What Is Tire Tread Depth and How to Check It?

How To Tell If You Need New Tires?

When it comes to checking tire tread, there are a number of methods that can help you know if it’s time to replace a tire. The heavily worn tread will prevent a tire from performing as designed and can lead to unsafe driving conditions. One of the simplest, most common ways to check tread depth requires nothing more than a penny and a few moments of your time.

The Penny Test

Place a penny headfirst into several tread grooves across the tire. If you always see the top of Lincoln’s head, your treads are shallow and worn. If this is the case, your tires need to be replaced. If part of Lincoln’s head is always covered by the tread, you have more than 2/32 of an inch of tread depth remaining.

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, and 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 idea of the penny test is to check whether you’ve hit the 2/32” threshold.           

When performing the penny tire 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.

Consistent wear around the whole tire is normal, but uneven tread wear could be a sign of improper inflation, wheel misalignment, or a variety of other things. If you see uneven tread wear, you should have a technician inspect your vehicle.

Other ways to check Tire thread

Tread depth gauge

A simple way to check your tire tread depth is by using a tread depth gauge. You can find tire tread depth gauges at your local auto parts store. There are many models available, but an inexpensive simple graduated probe gauge will work just fine.

All you have to do is stick the probe into a groove in the tread and press the shoulders of the probe flat against the tread block and read the result. All gauges should measure in both 32nds of an inch and millimeters.

Tread Wear Indicator Bars

Another indicator of worn-out tread already lives in your tires themselves. Every performance, light truck, or medium commercial tire comes equipped with indicator bars (or wear bars) embedded between the tread ribs at 2/32”. They’re there to help you monitor tread depth and make decisions about tire replacement. Just look to see if the tread is flush with the indicator bars. If they are, it’s time to replace the tire.

Why Check Tire Tread Depth?

With adequate tire tread depth, your car is able to grip the road. This is especially important when roads are snowy or wet, or when you’re driving on less-than-ideal surfaces. Once tread becomes shallow, your tires are more prone to slipping and sliding, creating a dangerous situation for yourself and other drivers on the road.

When your tires are worn, other components of your vehicle can begin to wear prematurely, too, as your vehicle experiences excess strain. While new tires can be a big investment, they’re an investment worth making.

Why Worry About Tread Wear?

The most important reason to worry about tread wear is safety.

When your tire treads are worn, your car may respond poorly to adverse weather conditions like rain and snow. With good treads, your car will grip the road better. Also, having insufficient tread is considered illegal in many states. And finally, worn treads can make other parts of your car wear prematurely.

Potential Problem Areas:

  • Excessive wear in the center tread indicates over-inflation of the tire.
  • Excessive wear on shoulders may signal problems such as under-inflation of the tire.
  • Uneven tread wear indicates poor wheel alignment.
  • Excessive wear on one side of the tire signals an incorrect camber angle.
  • If the treads on the outer section become knobby, it may signal problems with the toe-in value