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Tire failures, including tread belt detachments, have been associated with loss of control crashes including rollovers. Numerous reasons exist for control loss including forces created by the failed or failing tire, cornering capacity diminishment for the detreaded tire combined with control demands beyond the remaining capacity of the vehicle and inappropriate driver demands including excessive steering. Extensive studies have been completed to define the various causes of control loss and to identify risk-reducing countermeasures. These studies have included reconstructions of crashes and tests of real vehicles in test track environments with tires purposely caused to fail.

Understanding and measuring a vehicle's response to cyclical vertical inputs is fundamental to evaluating suspension tuning and handling characteristics. By using a frequency sweep with in-phase and out-of-phase decreasing displacements to the tires, the vehicle sprung and unsprung mass responses can be measured to quantify vertical accelerations across a frequency range. With these data, the resonant frequency characteristics of the front and rear suspensions can be determined. In addition, the acceleration gains of the unsprung mass and the vehicle body can be calculated. This evaluation is effective in identifying the similarities and differences in suspension response among various vehicles and in quantifying the changes of the response to various types of suspension tuning.

In this study, tests were performed to understand the effects of asymmetric longitudinal forces on vehicle response which may be created in certain staged partial tire tread belt detachment tests. In a very small number of tests performed by others, tires cut to simulate partial tire tread belt detachments created longitudinal drag forces at the separating tire that induced substantial vehicle yaw. This drag force and yaw response are independent of vehicle type and suspension type; they are created by the separating tire tread interacting with the road surface and / or vehicle. Similar yaw inducing drag forces are further demonstrated by applying braking to only the right rear wheel location of an instrumented test vehicle. It is shown that vehicle yaw response results from this longitudinal force as opposed to vertical axle motion.

Designers of motor vehicles must consider driver and environmental factors to assure that vehicle capacities will be compatible with the likely demands of both to achieve a reasonable degree of safety. Extensive related data are available as a result of a large scale study performed by The National Highway Traffic Safety Administration entitled “Light Vehicle Antilock Brake Systems Research Program”. Mazzae, et al [1] have published a report that described the nature of the program and its general results. Large bodies of data were created that provide further insight into motor vehicle driver behavior in crash avoidance situations. The data quantify driver behaviors in the use of steering and braking controls and of the test vehicle response to these control demands. The current work provides an analysis of these data for consideration by motor vehicle designers and others.

The causes, conditions and circumstances of axle shaft failures are analyzed for use in reconstructing a variety of crashes. A literature search was performed to determine the frequency and the role of vehicle defects, such as axle shaft failures, to crash causation. Real world case studies of axle shaft failures are presented. Static testing force levels required to fracture axle shafts are compared to lateral forces encountered under normal and crash avoidance driving conditions. Vehicle and roadway physical evidence is presented when axle shafts are caused to “fracture” under dynamic testing. Results of the dynamic testing are compared to real world case studies.