What Are Wear Bars on Auto Tires?by Jody L. Campbell
All tires manufactured today have wear bars. These wear bars are located in between the tread pattern and are used to identify tire wear. The wear bar is molded slightly higher than the lowest point in the tread pattern that would render the tire with zero tread.
Tire wear bars help to determine the amount of tire tread left. Since the tread of the tire is what creates traction, it is important to have the tires inspected and their life expectancy determined during every maintenance service performed on the vehicle.
Tread wear bars are located in between the tread pattern directly across the width of the tire. They appear every six to 10 inches (depending on the size of the tire) throughout the entire circumference of the tire, so an inspector can determine if one part of the tire is closer to the wear bar than another. This could indicate a bad belt in the tire or other problems creating unusual tire wear.
A wear bar is 2/32 of an inch high. This means when the tire tread gets to the point of the wear bar, only 2/32 of an inch of tread wear is left on the tire. While this may be OK for dry driving conditions, it can be potentially hazardous when driving in inclement weather.
The tread wear bar on tires was mandated to be on every tire manufactured in the United States on August 1, 1968.
When inspecting the tire tread wear bars, compare the depth of the tread using a depth gauge and check in several locations around the circumference of the tire. Check also for uneven edge wear on the tire, which would indicate lack of rotation or the need for an alignment.