Radial tires offer many advantages over bias ply tires, and steel was recognized early on as having desirable properties for the construction of radial tires belts. However, mating steel structures to the rubber structures in a tire is an engineering challenge and one of the principle difficulties in making safe and durable radial tires.
The steel/rubber interface is exposed in service to adverse mechanical, thermal, and chemical stresses which include combinations of static and cyclic (fatigue) stresses, as well as potential invasion of the structure by cuts and puncturing objects, moist air, and electrolytes such as sodium chloride. Deterioration of the composite structure takes place both during the heat exposure involved in curing the tire during manufacture and in the course of the tire wear during service. Foreseeable forms of misuse can enhance these stresses. Thus, the bonding process between steel and rubber is both critical and problematic.
In practice, these inherent stresses, environmental factors and manufacturing anomalies can conspire to cause a given tire to sustain a sudden separation of the tire's tread from its carcass with potentially catastrophic consequences. Typically such separations begin at the belt edge which serves as a form of stress concentrator. Design is crucial to preventing such incidents. Various design techniques, such as "safety belts" and or "strips", have been developed that will prevent such separations under normal circumstances.
Unfortunately, not all tires utilize the available design concepts, yet all are subject to the same stresses. The results of such a separation can be catastrophic accidents. Tires that do not employ adequate design strategies to avoid these failures are placing passengers and others at unnecessary risk and are unreasonably dangerous for their intended use.
James Bruce McMath is a member of the firm McMath Woods PA., in Little Rock, Arkansas.
Tire Wheel Separation Accidents / Tire Mounting Machine Defects
