Tread Depth Gauge 101

Written by

CarParts.com Research Team

Automotive and Tech Writers

Updated on December 10th, 2024

Reading Time: 4 minutes
Summary
  • A tire tread depth gauge is a tool used to measure a tire’s tread depth.
  • To use a tread depth gauge, you first have to zero it out. Then, you have to place the measuring pin into the tread groove and check the reading. You’ll have to repeat this process at least two more times to get the average tread depth.
  • In most US states, the minimum legal tire tread depth of passenger cars is 2/32 of an inch. This can still vary, depending on where you live and the type of vehicle you drive.
  • If your vehicle’s tire tread depth goes below the minimum legal tire tread depth, you could face penalties, fines, and points on your driving record. In the worst-case scenario, you might even get into an accident before a police officer notices.

As the contact point between your vehicle and the ground, your tires should always be in good condition. Over time, however, tires will naturally wear and lose their tread depth, which is what gives your tires their grip. When its tread depth gets too thin, the tire loses grip, affecting braking distance and handling. Luckily, you can make sure your vehicle’s tire tread depth never gets to that point by regularly measuring it with a tread depth gauge.

What Is a Tire Tread Depth Gauge?

As its name suggests, a tire tread depth gauge is a tool used to measure a tire’s tread depth. Tire tread depth gauges come in different designs, with some equipped with a dial for easier reading. You can also find digital tire tread depth gauges with a large LCD screen that displays the tread depth rating.

In most US states, the minimum legal tire tread depth of passenger cars is 2/32 of an inch.

How To Use a Tire Tread Depth Gauge

Using a tire tread depth gauge can be a little confusing at first, but it gets easier once you understand the basics. Here are helpful tips on how to use a tread depth gauge:

Zero Out the Tread Depth Gauge

Before you insert the gauge into the groove, you’ll have to zero it out first. Push the tread depth gauge against a flat surface until the measuring pin slips into the barrel. If the gauge reads 0/32, then you can now move on to the next step.

Place the Measuring Pin Into the Tread Groove

Now it’s time to place the tread depth gauge in the very center of the tire’s main tread groove. Gently push down on the gauge until the base hits the tread.

Check the Tread Depth Reading

Carefully remove the gauge, and note the measurement indicated on the gauge. Keep your hands on the barrel, so you don’t accidentally touch the measuring pin.

Repeat the Process Two More Times

One reading isn’t going to be enough to truly get an accurate measurement of your vehicle’s tire tread depth. Uneven treadwear is common among misaligned wheels, so it’s best to repeat the first three steps at least two more times. Insert the measuring pin at different points of the tread groove, with around 15 inches in between each point.

Compute for the Average Tire Tread Depth

To get the average tread depth, add all three of your readings, and divide the total by three. The answer is the average tire tread depth, which you can now compare to the tire’s original specs.

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Why Is Measuring Tire Tread Depth Important?

In most US states, the minimum legal tire tread depth of passenger cars is 2/32 of an inch. This can still vary, depending on where you live and the type of vehicle you drive. For example, most states will require larger vehicles such as buses and trucks to have a tread depth of at least 4/32 of an inch.

Any less than that, and you’re likely to get pulled over. You could face penalties, fines, and points on your driving record. In the worst-case scenario, you might get into an accident before a police officer notices. Balding tires have less grip on the road, which means you’re much more likely to get into an accident.

For your own safety, it’s best to inspect your tires regularly, so you can replace them before it’s too late.

How Much Does a Tread Depth Gauge Cost?

Tread depth gauges are relatively affordable, with some selling for as cheap as $10. However, if you’re looking for a branded, high-quality gauge, then you might have to shell out around $260.

How To Gauge Tire Tread Depth

Using a tire tread depth gauge isn’t the only way you can measure your tire’s tread depth. In fact, there are several other methods you can try, just in case you forget your gauge at home.

Perform a Penny Test

The most popular method is performing a penny test, where you insert a penny into your tire’s tread groove. With Lincoln’s head upside down and facing you, check to see how much of his head is exposed. If you can see all of his head, then this means you need to replace your tires as soon as possible.

Use a Quarter

If you’re out of pennies, you can use a quarter too. Insert the coin into the tread groove, and check if the tread is touching Washington’s head. If Washington’s head is exposed, then your tires need replacing.

Check the Tire Tread Wear Indicator

Printed around the bottom of the tread groove, you’ll find the tire tread wear indicator. As the tread wears down, it’ll slowly become even with the indicator. Once this happens, it’s a sign that you need to replace your tires.

Written By CarParts.com Research Team

Automotive and Tech Writers

The CarParts.com Research Team is composed of experienced automotive and tech writers working with (ASE)-certified automobile technicians and automotive journalists to bring up-to-date, helpful information to car owners in the US. Guided by CarParts.com's thorough editorial process, our team strives to produce guides and resources DIYers and casual car owners can trust.

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