Measuring Tread Depth
Tire tread depth measures the height of the line extending from the deepest part of the tread void to the top of the tread block. This indicates the amount of remaining tread. Regularly checking your tire tread depth can help you determine when it is time to replace your tires.
Below are three common ways to check your tread depth:
Tread Depth Gauge
Find a quality tread depth gauge at an auto parts store or online. Some gauges are shaped like needles, where a probe extends out of the end of the gauge’s barrel to measure the tread depth of your tire’s circumferential grooves.
Carefully evaluate your tire to find the lowest, most worn area along the tire’s tread, and place the probe end of your tread gauge into the void between the tread blocks. Gently push down on the gauge’s handles until the handles meet the top of the tread blocks and stops. This will cause a bar to extend out from the opposite end, toward you. Remove the tread gauge to check the tire tread depth reading.
Because tires can wear unevenly, Discount Tire recommends that you check your tread depth in multiple spots.
Tread Wear Indicator Bars
Your tires contain wear indicators built into the tread. Look for a bar molded into the bottom of the tread void, in the circumferential grooves. These bars are raised to 2/32nds of an inch. When your tread blocks wear to become level with these bars, they are completely worn out and need replacing.
Coin Tread Depth Test:
The quarter test can show if your tread depth has worn to or below 4/32nds of an inch. To perform the quarter test, take a quarter and place it into your tread groove with George Washington’s head facing downward. If you can see the top of Washington’s head, then your tires have worn below 4/32nds of an inch. Tire tread below this depth greatly reduces your stopping ability and hydroplaning resistance.
Discount Tire recommends replacing tires worn at or below 4/32nds.
The penny test can show if your tread depth has worn below 2/32nds of an inch. Perform the penny test by placing the penny into the tread groove with Abraham Lincoln’s head facing down. If you can see all of Lincolns’ head, the tires are completely worn out. However, passing the penny test shouldn’t determine whether you keep your tires. Even if your tires pass the penny test, they can still be worn below the 4/32nds threshold, at which safety and performance suffers.
We recommend that you replace tires worn below this limit, so visit your local Discount Tire for your best new tire options.