ON waves of one wheel base and shorter, especially at high speeds, the author says that the action of unsprung masses is important for riding comfort, it determines what we usually call harshness and shake in a car.
A study of this problem has led him to the following conclusions:
Unsprung masses greatly reduce harshness, but they amplify wheelhop and make suspension shakes possible. These bad effects must be overcome by the choice of suspension geometry and stiffnesses. A general understanding of suspension shakes exists and is helpful in overcoming them, but trial-and-error methods on a given car will always be necessary to find the best balance of the many factors involved.