How to check tire wear with a coin

How to Check Tire Tread Depth: The Penny Test

When it comes to checking tire tread, there are a number of methods that can help you know if it’s time to replace a tire. Heavily worn tread will prevent a tire from performing as designed and can lead to unsafe driving conditions. One of the simplest, most common ways to check tread depth requires nothing more than a penny and a few moments of your time.


In the United States, tire tread depth is measured in 32nds of an inch. New tires typically come with 10/32” or 11/32” tread depths, and some truck, SUV and winter tires may have deeper tread depths than other models. The U.S. Department of Transportation recommends replacing tires when they reach 2/32”, and many states legally require tires to be replaced at this depth.

The idea of the penny test is to check whether you’ve hit the 2/32” threshold. Here’s how it works:

    Place a penny between the tread ribs on your tire. A “rib” refers to the raised portion of tread that spans the circumference of your tire. Tire tread is composed of several ribs.

    Turn the penny so that Lincoln’s head points down into the tread.

    See if the top of his head disappears between the ribs. If it does, your tread is still above 2/32” , If you can see his entire head, it may be time to replace the tire because your tread is no longer deep enough.

    When performing the penny tire test, remember not only to check each tire, but to check various places around each tire. Pay special attention to areas that look the most worn. Even if parts of your tread are deeper than 2/32”, you should still replace the tire when any areas fail the penny test.

    Consistent wear around the whole tire is normal, but uneven tread wear could be a sign of improper inflation, wheel misalignment, or a variety of other things. If you see uneven tread wear, you should have a technician inspect your vehicle.



    A simple way to check your tire tread depth is by using a tread depth gauge. You can find tire tread depth gauges at your local auto parts store. There are many models available, but an inexpensive simple graduated probe gauge will work just fine. All you have to do is stick the probe into a groove in the tread and press the shoulders of the probe flat against the tread block and read the result. All gauges should measure in both 32nds of an inch and millimeters.


    Another indicator of worn out tread already lives in your tires themselves. Every performance, light truck, or medium commercial tire comes equipped with indicator bars (or wear bars) embedded between the tread ribs at 2/32”. They’re there to help you monitor tread depth and make decisions about tire replacement. Just look to see if the tread is flush with the indicator bars. If they are, it’s time to replace the tire.


    While the penny tire test does deliver on what it promises – indicating whether tread has reached the legal limit – it may not be the best indicator of whether your tires are safe for the road. Tire performance can diminish significantly before your tread hits 2/32”. Even though the law deems fit for safe driving may not prevent you from hydroplaning or losing control in rainy, slushy conditions. If you think your tires may be close to needing replacement, have them checked out by a licensed mechanic.

    Got a Minute? How to Check Tire Tread Depth with a Penny

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    • Feb 12,2018

    When your tire treads wear thin, you could be in for a slippery ride—literally. Luckily, you can spot dangerous tread depth using only a penny, and Honest Abe’s face! The penny test is quick, easy, and can help you know exactly when to replace tires.

    The Penny Test

    To check your tread depth, you don’t need any fancy tools or expert knowledge. Grab a penny, and you have everything you need!

    1. Place your penny into a tread groove upside down. In other words, your penny should be going into the tread headfirst!
    2. Examine the part of the penny that’s showing. If you can see the top of Abe’s head, your tread is shallow.
    3. Repeat the penny test in several grooves of your tires. If you can always see the top of his head, your tire is worn and it’s time for a replacement!
    4. For reference, the distance between the top of a penny and Abe’s head is about 2/32nd of an inch. If you can see the top of his head, your tread is less than 2/32nd of an inch and your safety may be at risk. Depending on where you live, continuing to drive on such thin tread could actually be against the law.

      "Most states require a minimum of 2/32 of an inch (approximately 1.6 mm) of tread, but two require less, some have no requirements, and some defer to the federal criterion for commercial vehicle safety inspections," reports the National Center for Biotechnology Information.

      Why check tire tread depth?

      With adequate tire tread depth, your car is able to grip the road. This is especially important when roads are snowy or wet, or when you’re driving on less-than-ideal surfaces. Once tread becomes shallow, your tires are more prone to slipping and sliding, creating a dangerous situation for yourself and other drivers on the road.

      When your tires are worn, other components of your vehicle can begin to wear prematurely, too, as your vehicle experiences excess strain. While new tires can be a big investment, they’re an investment worth making.

      Check your tire tread depth today!

      Reach into your pocket and pull out your spare change. Give the penny test a try—it only takes a few minutes—and find out if it's the right time to replace your tires. If you're short on change, just find your nearest Firestone Complete Auto Care. Our stores offer free tire inspections that include tire tread depth measurement!

