How to check tire tread depth

Tread channels water away from under the tire. As it wears down, the car takes longer to stop and slides more easily in the wet.

The legal minimum

In the US most states set the minimum at 2/32 of an inch, and in the UK and most of Europe it is 1.6 mm. That is the point at which tires are legally worn out, and many experts advise replacing them sooner.

When to replace

Stopping distances in the wet get noticeably longer as tread falls below about 4/32 of an inch (3 mm). It is sensible to start shopping for new tires at that point.

The coin test

Push a US penny into a tread groove with Abraham Lincoln’s head upside down and facing you.
If you can see all of his head, the tread is at or below 2/32 of an inch and the tire is worn out.
In the UK, a 20p coin works the same way: if you can see the outer rim, the tread may be below the legal limit.
Check several places across each tire, not just one.

Look for more than depth

Check for cracks, bulges and nails too. Tires also age: rubber hardens after about 6 to 10 years even if the tread looks fine. The date is the four-digit code on the sidewall: week then year.

Common questions

Should I replace all four tires at once?

Not always, but at least both on the same axle. Replace in pairs or sets and put the newest tires on the rear for stability. Ask your tire shop.

What is uneven wear?

When one edge or the middle wears faster than the rest. It points to wrong tire pressure or a wheel alignment problem.

General guidance, not professional advice. Intervals are typical ranges and vary by car, so check your owner’s manual and ask a qualified mechanic if you’re unsure.