A sway bar (also called an anti-sway bar or anti-roll bar) is an automobile suspension device. It connects opposite (left/right) wheels together and acts as a torsion spring to force the wheels to act together. When one wheel rises, the other must also rise somewhat. It is also attached to the body of the vehicle, reducing body roll in corners. When the body begins to roll, it acts on the sway bar to lift the outside wheel and exert pressure on the inside one.
The effect of these motions is reduced body lean in corners and improved traction. Sway bars must be carefully selected, however, since a too-heavy bar will affect the other chassis dynamics (causing oversteer or understeer) and can lead to a harsh ride.
