The Effects of Front Suspension Parameters on Road Wheel Toe Dynamics

Front road wheel toe dynamics directly affects tire wear and steering wheel vibration, which in turn negatively impacts customer satisfaction. Though static toe can be preset in assembly plants, the front road wheels can vibrate around steering axes or kingpin axes due to tire mass unbalance and nonuniformity. The frequency of the vibration depends on the wheel size and vehicle speed, while the amplitude of the vibration is not only dictated by the tire forces, but also by suspension and steering parameters. This paper presents a study on the sensitivities of the front road wheel toe dynamics to the parameters of a short-long-arm suspension (SLA) and a parallelogram steering system. These parameters includes hard point shift, steering gear compliance, gear friction, control arm bushing rates, friction in control arm ball joints, and compliance in tie rod outboard joints. The simulations were performed using the multibody dynamics analysis package ADAMS, while the tests were conducted on a chassis roll. The simulation and test results are well correlated, showing the effects of the friction and compliance parameters on the toe angle amplitude. The study provides valuable information in developing design strategies for minimizing the toe vibration caused by the tire imperfection.