Tire Wear Bars: What They Are And Why They're Important

National Tire Safety Week is one of Car Talk's favorite weeks of the year. In observance of NTSW, we decided to take a closer look at tire wear bars and tire safety. Vehicle owners have a responsibility to ensure the tires they have on their vehicle are safe for themselves, their passengers, and those around them in traffic.

Ensuring your tires are safe is an easy three-step process. Check the pressure, look for damage or uneven wear, and check the remaining tread. In this story, we will focus on how drivers can quickly and easily determine if their tires have enough tread left to be considered safe. You won’t need any tools to check this, not even a penny.

What Are Tire Wear Bars?

To make it easy for vehicle owners and mechanics to inspect tires for proper tread depth, manufacturers mold visual guides right into the tread. Called tire wear indicators or tire wear bars, these make it very easy to simply look at a tire to determine if it has enough tread remaining to be considered safe in all road conditions.

If you look at our image above, you will see that across the tread from left to right are bars in the tread grooves. Those are the tire wear bars staring right up at you. If the tread has not yet reached the level of the bars, your tires are safe. Your inspection is not entirely done since you have not looked for damage or checked the tire pressure. However, you do know that your tire has not yet worn out its tread.

Where Are Tire Wear Bars?

Tire manufacturers want you to be able to look at the tire and see the wear bars, so they are molded across the length of the tread in numerous places. In other words, if a tire’s circumference is 360 degrees, you will find the wear bar every quarter turn or about every 90 degrees or so.

When your mechanic puts your car on a lift, she can simply glance at the tire to see tread wear bars. If you are looking at your tires in your driveway, you can see them if you look at them from the top down or if you turn a front tire and look at it from the sides. You need to see the full width of the tread.

What is Tread Depth?

Tread depth is simply how much depth is between the top of the tread the tire rides upon and the lower section of the tire’s construction, a.k.a. the grooves in the tire. A typical new all-season touring tire has about 8mm of tread depth. An all-terrain tire or winter tire may have much more, and a high-performance summer-only tire may have a bit less tread depth when it's brand new.

Mechanics and drivers can use an inexpensive and simple-to-use tread gauge to measure tread depth. The tool has a small pointer that goes into the tread gap when pressed and then provides a readout. The readout can be viewed in either millimeters (mm) or 32nds of an inch. All-season tires are considered worn when 2/32” of tread is remaining (which equates to about 1.6mm).

Bear in mind that this is for all-season tires. Many winter tires come with two sets of wear bars. The first higher level is “safe for winter” and the second lower level is “safe for three-season usage.” It is very important to know that all of the tread bars need to have more than the indicated tread wear to be safe. It is not uncommon for tires to wear unevenly. Once any one of the tread bars is flat to the tread, replace that tire and consider the others for replacement as well.

Why Are Tread Wear Bars Important?

Tread wear bars provide an easy-to-use method of determining if tires have enough remaining tread to be safely used for the type of driving they were designed to handle. At a glance, an owner or mechanic can tell if tires have the tread needed to be safe or if they should be replaced.

Do All Tires Have Tread Wear Indicators?

All tires have tire wear bars, but some are more helpful to drivers than others. Our favorite wear bar indicators may be the ones on the Eagle Exhilarate tire. To make it perfectly clear when the tire should be replaced and recycled, Goodyear molds in a message to owners. “Replace by 2” is clearly visible on the tire.

What is the Best Way to Check Your Tread Wear?

The best way to check your tires for wear is to see the entire tread footprint, not just the outward-facing tread, which you might see if standing beside the vehicle. Front tires are the easiest because you can turn the wheel and thus expose the full tread. Rear tires will require you to have the tire removed, use a lift, or to get low enough to see behind the tire.

Our image above shows how the tread is not yet fully worn according to the four wear bars. However, on the right side of the tire, we can see that the tire has suffered from the car being misaligned, and the tread is so far gone we can even see reinforcement fibers! This tire is overdue for being replaced and is unsafe. Tread wear bars are a tool, but they are not the only way to tell if a tire is in need of being replaced. Damage or uneven wear are also visual indicators you must take note of.

What Are Car Talk's Top Safety Tips For Tires?

If the vehicle is new to you, inspect the tires to ensure they are the right type. Don’t drive on high-performance summer-only tires below 40F, and never drive on a studded winter tire in the summer. If you drive in harsh winter weather, purchase winter tires that display the three-peak mountain snowflake symbol. Here is a punch list of ways you can take an active role in making sure your tires are safe:

• Learn how to check the air pressure in your tires. Most new cars have the ability to display the pressure on your gauge cluster.
• Rotate your tires according to the manufacturer’s guidelines. Some EVs, like popular Tesla models, require rotation every 6,250 miles or sooner.
• Have a flat tire plan - Roadside assistance, a spare tire, an inflator kit, and tire tools should be part of this.
• Inspect your tires once each season and before any road trip at a minimum.
• If your car has a spare tire, ensure it is properly inflated at your oil change visits.
• When your vehicle is inspected during routine service, always take note of the remaining tire life reported by the mechanic.
• Never “plug” a flat tire. If your tire is punctured, have a qualified repair shop employ the proper method of repair (plug and patch).
• Never repair or re-use a tire that has been driven on while deflated.
• Know the ages of your tires. After 6 years of use, have them replaced regardless of tread depth.

For more information on tire wear bars and tire safety, read what our friends at SimpleTire have to say about the subject.

Read more on the Best Tires in the Industry here.

Read more on Tire Safety and Mainenance here.