      Schedule an Appointment


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      How to check tire wear

      Tire wear in the United States is checked using a coin with the image of the first president of the country. A one-dollar coin is inserted into the groove of the tread with Washington's head down. If Washington's hair is visible, then it's time to buy new tires. A coin with a face value of 1 cent will also help to check the wear of automobile rubber. If the top of the Lincoln is visible, then the tires have reached the tire wear rate and must be replaced immediately.

      Tire wear can also be determined with a 1 euro coin. It must be inserted into that part of the tire where the tread is most worn. If the golden circle is in rubber, then the tire will still serve you. If the gold part of the coin is completely visible, then it's time to change the shoes of your car.

      Tire wear can also be determined using Russian money. The domestic 2-ruble coin must be inserted into the protector with the eagle's head down. If the top of the bird is visible above the surface of the tire, then the tire has not yet reached the end of its life.

      Tire wear

      Premature tire wear can be avoided. According to the Research Institute of the Tire Industry (NIIShP), the "life" of half of the tires is reduced due to improper operation. After all, the service life of rubber largely depends on driving style, road conditions, compliance with the load index and correct tire pressure. Therefore, it is not surprising that with the same model of car and “shoes”, the mileage of their tires can differ by several thousand kilometers.

      The main causes affecting premature tire wear

    5. failure to comply with the norm of air pressure in tires
    6. loading the car with a mass exceeding its load index
    7. inept driving
    8. untimely maintenance and repair of tires 9009
    9. wheel imbalance
    10. malfunction of the chassis and steering of the car
    11. For new tires, the break-in process is important. The first 200-300 kilometers of newly purchased tires should be extremely careful, especially in winter or in rainy weather. This is due to the fact that before vulcanization, the treads of new tires are covered with a separating layer, which should be erased only during operation. Therefore, all types of rubber must be run-in.

      Types of tire wear

      Tire wear occurs in a variety of ways:

      • small seal around the perimeter of the tread is formed in the presence of shock absorber defects
      • mid tread wears faster with high tire pressure
      • worn sidewall shoulders indicate low tire pressure
      • wear in the form of abrasions on one side of the shoulder of the tire occurs due to parking through the curbs
      • the tire flattens when parked for a long time. Therefore, the car should not stand on tires for months. Before storing the machine, it is advisable to increase the tire pressure to 3.0 bar. So you can avoid deformation of the tire
      • noticeable wear in some places of the tire appears after the wheels lock during hard braking
      • sharp edges on one side of the front wheel - the result of frequent driving on severe off-road

      Uneven tire wear

      Uneven tire wear is normal because the tire is subjected to uneven loads while driving. In this case, a new wheel balancing will help. In most cases, when sawtooth teeth form on the transverse grooves of the profile, it is necessary to use cruciform wheel balancing. But this will only help with the correct geometry of the axis. This will change the direction of the tire. The sawtooth teeth will gradually disappear, along with them the noise will also disappear.

      If the wheels with asymmetric tread pattern are changed regularly, every 10,000 km, uneven wear of all tires can be avoided. But the replacement must be done on one side. That is, the front right wheel should only change to the rear right, and vice versa.

      Car tire wear rates

      In 1992, a uniform wear rate for summer tires was established in Europe - the minimum profile depth for tires for cars, trucks and motorcycles is 1.6 mm. This requirement also applies in Russia. An exception to the rule are light wheels with a minimum tread height of 1 mm. But for wide-profile and summer tires, this rate is too small. With such a profile depth on a wet road, the tire will have poor handling. For safety reasons, summer tires should be changed already when the remaining profile depth reaches 2 mm (wide profile - 3 mm). Modern winter tires have a tread depth of 9, depending on the manufacturer.-12 mm. Permissible wear for them is 4-6 mm.

      Many modern tires have built-in wear indicators in the form of small rubber pimples. They are soldered into the base of the protector. When the tire wears down to acceptable limits, the pimples become flush with the tread. This means it's time to change the tire.

      In addition, the American tire marking uses the TWI (Tread Wear Indication) tread wear indicator. Sometimes it is indicated by arrows. The tire wear indicator is located evenly in 6-8 places around the perimeter of the tire.

      Tire wear percentage

      Over time, the life of the tire decreases, and at the same time, the percentage of wear increases. If the bead is damaged during installation, the percentage of wear increases to 10%. Chipping, chips, cracks on the tread increase wear by 25%. 100% wear is assigned to a tire with carcass delamination.

      The percentage of aging is added to the technical wear percentage. For 3 years of operation, the tire loses up to 10% of its resource. When using a tire for more than 5 years, the percentage of wear can reach 50%.

