Cars Simplified: Everything Automotive Explained

Anti-Roll Bars

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 (via sway bar links) to the active end of the suspension (the end that moves with the tires, usually a control arm) 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. Having an anti-roll bar equipped isn't without a few drawbacks, however.

Positive Effects

Sway bars provide a more level cornering experience. Without a sway bar, the springs would have to be stronger to keep the vehicle just as level, which would lead to a harsher, less comfortable ride.

Negative Effects

The sway bar creates an equal amount of lifting force on both control arms; the difference in height between two tires is only due to the amount of twist in the torsion bar and bushings. A bump that would normally only be felt on one side is transferred in part to the other side as well.

On either end of an anti-roll bar is a link, connecting each end of the bar to the lower control arm. The links come in a number of different designs, but tend to have either bushings or ball joints on the ends to allow flexibility at the connection points.

Performance Anti-Roll Bars

A Performance Sway Bar

Most production cars come with moderately weak anti-roll bars for two reasons: Manufacturers assume most drivers won't be taking corners quickly on a regular basis, 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 original bars.

Indy Car Anti-Roll Bars

Eibach Anti-Roll Bars

How Anti-Roll Bars Work by Engineering Explained