In 1934 M. Olley suggested, in his paper “Independent Wheel Suspensions - Its Whys and Wherefores”, that a rear axle stiffness slightly higher than proportional to rear axle load would give improved comfort.
By the introduction of body fixed coordinates a velocity dependent damping factor occurs in the equations of motions. That factor has been named inertial damping.
The linear study of the parameter space shows that a stiff front suspension will cause a separation of the damping of the body eigenfrequenciesat increased vehicle velocity. On the other hand, and this was the conclusion of Olley, a soft front suspension will cause a separation of the frequencies at increased velocity.
As the system dampings and the natural frequencies in most cases vary with the velocity of the vehicle the stability margin should be checked.
The theoretical results indicate that good ride forwards can cause bad ride during reverse driving.
The non-linear study indicates that the linear study is conservative regarding the critical velocity.
Introduction of the momentum of the vehicle in the dynamic analysis will deepen the understanding of vehicle dynamics and improve future suspensions.