How to read tire date codes

Where to find the date code

The date code is the last part of the DOT number molded into the tire sidewall. It sits near the wheel and may appear on only one side, inner or outer, depending on the maker.

How to read it

• Tires made in 2000 or later end in four digits
• The first two digits are the week of the year the tire was made
• The last two digits are the year
• Example: 2118 means the 21st week of 2018
• Tires made before 2000 use a three-digit code, so a very old tire is easy to spot

Why tire age matters

Tires are made of rubber compounds that break down over time through exposure to oxygen, sunlight, heat and weather, even when the tread looks fine. Older tires can lose flexibility and grip.

The U.S. government's safercar.gov notes that high ambient temperatures can speed up tire aging, which can contribute to failures including tread separation.

How old is too old?

There is no single rule. Some vehicle and tire makers advise replacing tires at about six years, and Michelin recommends replacing tires at ten years from the date of manufacture, spares included, even if they look usable. Many guides suggest having tires inspected every year once they reach five years old. Check your vehicle owner's manual and your tire maker's guidance.

Signs of aging and dry rot

If you see these signs, have the tire inspected before you drive on it.

• Cracks in the sidewall or between tread blocks, looking like cracked leather
• Pitting, splintering or a faded, lighter colour
• Rubber that feels brittle or rigid
• Steering or whole-vehicle wobble in severe cases, which can mean the tread is separating

What causes dry rot

Heat, sunlight and age all play a part. The most common and avoidable cause is long periods of sitting still. Tires are designed to be used, and a vehicle parked for months outdoors in changing temperatures is more likely to see cracking.

Tires you rarely use and spares

Normal wear usually retires a tire before age does. The exceptions are occasionally driven cars and spares, which are often never replaced. Check a spare at least once a year, especially one mounted outside the vehicle.

For storage, keep tires indoors, out of direct sunlight, away from ozone sources and extreme temperature swings. If possible, take them off the vehicle before long-term storage.

Buying new tires

Check the date code on any new tires you are given, and ask us for the manufacture date if you want it confirmed before you order.