The last four digits of a tire's full DOT Tire Identification Number show its manufacturing week and year. A code ending in 3520 means the tire was made in week 35 of 2020. That date is an important inspection trigger, but it is not a universal expiration date: damage, low tread, chronic underinflation or a vehicle-maker limit can require replacement sooner.

For a U.S. driver, the sound decision rule is to follow the vehicle and tire manufacturers' instructions, inspect older tires professionally, and never let acceptable-looking tread overrule cracks, bulges, exposed cords or a ten-year manufacturer limit. NHTSA says some vehicle and tire makers recommend replacement at six to ten years regardless of treadwear.

Where to find the tire's date

Look for the letters DOT on the sidewall, followed by the Tire Identification Number, or TIN. On tires made since 2000, the final four digits of the complete TIN are the date code:

  • the first two digits are the production week, from 01 through 52 or 53;
  • the final two digits are the year;
  • 1424, for example, means week 14 of 2024.

NHTSA warns that the complete TIN may appear on only one side of the tire. If the visible sidewall does not end in four date digits, check the inward-facing side safely at a tire shop; do not crawl under a vehicle supported only by a jack.

Read all four road tires and the spare. A replacement tire may be older or newer than the others, and the spare can be the oldest tire on the vehicle because its tread is rarely used.

Does the DOT date create a legal expiration date?

No single federal rule says that every passenger-car tire expires at one fixed age. The U.S. Tire Manufacturers Association says service life cannot be predicted from calendar age alone because heat, storage, inflation, loads, speed and impacts vary. It advises drivers to follow any service-life recommendation issued by the vehicle or tire maker and to use periodic professional inspections.

That is not permission to ignore age. NHTSA states that aging tires are more prone to failure and notes that some makers specify replacement between six and ten years. Michelin's published U.S. guidance calls for close professional inspection after five years of use and replacement by ten years from manufacture, including the spare, regardless of remaining tread.

The applicable limit is the most specific documented instruction for the tires and vehicle in front of you. Check the owner's manual, the tire maker's current care guide and any warranty conditions. A ten-year ceiling from one brand should not be copied automatically to a different tire whose maker or vehicle manufacturer sets an earlier limit.

Age is not the only replacement trigger

A two-year-old tire can be unfit after a pothole impact, prolonged underinflation or sidewall damage. A seven-year-old tire may still have deep tread yet need closer inspection because deterioration can be internal or difficult to see.

Replace or remove a tire from service when a qualified technician finds conditions such as:

  • a bulge, bubble, exposed cord, deep cut or sidewall cracking;
  • tread worn to the molded wear bars or the applicable state minimum;
  • a puncture in a non-repairable shoulder or sidewall area;
  • vibration, repeated pressure loss or irregular wear that remains unexplained;
  • age at or beyond the documented manufacturer limit.

The pressure printed on the sidewall is a maximum tire rating, not automatically the correct pressure for the car. Use the cold-pressure value on the driver's-door placard or in the owner's manual. NHTSA recommends checking pressure monthly, including the spare.

Why the spare needs a separate decision

NHTSA specifically warns that full-size spares age even when their tread looks unused. It recommends that a full-size spare not become a routine replacement for worn road tires; it is for an emergency such as a flat. Compact temporary spares also have their own pressure, speed and distance instructions, normally printed on the tire and described in the owner's manual.

At the next tire service, ask the shop to record the spare's DOT date and pressure. If the spare is beyond its maker's age limit, replacing it before a road trip is more useful than discovering the problem on the shoulder.

What to check when buying tires or a used car

For new replacement tires, read the DOT date before installation and ask why an unusually old tire is being sold. Age alone does not prove improper storage, but it reduces the time remaining before an age-based manufacturer limit.

On a used car, compare all five dates where a spare exists. Mixed dates can reveal normal replacement, but they should prompt questions about accident damage, uneven wear or an all-wheel-drive system that may require closely matched rolling circumference. Our summer-versus-all-season tire comparison explains why tread type and local conditions still matter after the age check.

The practical rule is simple: decode the TIN, inspect the whole tire, and apply the vehicle and tire maker's written limit. Replace immediately for structural damage or unsafe tread; schedule professional inspections as the tires age; and do not treat a clean sidewall or unused spare as proof of safety.