How to check your tires: pressure, tread, damage and repairs
Set the right pressure, read tread wear and know which tire repairs are safe
Your tires are the only part of your car that touches the road. Every stop, turn and swerve depends on four patches of rubber, each about the size of your hand. When those patches are underinflated, worn or damaged, the best brakes and safety systems in the world cannot make up for it.
Tire problems are not rare. In 2024, 511 people died in tire related crashes in the United States [1]. A NHTSA study looked at crashes from 2005 through 2007. When a tire was 25 percent or more underinflated, tire problems were about three times as likely to come right before the crash [2]. Yet NHTSA says only 19 percent of drivers keep their tires properly inflated [1].
The good news is that tire care is the easiest safety job on any car. This guide covers what to check, how to read what you find, and what to ask for at the tire shop.
Pressure: the most important number
Why pressure matters
An underinflated tire flexes more as it rolls. That builds heat, wears the tire faster and makes steering and braking less precise. NHTSA says proper inflation can extend tire life by an average of 4,700 miles and save up to 11 cents per gallon of fuel [1].
Too much air is a problem too. An overinflated tire has a smaller patch touching the road, which can reduce grip and cause the center of the tread to wear out early.
Where to find the right number
The correct pressure is on the tire and loading label, usually on the driver’s door frame. It is also in your owner’s manual [1]. The front and rear tires may need different pressures.
The number molded on the tire’s sidewall is the most air the tire can safely hold. It is not the right pressure for your car [1].
How to check, step by step
- Check when the tires are cold. NHTSA says that means the car has not been driven for at least three hours [1].
- Remove the valve cap from the first tire.
- Press the gauge firmly onto the valve stem until the hissing stops.
- Read the gauge and compare it with the door label.
- Add air in short bursts, then check again. If you overfill, press the small pin in the valve to let some out.
- Replace the cap and move to the next tire.
- Check the spare, if you have one. Compact spares often need a higher pressure than regular tires [3].
Pencil, dial and digital gauges all work. Pick one you find easy to read and keep it in the glove box, so you do not have to rely on the gauge at an air pump.
If you must check warm tires, such as at a gas station, add air if they are low. Do not let air out to match the label. NHTSA advises rechecking when the tires are cold [1].
Cold weather and pressure
Tire pressure drops as the temperature falls. NHTSA’s winter checklist reminds drivers to check pressure often in cold weather [4]. That is why the tire light often comes on during the first cold morning of fall.
The tire pressure warning light
Cars built for the 2008 model year and later have a tire pressure monitoring system [1]. It is a helpful backstop, but it is not a replacement for a gauge.
The federal rule requires the warning to come on when a tire is 25 percent or more below the recommended pressure [5]. On a tire that should be at 35 psi, that means the light may stay off until the tire is down to about 26 psi.
Comparison compiled by Safety Behind the Wheel Foundation
What the tire pressure light is telling you
| What you see | What it means | What to do |
|---|---|---|
| Light comes on and stays on | At least one tire is significantly underinflated | Check all tires with a gauge and fill them soon |
| Light comes on during a cold morning, then goes off | Pressure is borderline and rose as the tires warmed | Check and fill when the tires are cold |
| Light flashes for 60 to 90 seconds, then stays on | The monitoring system has a problem and may not warn you | Have the system inspected |
Source: Based on NHTSA tire guidance [1].
After new tires, a rotation or a flat repair, check your owner’s manual. Some systems need to be reset or relearn which sensor is on which wheel.
Tread: how much is enough
The penny and quarter tests
The legal minimum in many states is 2/32 inch. NHTSA’s penny test checks that level. Put a penny upside down in a groove. If you can see the top of Lincoln’s head, the tire needs to be replaced [1].
That standard is too low for wet roads. AAA recommends replacing tires at 4/32 inch [6]. To check, put a quarter upside down in a groove. If you can see all of Washington’s head, start shopping for tires [6].
Check several grooves across each tire, and in a few places around it. Tires often wear unevenly.
Why 4/32 inch matters in the rain
Tread grooves channel water out from under the tire. As the grooves get shallow, the tire can ride up on a film of water. AAA tested tires worn to 4/32 inch on wet pavement at highway speed. Stopping distances grew by an average of 43 percent, or 87 feet, for passenger cars [6]. When cars on new tires had stopped from 60 mph, cars on the worn tires were still going about 40 mph [6].
