When formulated and designed correctly, polyurethane bushings will be the last bushings you put on the vehicle. Rubber deterioration also compounds the original vacillation of the suspension. This works to a certain degree when the rubber is new. As it starts to age, the ability to rebound back to the original shape diminishes. This translates to steering deflection.
Deflection causes changes in camber, caster, and toe angles, influencing steering control.
Another shortcoming of rubber is its displacement under load. The result is vague handling. When a vehicle initiates a turn, the load placed on the suspension components is considerable. In fact, deflection of the rubber requires some of the bushings do the job of the suspension components they adjoin. Performance polyurethane bushings do not crush like rubber.