Tread depth is the vertical measurement between the top of the tread rubber to the bottom of the tires deepest grooves. 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, depending on the tire. 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 penny test is a simple way to check whether you’ve hit the 2/32” threshold. To perform the penny test, 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. If you can see the top of Lincolns head, your tires tread depth is less than 2/32” and its time to replace the tire. When performing the penny 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.

Other ways to check tire tread depth include using a tread depth gauge, which can be found at your local auto parts store. A tread depth gauge is a simple graduated probe gauge that you insert into the groove and push the shoulders flush with the tread. Check the top of the gauge to see the measurement. Alternately, a small ruler can be used. Be sure to check in various locations, as a misaligned wheel may result in uneven tread wear.

In summary, tread depth is the vertical measurement between the top of the tread rubber to the bottom of the tires deepest grooves. New tires typically come with 10/32” or 11/32” tread depths, and the U.S. Department of Transportation recommends replacing tires when they reach 2/32”. The penny test is a simple way to check whether your tires tread depth is less than 2/32...