How to Tell When Your Tires Need Replacing

Look at the tread first

Tread is what channels water away and grips the road. As it wears down, a tire does less of both.

Tires are built with treadwear indicators, small raised bars in the grooves. Federal rules require them, and they show when tread reaches one sixteenth of an inch. That equals 2/32 inch, or about 1.6 mm.

When the tread is level with the bars, Michelin says the tire has reached its minimum tread depth and should be replaced. USTMA says that at 2/32 inch it is time to visit a tire shop.

The penny test

You do not need a gauge to check. Place a penny in a tread groove with Lincoln's head facing down. If you can see the top of his head, the tread is at or below 2/32 inch.

Try several spots across the width of the tire. Uneven wear means the depth can differ from one edge to the other.

Wet roads need more than the minimum

Michelin notes that wet-road braking performance begins declining noticeably at 4/32 inch, when the tire's ability to channel water and resist hydroplaning is already reduced compared to new.

So 2/32 inch is a point where a tire is finished. It is not a point where the tire still performs like a new one.

Local rules differ. Some states set a legal minimum tread depth, and it is not always the same one. Check your state's rules or ask a tire shop.

Check the age of the tire

A tire can age out before the tread wears out. That is why tire makers give an age guide as well as a tread limit.

Michelin says tires should be inspected at least once a year by a trained tire professional after five years of service. It recommends replacing tires ten years after their date of manufacture, regardless of remaining tread depth or apparent condition.

A retailer, Discount Tire, says it recommends considering replacement at six years and will not service tires that are ten years or older.

Your vehicle's owner's manual may have its own guidance on tire age. Check it, and follow the shorter limit.

To find the age, read the last four digits of the DOT code. The first two give the week and the last two give the year. Our guide to the tire date code walks through it with examples.

Look for damage

Sidewall damage can be hard to see, so walk around the vehicle and check each tire. Michelin lists signs that call for replacement:

• Cuts, cracks, bulges or blisters on the sidewall
• Deep gashes that expose fabric cords
• Sidewall cracking that opens when flexed
• Damage from running the tire flat

If you see any of these, or you are unsure, ask a tire professional to inspect the tire.

Notice how the vehicle feels

Changes in how the vehicle drives can be a sign of tire trouble. Michelin points to unusual vibrations, pulling or changes in handling, which can suggest uneven wear or internal damage even when the tread looks acceptable.

It also lists reduced grip, longer braking distances or decreased traction, especially in wet conditions.

These symptoms can have other causes, such as alignment or suspension. A shop can tell you which is behind it.

Make it a monthly habit

USTMA suggests taking a few minutes each month to look over your tires. Watch for uneven wear, high and low areas, unusually smooth areas and other signs of damage.

Pressure belongs in the same check. USTMA says the recommended pressure is on a label on the driver's door or in the owner's manual.

Rotation helps tires wear evenly. USTMA says rotating tires based on the recommendations in your vehicle's owner's manual can prevent irregular tire wear. If no rotation period is specified, it recommends every 5,000 to 8,000 miles.

Alignment matters too. USTMA says misaligned wheels can lead to uneven, rapid tread wear and should be corrected by a tire dealer. It suggests having alignment checked at any indication of trouble, such as pulling.

A tire that wears unevenly may reach its limit on one edge long before the rest of the tread. That is why the penny test calls for several spots across the tire.

A quick checklist

Run through this list about once a month, and again before a long trip.

• Tread: do a penny test in several spots across each tire
• Wear bars: are any grooves level with the raised bars?
• Sidewalls: any cuts, cracks, bulges or blisters?
• Age: what does the date code say for each tire?
• Handling: any new vibration, pulling or longer stopping distances?
• Pressure: does it match the label on the driver's door?

If any answer worries you, take the vehicle to a tire shop and ask for an inspection. It is better to find a problem at the shop than on the road.

What to do next

If your tires need replacing, start by confirming the size. Read it from the tire sidewall or the driver's door placard. Our guide to reading a tire sidewall shows where to look.

Then use the tire finder to see tires and retailers for that size. If you want to compare your current size with another, the tire size calculator shows the difference in diameter and speedometer reading.

You do not always need a full set. Whether to replace two tires or four depends on your vehicle and on tread depth; see our guide on replacing two tires or four.

For a size such as 225/65R17 or 235/65R17, the size pages list the specifications and retailer links. They do not tell you whether a size suits your vehicle, so check your placard or ask a tire professional.