Tires degrade from the inside out — the rubber oxidizes and hardens over time, regardless of how much tread remains. A 10-year-old tire with 6/32" of tread left is not safe to drive on. Here is how to find and read the date code, and what the numbers mean for replacement.
Finding the DOT date code
The DOT code is molded into the sidewall of every tire — usually on the inward-facing side of the tire (requires looking underneath or removing the wheel for full visibility on some vehicles).
The full DOT code looks like: DOT U2LL LMLR 5118. The last four digits are the date code.
The date code is four digits: the first two are the week of manufacture, the last two are the year. 5118 means week 51 of 2018.
Before 2000, tires used a three-digit code with the week and a single-digit year. Any tire with a three-digit date code is over 25 years old and should be replaced regardless of condition.
How old is too old?
Most tire manufacturers recommend replacing tires at 6 years from the manufacture date regardless of tread depth. At 10 years: mandatory replacement regardless of appearance.
The logic: tire rubber contains antioxidants and antiozonants that slow degradation — but they deplete over time. By year 6, significant oxidation has typically occurred in the inner liner and carcass even if the outer tread looks serviceable.
Vehicle manufacturers (including Ford, Chrysler, and Toyota) specify 6-year retirement. Tire manufacturer policies vary: Michelin and Continental say 10 years max with inspections after year 5; Bridgestone and Firestone say 10 years.
Practical recommendation: replace tires older than 6 years if they see regular highway driving. Replace at 10 years regardless.
Signs of age-related degradation
Surface cracking or crazing: small cracks in the tread grooves or sidewall. Fine surface cracks are cosmetic; cracks extending deeper than 1mm indicate significant rubber degradation.
Sidewall cracking: cracks along the sidewall face or near the bead area. Any sidewall cracking that reaches the cord layer requires immediate replacement.
Dry rot: visible fading, discoloration, and texture change from oxidation. Tires affected by dry rot can fail without warning.
Stiffness: aged tires often feel hard and inflexible compared to new tires — grip is compromised even with adequate tread depth.
Frequently asked
My used car has tires with good tread but a 2016 date code. Should I replace them?
Yes. Tires from 2016 are over 8 years old and past the 6-year recommended service life. The tread depth looks fine but the rubber chemistry has significantly degraded. Budget for replacement soon — this is a safety issue, not a cosmetic one.
Do spare tires have date codes?
Yes — and spare tires (especially compact spares stored under vehicles) are frequently neglected. Check the date code on your spare. A 10-year-old compact spare should be replaced even if it was never used. The spare is not visible during normal inspection, making age-related degradation easy to miss.
Can I buy old new-old-stock (NOS) tires?
Avoid it. Some retailers sell tires that are technically new (unused, full tread) but 3-5 years old. The purchase date is irrelevant — the manufacture date determines tire age. Check the DOT code before any tire purchase. A tire sold as new in 2024 with a manufacture date of 2019 has 5 years of aging before you even mount it.
Keep reading
Last updated 2026-06-27. General guidance only — confirm specifics with a local shop for your exact vehicle.