Roadside Safety Guides › Tire Tread

Tire Tread Safety: The Quarter Test

A 10-second check with a coin from your cup holder that can catch a bald tire before it fails.

How the Quarter Test Works

Take a quarter and insert it into your tire’s tread groove with Washington’s head pointing down, toward the tire. If the tread covers any part of his head, you’ve got more than 4/32″ of tread left — you’re fine. If you can see all of his head, your tread has worn down to 4/32″ or less, and it’s time to start planning for new tires. If you have a penny handy and Lincoln’s entire head is visible, that means you’re at 2/32″ — the legal minimum in most states, and genuinely unsafe, especially in wet or winter conditions.

Why This Test Actually Matters

Tread depth directly affects stopping distance and hydroplaning risk. A tire at 2/32″ can take significantly longer to stop on a wet road than a tire with healthy tread — the difference can be the length of a car or more at highway speeds. In Southwest Michigan, where lake-effect rain and snow are a near-constant seasonal factor, worn tread turns a routine commute into a real hazard.

Check All Four Tires, in Multiple Spots

Tires don’t always wear evenly. Check the inner edge, center, and outer edge of each tire — uneven wear across those three zones can indicate an alignment or suspension problem worth having looked at, separate from the tread depth itself. Front tires on front-wheel-drive vehicles (the majority of cars on the road) typically wear faster than rears.

What To Do If You Fail the Test

If Washington’s whole head shows on more than one tire, don’t wait for a blowout to force the issue — that’s exactly the scenario covered in our tire blowout guide. Get the tire(s) replaced before your next long drive or before winter weather arrives, whichever comes first.

How Often to Check

Once a month is a reasonable habit, and always before a long road trip. It takes less time than pumping gas. The NHTSA recommends checking tread depth and tire pressure together, since low pressure accelerates uneven wear.

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