The Penny Test is the gold standard for measuring tire tread-depth because it is easy and it works. Just take a penny and with Lincoln's head upside down, put it between th tread blocks of the tire. If you are not able to see the top of Lincoln's head - if his head is "buried" between the tread blocks - then you still have more than 2/32 of an inch of tread remaining. If you can see the top of Lincoln's head, it's time to go tire shopping because the tread is worn down to or beyond 2/32 of an inch
