Tire Detreading/Tread Separation

Recent highly publicized cases related to the failure of Firestone tires on Ford Explorers drew national attention to the issue of tread separation. However, Firestone is not the only manufacturer to produce tires with tread separation problems. In fact, most other manufacturers have had similar problems including Continental, Goodyear, Cooper, Uniroyal-Goodrich and others.

Tires are constructed in layers, a simplified explanation of which follows. The inside liner of the tire is covered by the radial body piles that are themselves overlaid by steel belts. The outermost rubber layer of the tire that we all see on our cars and trucks is called the tread. In some tires, there is a nylon overlay system that sits in between the steel belts and the tread. In the tire industry, this nylon overlay system is referred to as a “safety belt.” The safety belt system is much safer and is currently used in high-end American tires and in most European markets. In tires without the nylon overlay system, the tread will sit on top of the steel belts and will be bonded to them with a rubber adhesive compound.

Tire detreading, also referred to as tread separation, occurs when the outermost tread of the tire suddenly separates from the layers under it. When a tire loses its tread, it can cause a rapid decrease in tire pressure or may lead to the tire rupturing completely, which is known as a tire blowout. When a tire loses its tread or blows out, the vehicle will become very difficult to control, especially at highway speeds. The loss of control frequently results in the vehicle changing direction suddenly and swinging around sideways, i.e., perpendicular, to the direction it was traveling. The sideways motion of the vehicle can cause the rim of the tire to dig into the road causing a serious rollover accident.

Rollover accidents also frequently occur when the vehicle encounters a drastic change in surface texture, such as going from pavement to grass or dirt, while in the sideways motion. In those circumstances, the change in surface will basically trip the vehicle and propel it into a roll.

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Tire detreading can result from myriad different manufacturing and design failures. Examples of such defects include improper design and placement of the belts and overlying tread, failure to include a nylon overlay or safety belt system, and poor adhesion of the tire components. In general, poor adhesion between the metal components of the tire and the rubber tread is the leading cause of tread separation.

Adhesion failures can result from several different design or manufacturing problems, such as the use of old or expired adhesives, unclean facilities, improper temperatures, incorrect chemical mixtures and the introduction of contaminants such as moisture, grease, foreign materials (e.g., gum wrappers, cigarette butts, etc.), rust and oxidation. The risk of tire detreading also tends to increase in warmer weather and at higher speeds, which can compromise the adhesive used to bind the tire together.

Due to the difficulty of getting rubber to properly adhere to metal, tire detreading is a problem mostly associated with steel-belted radial tires. Tire manufacturers can greatly reduce the risk of tread separation by including a nylon overlay system into the tire design. As discussed above, this system involves placing a nylon cap, sometimes referred to as a “safety belt,” between the steel belts and the outside tire tread. The nylon cap helps stabilize the steel belts and allows for greater adhesion between the tread and inner core of the tire.

As previously stated, this system is widely used in high-end American tires and in most tires made for sale in Europe. Including this important safety feature into the design of a tire would result in only marginal cost increases to the manufacturer, and there is no legitimate reason for their omission. Unfortunately, current auto safety standards do not mandate the use of a nylon overlay system. As such, many manufacturers will continue producing unsafe products in order to avoid the decidedly modest increase in production costs.