Crash data tells the same story. In NHTSA’s study, 26 percent of vehicles with tread of 2/32 inch or less had a tire problem right before the crash. For tires with 3/32 to 4/32 inch, it was 8 percent [2].
Wear bars
Tires have raised bars molded across the bottom of the grooves. When the tread wears down level with them, the tire is at 2/32 inch and is done [1].
Read the wear pattern
How a tire wears is a clue to what is wrong with the car. A tire shop can confirm the cause.
Comparison compiled by Safety Behind the Wheel Foundation
Tire wear patterns and likely causes
| Pattern | Likely cause | What to do |
|---|---|---|
| Both outer edges worn | Low pressure | Check pressure monthly and keep it at the label number |
| Center worn more than the edges | Too much pressure | Set pressure to the label number, checked cold |
| One edge worn | Wheel alignment problem | Have the alignment checked |
| Scalloped or cupped patches | Worn shocks or struts, or wheels out of balance | Have the suspension and balance checked |
| Car pulls to one side | Low pressure on one side or a front end problem | Check pressure, then have the alignment checked |
Source: Based on Federal Trade Commission auto repair guidance [7] and NHTSA tire guidance [1].
Look for damage
Once a month, and after hitting a pothole or curb hard, look closely at each tire. Turn the steering wheel all the way to one side to see more of the front tires.
Look for:
- Bulges or bubbles on the sidewall. These mean the inside of the tire is damaged.
- Cuts, cracks or chunks missing from the tread or sidewall.
- Exposed cords or steel belts showing through the rubber.
- Nails, screws or stones stuck in the tread.
- Fine cracks in the rubber, a sign of aging. See our guide on tire age.
NHTSA says to replace tires showing signs of damage, irregular wear, underinflation or overloading [1].
If you find a nail
Do not pull it out. The nail may be partly sealing the hole. Check the pressure, and if the tire is holding air, drive gently to a tire shop for an inspection. If it is losing air quickly, use the spare.
Flat repairs: which ones are safe
Not every flat can be fixed, and not every fix is safe. The U.S. Tire Manufacturers Association sets out the standards for a proper repair [8]:
- Tread area only. Repairs are limited to the tread. Damage in the shoulder or sidewall cannot be repaired.
- Small holes only. The puncture cannot be larger than 1/4 inch across.
- A plug and a patch together. A plug alone is not an acceptable repair. The plug fills the hole and the patch seals the inside.
- From the inside. The tire must be taken off the wheel so the inside can be inspected and repaired.
- No overlapping repairs. Two repairs too close together means a new tire.
Run flat tires and some other tires may have extra repair limits from their maker [8]. Ask the shop to show you where the puncture is before you approve the repair.
Sealant kits are temporary
Many newer cars carry a sealant kit instead of a spare. These kits are meant to get you to a shop. One Honda manual says to use its kit only for small punctures in the tread, not for damage larger than 5/32 inch or any sidewall damage. After using it, drive no faster than 50 mph and get a lasting repair [9]. Tell the tire shop you used sealant.
Rotation, balance and alignment
Rotation. If your vehicle maker recommends it, NHTSA says to rotate tires every 5,000 to 8,000 miles, or sooner if you see uneven wear [1]. Some vehicles have different sizes front and rear and cannot be rotated the usual way.
Balance. Balancing keeps wheels from shaking. New tires should always be balanced when installed [1]. A vibration in the steering wheel at highway speed is a common sign a wheel is out of balance.
Alignment. A wheel alignment keeps the car tracking straight and helps tires last [1]. Have it checked if the car pulls, the steering wheel is off center, or after a hard hit to a curb.
Buying new tires
Match what your car needs
NHTSA says to buy tires the same size as your original tires, or another size your vehicle maker recommends [1]. The size is on the door label and in the manual. Ask the shop to confirm that the new tires’ load and speed ratings meet or beat the originals.
Read the quality grades
Most passenger tires carry three grades on the sidewall, set by federal rules.
Comparison compiled by Safety Behind the Wheel Foundation
Tire quality grades
| Grade | What it measures | How to read it |
|---|---|---|
| Treadwear | How long the tread should last in a standard test | A higher number should wear more slowly |
| Traction | Ability to stop on wet pavement | AA is best, then A, B and C |
| Temperature | Resistance to heat buildup | A is best, then B and C |
Source: Based on NHTSA tire guidance [1].
