Roll Axis

The roll axis is a line drawn between the front and rear roll centers. This is the axis about which the suspended mass rotates about. This axis is often called the kinematics roll axis.

Roll Axis Height

A roll axis that is above the ground will;

·         Decrease roll

·         Increases jacking

·         Instant geometric transfer loads the outside tire and unloads the inside tire

·         Lower suspended mass inertia

·         Improves turn in

·         Increase ride height

A roll axis that is under the ground will;

·         Increase roll

·         Create anti jacking

·         Instant geometric transfer loads the inside tire and unloads the outside tire

·         Higher suspended mass inertia

·         Diminish turn in response and

·         Lower ride height

Roll Axis Inclination

The height of the front and rear roll centers will affect how the roll moment is distributed between the front and rear wheels. If the rear roll center is higher than the front there will be a larger roll moment on the rear tires this will lead to a larger geometric weight transfer on the rear axle that will cause the rear tires to become more unevenly loaded during a corner and hence have less lateral grip. Raising and lowering the front and rear roll centers will alter the understeer-oversteer characteristics of the car.

Roll Axis Lateral Movement

As the suspension rolls the roll axis will move lateral. How much it moves will depend on the suspension geometry. The Roll axis can skew because of different front and rear suspension geometry and roll angles.

A roll center that is closer to one side of the car and inside the track, is like having a stiffer springs on that side of the car and a softer spring on the other side.