Anti-Roll Bars (also called Torsion Bars or Sway Bars) are components in the suspension system which are connected to either the two front wheels or the two rear wheels (usually both sets), and pivot on a connection point on the chassis. The angled ends of the bar are connected to the active end of the suspension (the end that moves with the tires) and the overall effect of this is that the two wheels connected by a sway bar will move in unison with ease, but for one wheel to move independently, it will have to twist the sway bar, in addition to the force required to compress the spring and shock absorber.
Performance Anti-Roll Bars
Most production cars come with moderately weak anti-roll bars for two reasons: Manufacturers assume most drivers won't be taking corners quickly, and the vehicle can only go around a corner so quickly with a given tire. Because of this, many racers and enthusiasts buy thicker aftermarket sway bars to replace the originals.