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Recently, papers have been published purporting to study the effect of rear axle tramp during tread separation events, and its effect on vehicle handling [1, 2]. Based on analysis and physical testing, one paper [1] has put forth a mathematical model which the authors claim allows vehicle designers to select shock damping values during the development process of a vehicle in order to assure that a vehicle will not experience axle tramp during tread separations. In the course of their work, “lumpy” tires (tires with rubber blocks adhered to the tire's tread) were employed to excite the axle tramp resonance, even though this method has been shown not to duplicate the physical mechanisms behind an actual tread belt separation. This paper evaluates the theories postulated in [1] by first analyzing the equations behind the mathematical model presented. The model is then tested to see if it agrees with observed physical testing.

In repeated physical testing of vehicles at or near their handling limit, tire shoulder wear occurs that is not typical of normal customer use. It has been observed for decades that this type of severe cornering induced tire wear can have a significant effect on the force and moment characteristics of tires. In this study, the severe cornering wear effect was studied by testing vehicles in a highly controlled manner using a robot steering controller. This testing shows how vehicle response to the exact same steering input changes significantly as the number of runs on the same tires accumulates. In fact, vehicles were found to not lift tires from the ground in initial runs then tip-up hard onto outriggers in later runs as the tires are abraded. Additionally, for one vehicle configuration an additional run was made with tires that had accumulated 16,000 km (10,000 miles) of normal customer usage.

There has been very little investigation into the area of tire aging and whether storing a tire will change it's properties, in particular ‘limit’ or ‘saturated’ properties, over time. In order to study how the performance characteristics of tires change when the tires are stored, a series of force and moment tests were performed on five modern day radial tires of different make, brand, type, and size. The tires were all purchased at the same time for a given tire set and had the same DOT code. Near the date of purchase, some of the tires were tested on the Veridian TIRF (Tire Research Facility) machine in order to measure their force and moment characteristics. Other tires of the lot were placed on a tire rack in a storage building. Years later, these tires were sent to the same test facility and were measured under the same test conditions. The data indicates that tire performance characteristics change very little with time.

The concept of vehicle understeer and oversteer has been well studied and equations, test methods, and test results have been published for many decades. This concept has a specific definition in the steady-state driving range as opposed to quantification in highly transient limit handling events. There have been specific test procedures developed and employed by automotive engineers for decades on how to quantify understeer. These include the constant radius method, the constant steering wheel angle/variable speed method, the constant speed/ variable radius method, and the constant speed/variable steer method. These methods are very good for calculating the understeer gradient but care must be taken in interpreting the result at the limits of tire traction since lateral tire forces can be reduced on a drive axle when significant throttle is applied.

In this study, tests were performed on four different vehicles, each equipped with a version of electronic stability control (“ESC”). Tests were performed on a 2000 four door sedan, a 2002 four door sedan, a 2002 five door hatchback, and a 2003 large rear wheel drive sport utility vehicle. This selection allowed for the evaluation of different ESC systems and strategies on their ability to accommodate a separated rear tire. The steer inputs were applied to the vehicles manually by test drivers and were purposely selected to generate displacements so that the ESC systems would activate. The results of this study demonstrate that ESC systems can be overwhelmed by some steering demands when a rear tire has lost its tread. This fact does not constitute a problem with the ESC systems or the vehicles tested. It merely confirms that ESC systems will not always keep a vehicle from sliding or spinning out when a tire is disabled.

There have been many articles published in the last decade or so concerning the components of an electronic stability control (ESC) system, as well as numerous statistical studies that attempt to predict the effectiveness of such systems relative to crash involvement. The literature however is free from papers that discuss how engineers might develop such systems in order to achieve desired steering, handling, and stability performance. This task is complicated by the fact that stability control systems are very complex and their designs and what they can do have changed considerably over the years. These systems also differ from manufacturer to manufacturer and from vehicle to vehicle in a given maker of automobiles. In terms of ESC hardware, differences can include all the components as well as the addition or absence of roll rate sensors or active steering gears to name a few.