      How to determine the wear of summer tires

      In fact, the average life of any tire is 5-7 years, but a lot depends on how the owner treats his car. Aggressive driving, improper seasonal tire storage, unrepaired suspension/balancing problems, incorrect pressure and other errors can significantly shorten tire life. But worn tires can be a serious problem on the road: an increased risk of uncontrolled skidding, hydroplaning, even accidents is the price that drivers and passengers have to pay for using old tires.

      Tire wear index

      Each manufacturer indicates the so-called wear index on the tire profile, which most often looks like the inscription “Treadwear 100” and means a maximum of 48,000 km on a standard road surface (polygon). In a real environment and often not the most ideal roads, this number actually needs to be divided by 1.5 - we get 36,000 km.

      By analogy, if the wear resistance index is 150, then this means “factory” 72 thousand km, 200 - 96 thousand km., and so on.

      What are the dangers of worn tires on the road:

      • adhesion to the roadway deteriorates, which leads to an increased likelihood of skidding, accidents, hydroplaning in case of rainy weather;

      • reduced cross-country ability in off-road conditions;

      • increases the risk of a tire puncture while driving.

      It is also worth remembering that the issue of tire wear is regulated by traffic rules, and you can get a fine for using “bald” rubber. Knowing what maximum tire wear is acceptable, this is easy to avoid: 1.5-2 mm for summer, and 4-5 mm for winter (a more accurate figure is indicated by the manufacturer).

      3 ways to determine tire wear

      1. According to the wear indicator on the tire. To find this indicator, you need to inspect the side of the tire and find one of the markings: a triangle, a company logo, a snowflake, or the abbreviation TWI. If the tread has worn down to this indicator, it means that the tire needs to be disposed of urgently.

      2. Many people in the old fashioned way prefer to use a 10-kopeck coin. Insert it into the tread with the inscription "10 kopecks" towards you, and if it is visible, the wear level is too high, you need to replace the tire. This method is convenient, but not entirely accurate: by measuring wear in different parts of the tire in this way, it will be difficult to estimate its unevenness by eye, and this is also an extremely important indicator.

      3. It is optimal to use a special gauge, depth ruler or caliper for these purposes. This will allow you to measure the wear of the tread in different parts of the tire with an accuracy of up to a millimeter and understand if there is uneven wear.

      Uneven tire wear: how to determine the causes, what is dangerous

      If measurements show different results in different parts of the tread, it is important to determine exactly how your tires wear in order to understand where and what the operating error is.

      If the tread wears more on the sides and the center wears off less, this means that the tire pressure is insufficient and the contact patch with the road is not correct. This leads not only to poor vehicle stability, but also to increased fuel consumption.

      If the tread is worn down the middle but the sidewalls are fine, then your tires are overinflated. Sometimes this is done intentionally in order to save fuel, but in this case, the tires will still have to be changed ahead of schedule.

      There is also the possibility of increased wear on the inside or outside of the tread - this indicates an incorrect camber. A visual table with wear options and their causes:

      How to assess tire wear visually: additional parameters

      • Cracks on the sides of tires can indicate frequent off-road driving, improper storage, low-quality rubber or long service life, as well as incorrect tire pressure.

      • Bulges or "hernias" on the sides of the tires appear as a result of the side part hitting hard obstacles. Tires with such damage are not recommended.

      • Dents on the tread indicate insufficient depreciation and unadjusted camber. Having found such damage, it is necessary to drive the car to the service and make sure that the suspension is in good condition.

      • Individual wear spots on the tread indicate aggressive driving / braking, skidding with wheel locks, or prolonged parking of the car in one position.

      How to calculate tire wear percentage

      Most often, this is required for the sale and purchase of used tires in order to orient the buyer in the degree of their wear. Many sellers give this figure at random, but this method has nothing to do with the actual assessment of the degree of tire wear. It is also important to understand that a conditional 50% wear for a summer tire is an acceptable value, while 50% wear of a winter tire tread is a sign that the tire cannot be used. Therefore, it is important to know how to accurately determine the percentage of tire wear so as not to get into an unpleasant situation.

      Many people divide the actual tread height by the height of the same, but new tire, and get a certain percentage of wear. This would be correct, if not for one BUT: we cannot physically erase the tread to zero, and the law prohibits the use of tires with a tread below the permitted values.

      You can calculate actual tire wear by dividing the difference between the new tire height and the actual tire height by the difference between the new tire tread height and the minimum possible tread height for that tire, and then multiplying this number by 100.

      If it is impossible to find out the height of the same, but with a new tire, use the average values ​​​​of your tire type:

      Tire type

      Average tread height at start of use

      Winter tires with Scandinavian tread

      10 mm

      Winter with regular or asymmetric tread

      9 mm

      High-speed winter

      7 mm

      Summer tires with classic tread

      8 mm

      Summer speed

      7 mm

      You can check summer tires for wear a little less often than winter tires, since in summer the tread depth is not so important for patency.

      Learn more