Tread Depth: Why It Matters and How to Measure It

Mild Changes For New Volvo 90s

When it comes to stopping power, many drivers tend to focus on their brakes. However, our tires are where the rubber meets the road. Having good brakes isn’t enough; we need to have tires with enough traction to turn braking power into actual stopping power. If the tire tread depth isn’t deep enough, your tires can lose their grip on the road, leading to longer stopping distances.

How Does Tire Tread Work?

To understand how tire tread works, let’s focus on how it helps you stop in wet conditions. To have good contact with the road, the tire has to be able to move the water out of the way. If it can’t, the tire will ride on top of the water’s surface, instead of the surface of the road. This can lead to “hydroplaning”, a potentially dangerous situation that reduces the ability to steer and brake.

Each tire has channels for the water to flow through, known as tread, which helps move the water out of the way. Take a look at your tires, and you’ll see the channels run around and across them. The tread is designed to direct water away from the tire so that the tire can grip the road better.

The deeper the channel, the more water it can move. Brand new tires have very deep channels, allowing them to move a good amount of water with ease. As the tire wears down, the channels become shallower and can move less water. Once they’re worn down enough, it can seriously affect your ability to stop on wet roads. According to the National Highway Traffic Safety Administration (NHTSA), approximately 11,000 accidents occur annually from bald tires.

How Much Tread Should My Tires Have?

Since tire tread wears down, it’s important to monitor the tread depth of your tires. Washington state law requires drivers to have a tire tread depth of 2/32 of an inch or more. However, Consumer Reports and other advocate groups recommend replacing your tires when the tread is worn to 4/32 of an inch or 3.2 millimeters.

Once the tread depth is worn to 2/32 of an inch (1.6 millimeters), the tread wear bar will be visible. The recommended standard has twice the tread depth as a completely worn-out tire—and that additional tread makes a huge difference. A safe stopping distance from freeway speeds could result in a crash with bald tires.

4 Ways to Check Your Tire Tread

Fortunately, there are four quick and easy ways to check your tire tread, and they can all be done from home.

  • The Penny Test

Take a penny and insert it into the tread with Lincoln’s head upside down and facing you. If you can see all of Lincoln’s head, it means you have less than 2/32 inches of tread left; it’s time to replace your tires.

  • The Quarter Test

The quarter test works exactly the same as the penny test. Put the quarter into the tread, with George Washington upside down and facing you. If the tread touches his head, you have at least 4/32 inches of tread left. If the tread doesn’t cover Washington’s hairline, schedule a tire replacement appointment.

  • The Tread Wear Bar Indicator

Most tires have tread wear bar indicators, which are evenly spaced through the main grooves in the tire’s tread. When the tread is worn down enough that it’s flush with the wear bars, the tires should be replaced.

If you use winter tires, it’s important to know that they have deeper tread depths than all-season or summer tires. The winter wear indicators help you see whether you have suitable tread depth for driving in the snow or other wet, slippery conditions. The wear bars will be visible once the tread has worn down to approximately 5/32 inches. Although the tires may have a legal amount of tread left, they may not provide the traction you need for winter driving.

  • Tread Depth Gauge

Tread depth gauges are an easy way to accurately measure your tire tread depth. You can find them in almost any auto parts store. To measure the depth of your tread, insert the gauge’s probe into the tire’s tread grooves; press the gauge down and then read the results.

In general, it’s recommended to check your tread depth every 3,000 miles or once the tread reaches 4/32 of an inch deep.

Since tires can wear unevenly, it’s always a good idea to check the tread depth at various spots on the tire. While checking your tread, make sure to inspect your tires, too. Pay attention to things like whether the wear is uniform or if there are any signs of damage, like cracking, bulging, or other signs of wear. Even if you have adequate tread depth, excessive wear can cause a tire to fail.

Time to Replace Your Tires? Head Over to EuroCar Service!

Replacing your tires as soon as they’re worn is the best way to protect yourself and your passengers from accidents or blowouts. At EuroCar Service, we offer a wide selection of tires to choose from. If you’re unsure whether you need new tires, we’re happy to take a look and give you recommendations.

We also offer every service you need to keep your vehicle’s wheels and tires in excellent shape, including new tire installation, balancing, rotations, and more. Our ASE-certified technicians specialize in all European makes, including Audi, BMW, Mercedes, Land Rover, Mini-Cooper, Saab, Jaguar, Volkswagen, Volvo, Smart Car, and Fiat. Call us today at 206-527-8828 or request an appointment online.