Car tires endure significant wear and tear, requiring replacement when the tread depth falls below a safe level. However, road hazards like potholes, rocks and debris can also damage tires, potentially requiring replacement on an earlier schedule.
Knowing when to replace tires is crucial for safety, overall car performance and cost savings, but many drivers might not know when it's time to swap tires in for a new set. Whether you're a newly licensed driver or someone with years of experience, everyone should know when to replace tires based on tread depth and other potential hazards.
Having a car maintenance checklist on hand can help keep track of this activity and more. Keep reading to learn about common signs of when to replace your tires and common signs to look out for.
How to Measure Tire Tread Depth
Adequate tire tread depth is necessary to maintain traction and shed water on wet, slippery roads. Knowing how to measure tread depth will help you know when to replace a tire and if it's safe to drive on. You can measure tread depth with an inexpensive gauge available at any auto parts store for an accurate measurement, or you can use the traditional quarter and penny tests to get a close estimate.
For reference, a good tire tread depth is 6/32 or deeper, while 4/32 to 5/32 is acceptable but indicates that you should replace your tires soon. Tread depths of 2/32 or lower should be replaced immediately due to safety (and legal) concerns.
Insert a quarter into a tread groove with the top of Washington's head facing down. If the top of his head is not visible, your tires have at least 4/32 of tread and are fine for continued use. If you can see above the top of Washington's head, it is time to start shopping for new tires. Take multiple measurements across the tread to help ensure accurate results.
You perform a penny test the same way, except that if you can see above the top of Lincoln's head, your tires have less than 2/32 of tread. This is below the legal minimum in most states and requires immediate tire replacement. Tires worn to this level will also have visible wear indicators (thin bald strips) running from side to side across two or more tread segments.
AAA recommends the quarter test over the penny test since tires that fail the penny test are already considered unsafe. The quarter test better indicates when tires are starting to lose effectiveness. For best results, use a tire depth gauge to know exactly how safe your tires are and remember to schedule regular tire inspections at least once a year.
Why Your Tire Tread Depth Is Important
You might not think about it often, but understanding your tire tread depth is just as important as knowing about any other car maintenance. Tire tread impacts car performance and safety, especially when driving on wet roads.
Other reasons that tire tread depth is essential include:
- Stopping distance: Tires with decreased tread depth take longer to stop, increasing the risk of an accident. An ideal tread depth allows you to stop your car faster, helping to avoid accidents or other hazards.
- Tire grip: The job of the tire's grooves is to grip the road to help the car brake, turn and accelerate. As the tread depth decreases, it becomes harder for the tire to grip the road. The same is true for driving in ice and snow , the grooves help the tires with traction to minimize slipping.
- Legalities: In most places, the legal minimum tread depth is 2/32". If your tire tread depth is less than that, you could be fined due to unsafe driving.
- Car handling: Adequate tread depth helps your car stably navigate corners and curves, making the overall ride smoother.
Tire Problems to Look For
Responsible drivers take the time to notice how their tires handle when driving. They also know how to perform tire inspections themselves every month to check on tire tread and other anomalies. It's always best to pay attention to the road when driving to avoid pothole damage, but other problems are less noticeable and will lead to needing new tires.
While driving:
- Vibration or thumping: Unusual vibrations or thumping noises can indicate an out-of-balance tire with a tread that has a flat spot due to locking the wheels in a panic stop or a tire with a separated belt (see above).
- Pull to one side: While driving at a steady speed, a steering pull to one side may indicate an underinflated or damaged tire on that side of the car. An underinflated tire, a brake system or wheel alignment problem could also cause it.
During inspection:
- Check tire pressure: Using a tire pressure gauge, you can check your tires' pressure to ensure they connect properly with the road. Too much air pressure causes the tire's middle section to contact the road, increasing wear in the tread's center. Too little air pressure causes the tire's outer edges to contact the road, increasing wear on both tires' tread edges.
- Wear on one edge of the tread: This type of wear indicates worn suspension components or a wheel alignment problem.
- Erratic tread wear: Alternating high and low spots around the tread, called cupping or scalloping, may indicate a wheel is out of balance but is more often a sign that you need to replace worn struts/shock absorbers or other suspension components.
- Sidewall cuts and tears: Impacts with road debris and curbs can damage the rubber tire sidewalls. You can usually ignore cosmetic damage unless accompanied by a bubble or bulge (see below). However, if the cords of the tire carcass are exposed and damaged, bring your vehicle to your local auto repair shop to have the tire replaced.
- Bubble or bulge: A bubble or bulge on the tire sidewall or tread indicates one of the belts inside the tire has separated from those around it. Replace any tire with this type of damage as soon as possible.
Finding Quality Auto Repair When Replacing Tires
While it's good to know when to replace tires based on tread depth, accidents still happen. With a AAA Membership, you never have to worry about being stranded , roadside assistance is just a call away. AAA recommends taking your vehicle to the nearest auto repair shop for an immediate tire inspection if you suspect you might need a tire replacement.
FAQs About When to Replace Tires
Below, you'll find answers to frequently asked questions regarding when to replace your tires.
Do I need new tires if I'm using a spare?
Yes, you will need new tires if you're using a spare, but how long you can drive on a spare tire depends on the type you're using. Donut-type spare tires are meant to be driven on for no more than 50 miles, going no faster than 50 miles per hour. If all of your other tires are in good condition with ideal tread depth, you can simply replace the damaged tire with a new one.
However, if the remaining tires are also wearing down, either by showing low tread depth or other signs of damage, you should replace all four tires to maintain balanced braking and driving.
How long does a tire change (or replacement) take?
Replacing tires takes about 10 to 15 minutes per tire. If you replace all four tires, you can expect to wait for about 45 to 60 minutes.
Where to get tires replaced?
AAA recommends that you plan ahead for vehicle service by finding a trustworthy auto repair shop and technician before you need them. Tire shops specialize in tire replacement and offer many different brands and options. General auto repair shops can also replace tires, which is a great option if you must simultaneously take care of other car repairs or inspections.
Additionally, if you bought your car from a dealership, they have technicians and the proper tires to diagnose and replace worn-out tires and are often the best place to go if you're having tire problems soon after buying a new car.