Name of test for checking tire tread?

The test for checking tire tread depth is commonly referred to as the "penny test." To perform this test, insert a penny into the tire tread with Lincoln's head facing down; if you can see the top of his head, the tread is too worn and the tire needs to be replaced. Other methods include using a tread depth gauge or the more advanced "quarter test," where you use a quarter instead of a penny for deeper tread measurements.