Tire Replacement Guidelines: What the Experts Recommend

Tread depth standards

The most common reason tires are replaced is worn tread. Federal standards for new tires require treadwear indicators, which are projections in the main grooves that become visible when the tire is close to the end of its useful life. For example, Standard No. 129 for non-pneumatic spare tires specifies that the indicator must appear when tread depth is 1/16 inch. While you may not rely on a penny test, you can simply look for these indicators in the grooves.

As a rule of thumb, when the tread is level with the wear bars, the tire is legally worn out and should be replaced. The indicator depth is a good point to start shopping for a new set. Many states require replacement at 2/32 inch, but the federal standard ensures that the indicator gives you a clear visual cue. For light truck tires that come with deep tread (18/32 inch or more), Standard No. 119 treats them separately, so they may have different wear limits.

• Check the built-in tread wear indicators in the main grooves.
• If you see the indicators flush with the outer tread, the tire is at 1/16 inch and needs replacement.
• For light truck tires, note that deep-tread versions (18/32 inch or more) have a different baseline.

Age and the DOT code

Tread depth is not the only factor. Rubber degrades over time, even if the tire is not used. The Department of Transportation requires each tire to have a DOT symbol and an identification code that includes the week and year of manufacture. You can find this information on the sidewall, and it tells you how old the tire really is.

Industry experts often recommend replacing tires after about ten years, regardless of tread depth, but the exact number depends on climate, storage, and usage. If your tires have been in use for many years, it is wise to have them inspected by a professional. The DOT date code is the starting point for this evaluation.

Heat and sunlight accelerate rubber aging, so tires stored in a garage in a hot climate may need replacement sooner. Always check the date code even on used or spare tires, because an old spare that has never been mounted can still be unsafe.

When damage means new tires

Any visible damage to the tire structure is a reason to replace it. Federal standards define conditions such as bead separation, tread separation, sidewall cracking, chunking, and open splices. If you see any of these, the tire is no longer safe. The definitions in Standard No. 109 describe these failure modes, and they apply to any tire.

Also look for cuts, bulges, or punctures that cannot be properly repaired. A tire with a bulge in the sidewall should be replaced immediately, as it indicates internal damage. Similarly, if the tread is showing cords, that is a structural failure. Learn more about tire tread wear causes to identify damage early.

Small punctures in the tread area can sometimes be repaired, but repairs are not permitted if the damage is in the sidewall or if the puncture is too large. The Tire Industry Association offers training on proper repair procedures, but professional inspection is your best bet.

• Bead or sidewall separation: replace immediately.
• Cracks extending to the cords: unsafe, replace.
• Chunking (pieces missing): a sign of severe wear, replace.
• Bulges or blisters: internal breakage, do not drive on them.

Reading wear patterns

Uneven tread wear can point to mechanical problems. For example, under-inflation causes the shoulders to wear faster, while over-inflation wears the center. The Department of Energy advises that keeping tires properly inflated can improve fuel economy by 0.6% on average, and under-inflated tires also wear unevenly. Regular pressure checks and tire rotations help extend tread life.

If you notice one tire wearing more than others, it could indicate an alignment issue or a problem with the suspension. Replacing a set of tires before the pattern becomes severe can often correct the problem, but if the wear is extreme, you may need to replace the affected tires and address the underlying cause. See our guide on tire rotation patterns for maintenance tips.

Spare tires and temporary use

Spare tires, whether T-type temporary spares or non-pneumatic spares, have their own rules. Standard No. 129 applies to new non-pneumatic spare tires and requires tread wear indicators at 1/16 inch, just like full-size tires. T-type temporary spares are designed for limited speed and distance, typically not exceeding 50 mph, and should be replaced if they show any damage or age.

Never use a temporary spare as a permanent replacement. If you must drive on a spare, check its pressure before mounting, because it may have been sitting for years. If the spare is old, it may be safer to replace it with a full-size tire. For guidance on selecting a new set, our best car and SUV tires guide is a good start.

Your replacement checklist

Use these guidelines to decide when to buy new tires: check the tread wear indicators, confirm the age with the DOT code, inspect for damage, and monitor wear patterns. If any of these point to a problem, it is time to start comparing replacement options.

For a new set, consider your driving needs and climate. If you drive a car or SUV, our best car and SUV tires guide lists top picks by spec. In snowy regions, a dedicated winter tire may be worth the investment. For year-round use, all-season tires balance performance and convenience.

What to pick for your use

Questions

What is the legal minimum tread depth?

Federal standards require treadwear indicators that become visible at 1/16 inch, which is effectively 2/32 inch. Most jurisdictions consider that the legal minimum, but it is safer to replace before reaching that point.

How can I tell how old my tires are?

Look for the DOT code on the sidewall. The last four digits indicate the week and year of manufacture (e.g., 3223 means the 32nd week of 2023). This is required by federal regulation.

Can I replace just one tire?

It is best to replace tires in pairs or sets to maintain consistent handling and traction. If the other tires are worn significantly, matching tread depth is important. Always check with a professional.

What should I do if I see a bulge on my tire?

A bulge indicates internal damage and can lead to a blowout. Replace the tire immediately and do not drive on it at highway speeds.

Do winter tires need to be replaced before winter?

Yes. Winter tires lose effectiveness as tread wears below 6/32 inch, but many experts suggest replacing them when they reach 4/32 inch. Check the tread depth and the age before the season starts.

Is it safe to use an old spare tire?

Spare tires age just like any other tire. Check the DOT date code and the tire's condition. If it is over ten years old or shows cracks, replace it with a full-size tire or a new spare.