What Are Wear Bars on Auto Tires? Here’s the Simple Explanation

Most states across America set the minimum legal tread depth on All-Season passenger vehicle tires at 2/32 inch to prevent accidents and to save lives. Although all tires lose traction as they wear, wet roads present the greatest danger.

Liquids are incompressible; consequently, without sufficient tread depth while traveling at highway speeds, water cannot escape fast enough. Under these conditions, hydraulic pressure lifts the entire vehicle, causing tires to float above the surface or aquaplane. When this happens, drivers lose control and accidents are inevitable. This is where wear bars play an important role in tire safety.

All-Season Tire Wear Bars

Summer or all Seasontiress sold in the United States are required to have wear bars with a height of 2/32 inch molded into the bottom of the tires’ treads across the tread’s width from shoulder to shoulder. Wear bars are evenly spaced around the tires’ circumference to act as easily referenced wear indicators.

These are designed to be visible from all angles when surface tread wear approaches to the legal limit. Therefore, to be safe, replace your tires before the treads wear down flush with the wear bars.

Snow Tire Wear Bars

Since worn tires lose traction on snow-covered roads, many motorists living south of the Mason Dixon line tend to avoid the expense of fitting winter tires, and instead, use tire chains if necessary.

However, vehicle codes in many northern states mandate the use of snow tires between late-December and mid-March. Snow tires come with extra deep tread depths together with open tread designs. Standard snow tire wear bars are set at a height of six thirty-seconds of an inch to provide sufficient traction on snow covered surfaces.

Tread Measurement

For optimum tire management, use United States coins to measure tread depth if you do not own a specialized tread depth gauge. If your tires are fairly worn, insert a penny into each tread across the width of your tire while holding the coin flush against the side of the tread nearest you.

If Abraham Lincoln’s hair is covered by the tread surface, tread depth is greater than two thirty-seconds of an inch. If the tire has moderate tread depth, insert a quarter into each tread across the width in turn. If the top of George Washington’s head is covered, there are over four thirty-seconds of an inch of tread depth remaining.

Repeat this exercise with the opposite face of a penny if you wish to gauge tread wear on newer tires; If the top of the upside-down Lincoln Memorial is below the tire surface, you have more than six thirty-seconds of an inch of usable tread depth.

Repeat the relevant exercise at several points around the perimeter of all four tires to ensure that your tires are worn evenly. If not, have the wheels balanced and the steering geometry checked as soon as possible.

Safety First

To be on the safe side, do not cut corners. Avoid the danger of aquaplaning in rainy weather by replacing your All-Season tires when the tread depth reaches four thirty-seconds of an inch. On the other hand, driving in snow can be tricky, especially if you have recently migrated north from a warmer state.

Even if your vehicle is equipped with snow tires, when they become worn past a certain point, they tend to slip and slide regardless of vehicle speed. When driving on snow-covered roads, your tires must bite into and compress the snow to enable the treads to maintain contact with the surface. In addition, the treads must be deep enough to release trapped snow during every tire revolution.

If the treads do not clear themselves, traction and loss of braking power become dangerously impaired. For optimum results, don’t wait until the wear bars are flush with the surface; Replace your tires as soon as the tread depth is less than eight thirty-seconds of an inch.