Comparative Dynamic Analysis of Tire Tread Belt Detachments and Stepped Diameter (“Lumpy”) Tires

In this study, tests were performed with modified tires at the right rear location on a solid axle sport utility vehicle to compare vehicle inputs and responses from both: (1) staged tire tread belt detachments, and (2) stepped diameter (“lumpy”) tires. Lumpy tires consist of equal size sections of tread that are vulcanized at equidistant locations around the outer circumference of the tire casing. Some have used lumpy tires in attempt to model the force and displacement inputs created by a tire tread belt separation. Four configurations were evaluated for the lumpy tires: 1-Lump, 2-Lump (2 lengths), and 3-Lump. In addition to measuring vehicle accelerations and velocities, the forces and moments that transfer through the road wheel were measured at the right and left rear wheel locations using wheel force transducers; displacements were measured between the rear axle and the frame, ride height displacements were measured at the four corners of the vehicle, and accelerations were measured on the rear axle. The results show that the stepped diameter tires do not create inputs to the vehicle and responses from the vehicle similar to a tread belt detachment. In addition, the use of lumpy tires as surrogates for tread belt detachments to study the resulting vehicle responses was shown to be not valid. The forces created in the tire tread separation tests performed did not force the vehicle out of the drivers' control.