Analysis of Causes of an Unintended Rollover During a Tread Separation Event Test CRASH Conference, Athens, Greece, July 4-6, 2006 Arndt, Mark W., Rosenfield, Michael J., Arndt, Stephen M., and Stevens, Donald C.

A high speed multiple rollover crash occurred during a test program designed to evaluate the disturbances to a vehicle’s straight ahead steady state path caused by a rear tire tread separation event. The tread separation that induced the crash was a partial tread separation event. The test run resulting in the rollover is documented by on-board test instrumentation and standard post-test crash investigation methods. Testing reported in previous papers documents a distribution of forces that cause an external disturbance to vehicles during tread separation events. These papers also document changes to vehicle steering characteristics following tread separation events. By themselves reported tread separation induced forces are insufficient to cause the initial vehicle motion in the rollover crash. Testing presented in this paper documents a change to vehicle handling stability due to tread separation induced rear wheel hop. Rear wheel hop and a special hop condition called tramp resulted in oversteer causing the vehicle to make an unintentional rapid turn. Characteristics of tread separation induced rear axle hop and tramp, including changes in vehicle handling, physical evidence left on the road, and the effects on vehicle motions are presented.

Measurement of Changes to Vehicle Handling Due to Tread-Separation-Inducted Axle Tramp, Society of Automotive Engineers, Inc., Paper No. 2006-01-1680, International SAE 2006 World Congress, Detroit, Michigan, April 3-6, 2006. Arndt, Mark W., Rosenfield, Michael J., and Arndt, Stephen M.

Tests were conducted to evaluate the effects of the tire-induced vibration caused by a tread-separating rear tire on the handling characteristics of a 1996 four-door, two-wheel-drive Ford Explorer. The first test series consisted of a laboratory test utilizing a 36-inch-diameter, single-roller dynamometer driven by the rear wheels of the Explorer. The right rear tire was modified to generate the vibration disturbance that results from a separating tire. This was accomplished by vulcanizing sections of retread to the prepared surface of the tire. Either one or two tread sections covering 1/8, 1/4, or 1/2 of the circumference of the tire were evaluated. The results demonstrated that a tire modified with two bonded-on tread sections driven at half speed replicated axle tramp characteristics of a modified tire with a single bonded-on tread section at the peak axle tramp speed. A second test series consisted of low-speed vehicle handling tests with a right rear tire modified with two bonded-on tread sections. The on-road testing showed that the modified right rear tire caused axle tramp and associated vehicle skate at the peak axle tramp speed during quasi-steady state and dynamic maneuvers. A 1999 four-wheel-drive Ford F-250 truck was tested with a tire modified by cutting away 1/4 of the tread and outer belt at two locations. The modified tire was placed at the left front position and low-speed vehicle handling tests were conducted at the peak axle tramp speed. Test results show front-axle tramp induced an increase in steer gradient and significantly reduced turning capability.

Tests Documenting Vehicle Handling with a Temporary-Use Rear Tire and a Run-Flat Rear Tire, Society of Automotive Engineers, Inc., Paper No. 2006-01-0905, International SAE 2006 World Congress, Detroit, Michigan, April 3-6, 2006. Arndt, Mark W., and Arndt, Stephen M.

Temporary-use-only spare tires are common standard equipment on motor vehicles while run-flat tires are offered as standard equipment on some motor vehicles. This paper describes testing on a 1995 GMC Safari all-wheel-drive minivan with a rear Uniroyal Hideaway/Temporary-Use-Only tire and a 1997 Mercury Grand Marquis with a self-supporting, run-flat tire manufactured by Bridgestone. The testing included circle turn tests and 180\mD step steer tests at target speeds of either 30 or 35 miles per hour (low-speed, J-turn test). Control tests were conducted with standard normally inflated tires. Both the standard tires and run-flat tires were also tested in a modified condition involving the removal of the tread and outer steel belt, simulating a tire which has experienced a complete tread-belt separation. The principal conclusions of this work are that temporary-use-only tires have characteristics that do not degrade handling and response of a minivan and that the run-flat tires have characteristics that favorably influence the handling and response of a passenger car that has sustained a loss-of-pressure tire disablement.