As you’ve probably noticed, tires aren’t completely smooth. They have tread blocks, which is what we call the pattern on the tires made up of raised parts of the rubber that actually come in contact with the ground, and the tread grooves which are the indents in the tires. Tire tread is really important for maintaining traction on the road, preventing blowouts, and avoiding hydroplaning. The US Department of Transportation says you should replace your tires if the tread wears down to less than two 32nds of an inch (2/32”). If you’re driving in an area that has a lot of rainfall and wet roads, you might want to consider keeping your tread at 4/32nds of an inch to increase traction with the road. When in doubt, your car’s owner manual should also have the recommended tire tread for the manufacturer tires listed.
If you’re having a hard time picturing how long an awkward measurement like 2/32nds” is, we’re right there with you. The good news is that you don’t need an expert (or even a ruler) to check tires and determine if your tread is deep enough. All you need is a penny!
Testing Tire Tread With a Penny
The penny test is an easy way to check tire tread and see if you need new tires soon. To do it, take your penny and stick it into a random groove in one of your tires. Position it so that Abraham Lincoln’s head is pointing down into the tread. Sorry, Abe. If you’re trying to check your tire tread for 4/32″, you’ll want to do a quarter test instead.
Reading the Results
If the top of Abe’s head disappears into the groove making him look bald, your tread is in great shape. Congrats! If you can still see his whole head sticking out from the tire (or it’s just skimming the top of his beautiful hair), that means your tires are worn down and should be replaced soon. And that’s all you have to do to check your tire’s tread depth with the penny test! If you’re using the quarter test, the tread should come up to the top of George Washington’s head.
Newer tires also have indicator bars that can help you keep track of how worn your tires are. These are basically small bars built into the tires that start to reveal themselves among the remaining tread as your tires start to wear down. They make tire maintenance and measuring your tread a lot easier.
Check Each Tire
Test a few different areas on each of your tires. While you’re down there, take note if any tires or spots seem much more worn out than others. This could be a clue that your wheels aren’t correctly aligned or the tire isn’t properly inflated. You might also want to use a tire gauge or TPMS system to check your tire pressure and make sure you don’t have any small leaks. Bring this to the mechanic’s attention when you go to get your tires replaced (don’t forget to see if you have tire warranties for the replacement!).
There you have it. Lincoln will tell you if you need new tires, and he cannot tell a lie! Oh wait, that was Washington… Either way, now you know how to measure tire tread.