The vehicle pull problem is very important to driving safety. Major factors that may cause the pull problem related to tire include variations of geometric dimension (e.g. RPK) and stiffness (e.g. cornering stiffness, aligning stiffness), plysteer and conicity. In previous research, the influencing mechanism of these factors was well studied. But in fact, vehicle pull problem caused by tire is probabilistic. When we assemble four tires onto the car, there could be 384 different assembly arrangements. If there are significant differences among these four tires, there will also be significant differences in the influence of different tire assembly schemes on vehicle pull, which has not been systematically discussed in previous studies.
If we want to evaluate the pull performance of all these arrangements by vehicle test, it will be a time consuming process which will take almost 24 working days, along with a high test expense. Therefore, it is very necessary to develop an assistance simulation tool that can evaluate the effect of tire characteristics on vehicle pull problem efficiently.
In this study, a set of fast evaluation method is proposed for studying the influence of tire on vehicle pull problem and a relevant assistance tool is also developed based on CarSim software. With this tool, users can quickly calculate all possible vehicle lateral deviations when four tires are assembled onto the vehicle randomly and decompose the contribution of cornering stiffness, self-aligning stiffness, plysteer and conicity to the vehicle pull, as well as investigate the improvement on the pull problem after we make the direction of conicity of tires mounted on the same axle to be opposite. From the simulation and test results of this study, it can be found that the tire assembly scheme is very important for the evaluation of vehicle pull, especially when there are significant differences in the characteristics of tires assembled. These differences include not only the difference of plysteer and conicity, but also the difference of cornering stiffness and self-aligning stiffness.