In a turn, the sprung mass of the vehicle's body rotates around an axis known as the roll center. If the vertical distance between the roll center and the center of gravity is not zero, a torque (roll moment) equal to the centrifugal force times the distance between the center of gravity and the roll center will be exerted on the sprung mass, causing the body to lean towards the outside of the turn. This force is called roll couple. The effect of roll couple is positive camber of the wheels on the outside of the turn, which reduces their cornering grip. [my note: this applies both to the torsion-beam rear suspension on our cars and to independent suspension setups]

Roll couple is resisted by the suspension's roll stiffness, which is a function of the spring rate of the vehicle's springs and of the anti-roll bars, if any. The use of anti-roll bars allows designers to reduce roll couple without making the suspension's springs stiffer in the vertical plane, which allows improved body control without compromising ride quality, at least on smooth roads.

Increasing the roll stiffness of the suspension increases the rate of weight transfer to the wheels on the outside of the turn. As more weight is applied to the outer wheels, the adhesion of the tires is increased until their limits are reached, increasing their slip angles. If the front and rear weight transfer is unequal, the slip angles of the end with the greater weight transfer will be larger, resulting in understeer or oversteer. The use of anti-roll bars allows the weight transfer of the front and rear wheels to be adjusted separately, compensating for unequal front/rear weight balance and "tuning" the vehicle's handling characteristics.