Most drivers only think about replacing their tires when the tread gets low. But age alone can make them dangerous. Even with plenty of tread, old tires can crack, separate, and blow out at high speeds. So, how old is too old? Here’s how to know exactly how old your tires are, and when to swap them before they fail.

At what point should tires be replaced?

Tires should be replaced when the tread wears below 2/32 of an inch or when they show signs of aging. Even if they have tread left, cracks, bulges, or separation mean it’s time for a new set.

Tread depth affects grip, especially in wet weather. AAA research found that worn tires increase stopping distances by 43% at highway speeds. Use the “quarter test” to check yours: Stick a quarter into your tire tread. If you see the top of George Washington’s head, your tread is too low. But tread depth isn’t the only issue—tire age matters too.

Sunlight, heat, and time break down rubber. Even with deep tread, old tires can crack and separate. Once your tires reach five or six years old, start inspecting them closely. If they’re 10 years old, most shops won’t even mount them.

Are 7-year-old tires still good?

Seven-year-old tires might still be safe, but they need a close inspection for cracks or hardening. Most experts say six years is the limit for reliable performance.

Edmunds warns that even tires with good tread can be dangerous if they’re too old. In extreme cases, old tires have caused fatal accidents, including the crash that killed actor Paul Walker. His Porsche had 9-year-old tires.

To check your tires’ age, look for the four-digit DOT code on the sidewall. The first two numbers are the week they were made, the last two are the year. If yours are more than six years old, it’s time to think about replacement—especially if they’ve been exposed to heat, UV rays, or improper storage.

The truth about tires

Your tires might still look fine, but age alone can make them unsafe. Cracking, stiffening, and tread separation can lead to dangerous blowouts. Most experts, including AAA and tire manufacturers, agree: Six years is the limit for reliable performance. If your tires are older, check their date codes and replace them before they become a hazard.