date, even if they were never mounted on a vehicle.
Dry rot manifests as tiny hairline cracks running along the tread grooves or the outer sidewall. If you spot these fissures alongside an old date code, don't risk driving on them at highway speeds.
Common Mistakes When Reading Tire Codes
People often misread the manufacturing date by confusing random serial numbers or mold batch codes with the actual DOT date stamp. Always look for the specific four-digit box or standalone set near the end of the DOT sequence.
Another frequent error involves checking only one tire and assuming the rest match. Vehicles often receive replacement tires individually or in pairs after a flat, meaning your front tires might be two years newer than your rear tires. Check all four positions, including the trunk spare, because a spare stored in a hot trunk degrades faster than tires exposed to ambient outdoor air while rolling.
Frequently Asked Questions
What should I do if my Yokohama tires are over six years old?
Take your vehicle to a certified alignment and tire shop for a professional inspection. They will check for internal separation, bead damage, and deep sidewall cracking that you might miss during a casual driveway check.
Does the mileage warranty cover old tires?
Tire warranties generally cover defects in materials and workmanship for a specific period or tread wear limit, but they do not cover natural aging or environmental degradation past the manufacturer's recommended lifespan.
Are tires manufactured overseas aged differently?
No, the Department of Transportation standard applies to all tires imported into North America, meaning Yokohama plants in Japan, the Philippines, or the United States all use the exact same four-digit week-and-year format.
Can I spray anything on my tires to prevent cracking?
Using harsh petroleum-based dressings can actually strip natural anti-ozonants out of the rubber compound, accelerating dry rot. Stick to mild soap and water for routine cleaning.