For wet weather safety, the traction grade matters most. NHTSA reports that 77 percent of tire lines are rated A and 15 percent are rated AA [1].
Replacing two instead of four
Replacing all four at once keeps grip even. If you replace only two, Michelin generally recommends putting the new tires on the rear axle [10]. Deeper tread in back helps the car stay stable on wet roads and resist spinning out. Match the size and type of your other tires [10].
Check the date and register your tires
Look at the last four digits of the DOT code on the sidewall. They show the week and year the tire was made [1]. Avoid tires that have sat in storage for years.
Then register the tires with the maker. Registration is how the maker reaches you if your tires are recalled. The National Transportation Safety Board found in 2015 that only about 10 percent of tires sold through independent dealers were registered [11]. Ask the shop to register them, or do it yourself on the maker’s website. You can also look up tire recalls on NHTSA’s site [1].
Know your spare
Find out what your car carries before you need it.
- Full size spare. It can replace a regular tire. Check its pressure monthly and its age.
- Compact spare. A small spare for short emergency trips. A common limit is 50 mph. Check the sidewall for the exact speed and distance limits [3].
- Sealant kit. A can of sealant and a small pump, for small tread punctures only [9].
- Run flat tires. Tires built to keep going for a limited distance after losing air. Follow your manual’s speed and distance limits.
NHTSA says not to use a spare as a replacement for worn tires, except in an emergency [1].
Your tire checklist
Frequently asked questions
How often should I check tire pressure?
At least once a month and before long trips, including the spare [1]. Check more often when the weather turns cold.
Can I just use a plug kit on my own tire?
A plug alone does not meet the tire industry’s repair standard. A proper repair needs a plug and a patch installed from inside the tire [8]. Use a plug or sealant only to get to a shop.
My tire pressure light came on, but the tires look fine. What should I do?
Check all four with a gauge. A tire can be 25 percent low and still look normal. If they are all at the right pressure and the light stays on, have the system checked.
Should I buy the cheapest tires?
Price matters, but compare the traction grade and reviews too. A tire rated AA or A for traction stops better on wet pavement in standard tests [1].
Related articles
- Vehicle maintenance for safety: tires, brakes, lights and warning signs
- How to use a tire pressure gauge: cold readings, the right number and a lasting routine
- Tire age and the DOT code: how to tell when tires are too old
- Choosing replacement tires: how to match size, load, speed rating, age and type
- Emergency tire repair kits: which flats they fix and what to tell the tire shop
- Seasonal car care: getting ready for winter, summer, rain and road trips
Sources and further reading
- 1NHTSA. Tires. nhtsa.gov/vehicle-safety/tires
- 2Automotive Fleet. NHTSA Report Says Low Tire Tread Depth and Underinflation Increase Collision Chances. May 10, 2012. automotive-fleet.com/…/nhtsa-report-says-low-tire-tread
- 3Michelin. Driving on a Spare Tire. michelinman.com/…/driving-on-a-spare-tire
- 4NHTSA. Winter Weather Driving Tips 2023 to 2024. nhtsa.gov/…/Winter-Weather-Driving-Tips-2023
- 5Federal Register. Federal Motor Vehicle Safety Standards; Tire Pressure Monitoring Systems final rule (FMVSS 138). April 8, 2005. govinfo.gov/…/05-6741.pdf
- 6AAA Newsroom. Tread Lightly: Worn Tires Put Drivers at Risk. June 7, 2018. newsroom.aaa.com/…/tread-lightly-worn-tires-drivers
- 7Federal Trade Commission. Auto Repair Basics. consumer.ftc.gov/…/0211-auto-repair-basics
- 8U.S. Tire Manufacturers Association. Tire Repair Basics. ustires.org/…/tire-repair-basics
- 9Honda owner’s manual. Models with temporary tire repair kit. techinfo.honda.com/…/131271047-15363.html
- 10Michelin. Guidance on mixing tires and replacing two tires. michelinman.com/mixingTires.html
- 11Safety+Health magazine. Flaws in tire registration, recalls can lead to crashes, NTSB says. November 3, 2015. safetyandhealthmagazine.com/…/13250-flaws-in-tire-registration
This article reflects the safety priorities of tire safety and crash prevention. It is general education, not mechanical advice. Follow your owner’s manual and the tire maker’s guidance, and have a tire professional inspect damaged tires. Reviewed November 2026.
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