How to check tread depth
- Wear bars: small raised bars across the bottom of the grooves. When the tread is level with them, the tire is at 2/32 inch and due for replacement.
- The penny test: put a penny into a groove with Lincoln’s head upside down. If you can see the top of his head, the tread is at or below about 2/32 inch.
- The quarter test: the same with a quarter and Washington’s head. If you can see the top of his head, you’re below about 4/32 inch — worth planning new tires, especially if you drive in rain or snow.
- A tread depth gauge is cheap and gives an exact reading.
Check several points across each tire. Wear on one edge often means an alignment or inflation problem.
How to read the tire date code
Every tire sold in the US has a DOT code on the sidewall. The last four digits are the week and year it was made: 2321 means the 23rd week of 2021. The code may only be printed on one side of the tire, so check the inside face if you can’t find it.
A tire can sit in a warehouse before it’s sold, so new tires aren’t always freshly made. It’s reasonable to check the date when you buy.
How many miles do tires last?
There’s no fixed number. Many all-season tires carry tread-life warranties in the tens of thousands of miles; performance and winter tires usually wear faster. Your driving, the roads, the load you carry and how well the tires are maintained all matter.
The biggest things you control: rotate on schedule, keep the pressures at the door-jamb figure, and have the alignment checked if the car pulls or wears tires unevenly.
Common questions
Can I replace just two tires?
Often, yes — and the usual advice is to put the newer pair on the rear axle for stability. On many all-wheel-drive vehicles, though, all four should match closely in tread depth; check your manual.
My tires have plenty of tread but are old. Are they safe?
Rubber hardens and can crack with age, even on a car that’s rarely driven. Have older tires inspected, and follow your vehicle and tire maker’s age guidance.
Does the spare count?
Yes — a spare ages too. Check its date code and pressure along with the others.