How to Check Tire Tread Depth

Safe braking, accelerating, and steering all require traction between the tires and the road surface. And in the US, around one in four vehicles on the road has at least one tire that’s worn out and needs to be replaced. It’s a concern that could lead to an accident or harrowing blowout.

Tires aren’t the least expensive parts to replace, and it’s understandable that you might want to prolong that expense as long as possible However, it’s important to know how to check tire tread depth. It serves a few purposes:

  • To identify worn-out tires that need to be replaced
  • Uneven wear helps identify potential steering or suspension problems
  • To know when to rotate the tires and the best position to put them in

For either no cost at all or for the minimal cost of a tread depth gauge, you can keep an eye on your tires.

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Why Tread Depth is Important 

The difference in handling between new tires and only 2/32nds of an inch of tread remaining can be significant. New tires have a full depth of tread, often between 8/32nds and 12/32nds, which provides excellent traction and grip on the road. This means that they will handle better in wet or slippery conditions, and will have better braking performance. 

Tires with 2/32nds of tread, on the other hand, have reduced traction and grip on the road, especially in wet or slippery conditions. Braking performance is affected as the tires will can’t displace as much water as new tires, leading to longer stopping distances. Tires with less tread will also generate more heat which can lead to increased wear and tear on the tires, and potentially even cause a blowout. 

The reduced handling and traction of worn tires also increase the risk of hydroplaning because the channels between the tread blocks as well as the sipes are much smaller. Water or snow gets trapped between the tire and the ground, creating a slippery barrier that prevents contact. 

It’s important to have tires with enough tread depth to ensure the vehicle’s safety on the road. That’s why it’s recommended to replace tires when the tread depth reaches 4/32nds of an inch. They’re completely worn out when there’s just 2/32nds of an inch of tread depth remaining or when the tread wear indicator is visible. 

How to Measure Tire Tread Depth 

There are a few common and free or inexpensive methods for checking how much tread depth remains. Two of the three tests only involve pocket change. 

1. Perform the Penny Test

The penny test is a simple and easy method to check the tread depth of your tires to determine if your tires need to be replaced or if they are still safe to drive on. The test is done by inserting a penny between the tread blocks.

To perform the penny test, start by finding the tread wear indicator on your tires. These are small raised bumps that are located in the grooves of the tread. They are usually located at the base of the tread and are designed to let you know when your tires are worn down to the minimum legal limit.

Once you have located the tread wear indicator, take a penny and insert it into the groove of the tread with Lincoln’s head facing down. If the top of Lincoln’s head is visible, then your tread depth is less than 2/32 of an inch, which means it’s time to replace your tires. If the top of Lincoln’s head is not visible, then your tread depth is greater than 2/32 of an inch, and your tires would likely pass a state inspection.

The penny test should be done on multiple locations of the tire, both in the center and at the edges, as the tread depth can vary across the tire.

2. Perform the Quarter Test

The quarter test is another simple and easy method to check tread depth. Similar to the penny test, it is a quick way to determine if your tires need to be replaced or if they are still safe to drive on using a quarter.

To perform the quarter test, take a quarter and insert it into the groove of the tread with George Washington’s head facing down. If the top of George Washington’s head is visible, then your tread depth is less than 4/32 of an inch, which means it’s time to replace your tires. If the top of George Washington’s head is not visible, then your tread depth is greater than 4/32 of an inch and your tires are safe to drive on.

3. Use a Tread Depth Gauge

Tread depth gauges are a cost-effective tool for measuring the remaining tread depth. They’re usually equipped with measurements in both fractions of an inch or millimeters, whichever you prefer. A t-shaped frame has a small measuring stick like a caliper that can be extended for extremely accurate measurements, and it’s the best way to check tread on all tires, especially newer ones with plenty of depth remaining.

Place the flat section against the tread, spanning two tread blocks, then press the stick downward until it presses against the tire. Read the measurement and repeat in several spots around the tire.

If one or more tires have less than 4/32nds of an inch of tread depth remaining, it’s time to consider changing them. Replace tires in pairs, and be sure to match the size, type, and speed rating of your old tires. You can get the parts you need at your local AutoZone Store. If the job is too big for you, seek out one of our Preferred Shops to help you do the job.

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FAQ/People Also Ask

How to measure tire tread depth

You can measure tread depth using a penny or a quarter, but the most accurate measurement is by using a tread depth gauge.

How do I know if my tire tread is 4/32nds?

Insert a quarter between the tread blocks with Washington’s head pointed downward. If you can see the top of his head, the tread is less than 4/32nds remaining.

Is the penny test for tires accurate?

The penny test is accurate for determining the depth related to 2/32nds of an inch. However, it can’t tell you how much more (or less) there might be.

How do you check your tire tread at home?

You can check your tread at home with a tread depth gauge, or use the penny test or quarter test to assess the depth.

How do I know if my tire tread is good?

If your tires have 2/32nds of an inch or more, they will pass most state inspections. However, the general rule is that you need 4/32nds of tread depth remaining for safe driving.

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