There has been a general consensus in the scientific literature that a rim gouging, not scraping, into a roadway surface generates very high forces which can cause a vehicle to overturn in some situations. However, a paper published in 2004 attempts to minimize the forces created during wheel rim gouging and the effect on vehicle rollover. This paper relied largely on heavily filtered lateral acceleration data and discounted additional test runs by the authors and NHTSA that did not support the supposed conclusions. This paper will discuss the effect of rim gouging using accepted scientific methods, including full vehicle testing where vehicle accelerations were measured during actual rim gouging events and static testing of side forces exerted by wheels mounted on a moving test fixture. The data analyzed in this paper clearly shows that forces created by rim gouges on pavement can be thousands of Newtons and can contribute to vehicle rollover.

In this study, tests were performed with modified tires on twenty-two different vehicles to measure their steering and handling capacities with a fully separated tire. Vehicles were tested with delaminated tires (i.e. tires where the tread and upper steel belt were removed) placed on the front suspension as well as the rear. These tests were performed using open loop steering evaluations at highway speeds and according to the Society of Automotive Engineers procedure J266, which includes testing to measure the steering required to follow a circular path at ever increasing speeds until the limits of tire traction are exceeded. The SAE J266 one hundred foot circle test was performed with both good tires and with a front or rear tire that had a totally separated tread and upper belt. In the tests with good tires, the vehicles could achieve a maximum lateral acceleration in the range of 0.65 g to in excess of 0.80 g in both clockwise and counterclockwise directions.

There have been several recent articles published concerning the effect of a tire tread separation on vehicle handling, but lately the literature has been silent on the situation where a tire airs out. This paper studies how various vehicles steer and handle during and after a tire deflates while the vehicle is traveling at speed. Utility vehicles, pickup trucks, and vans were tested by deflating front and rear tires. The air out condition was created by using a special test device that fired a twelve gauge shotgun shell at the sidewall of a tire while the vehicle was traveling at freeway speeds. The vehicles were instrumented with on board video equipment and a computer with transducers to measure both driver inputs and vehicle responses during the testing. The results show that a rapid tire air out creates a slight pull to the side of the deflated tire which then requires a small corrective steer to maintain a straight ahead course.

In this study, tests were performed on eight different vehicles, each equipped with a version of electronic stability control (“ESC”). Tests performed on a dry test surface included a 1999 two door sports car, a 2000 four door sedan, a 2002 four door sedan, a 2003 large rear wheel drive sport utility vehicle, and a 2002 five door hatchback. Tests performed on a wet surface were isolated to a full size rear wheel drive sport utility vehicle. Tests performed on a snow and ice covered surface included a 2003 mid size sport utility vehicle, a 2002 full size sport utility truck, and a 2007 mid size sport utility vehicle; all from different manufacturers. This selection allowed for the evaluation of different ESC systems and strategies on various surfaces to violent steering demands. The steer inputs were applied to the vehicles manually by test drivers and were purposely selected to generate large displacements so that the ESC systems would activate.

In this study, tests were performed with modified tires at the various front and rear positions on seventeen different vehicles to determine the effect of a full tire tread belt separation on a vehicle at highway speeds. The driver's steering and braking inputs were measured along with the vehicle responses during the event. The results show that the forces of a full tread belt separation generally do not force a vehicle out of a driver's control and that only small steering corrections are required to remain in the original lane of travel during the tread belt separation event. Additionally, forces due to the separating tires do not result in violent hop or tramp suspension responses during the separation event.

One important part of the vehicle design process is suspension design and tuning. This is typically performed by design engineers, experienced expert evaluators, and assistance from vehicle dynamics engineers and their computer simulation tools. Automotive suspensions have two primary functions: passenger and cargo isolation and vehicle control. Suspension design, kinematics, compliance, and damping, play a key role in those primary functions and impact a vehicles ride, handling, steering, and braking dynamics. The development and tuning of a vehicle kinematics, compliance, and damping characteristic is done by expert evaluators who perform a variety of on road evaluations under different loading configurations and on a variety of road surfaces. This “tuning” is done with a focus on meeting certain target characteristics for ride, handling, and steering One part of this process is the development and tuning of the damping characteristics of the shock absorbers.