left and right wheels move together, the bar rotates about its mounting points. If the wheels move relative to each other, the bar is subjected to torsion and forced to twist. Each end of the bar is connected to an end link through a flexible joint. The anti-roll bar end link connects in turn to a spot near a wheel or axle, transferring forces from a heavily loaded axle to the opposite side. Forces are therefore transferred: from the heavily loaded axle to the connected end link via a bushing to the anti-sway (torsion) bar via a flexible joint to the connected end link on the opposite side of the vehicle to the opposite axle. The bar resists the torsion through its stiffness. The stiffness of an anti-roll bar is proportional to the stiffness of the material, the fourth power of its radius, and the inverse of the length of the lever arms (i.e., the shorter the lever arm, the stiffer the bar). Stiffness is also related to the geometry of the mounting points and the rigidity of the bar's mounting points. The stiffer the bar, the more force required to move the left and right wheels relative to each other. This increases the amount of force required to make the body roll. In a turn the sprung mass of the vehicle's body produces a lateral force at the centre of gravity (CG), proportional to lateral acceleration. Because the CG is usually not on the roll axis, the lateral force creates a moment about the roll axis that tends to roll the body. (The roll axis is a line that joins the front and rear roll centers). The moment is called the roll couple. Roll couple is resisted by the suspension 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 without making the suspension's springs stiffer in the vertical plane, which allows improved body control with less compromise of ride quality. One effect of body (frame) lean, for typical suspension geometry, is positive camber of the wheels on the outside of the turn and negative on the inside, which reduces their cornering grip (especially with cross ply tires). Main functions Anti-roll bars provide two main functions. The first function is the reduction of body lean. The reduction of