Two Guys Rally

Anti-Roll Bars
[ August 5th, 2008 ] By: Charles Smith Posted in » Ramblings

Without an anti-roll bar, when a car turns left the inertia of the car would cause the right side suspension to compress and the left side suspension to extend. This is primarily due to the center of gravity (CG) being above the axis about which the suspension rotates. A higher CG means a larger tendency to roll, as many of you have probably experienced with driving different sized cars. A roll bar keeps the suspensions at similar compressions/extensions and that makes the car body roll less in corners. It is a pretty simple concept.

However with any simple concept there are many implementations of it in the real world. Sway bars, another name for the anti-roll bar, connect the left wheel to the right wheel (front with front and rear with rear). Most of them tend to be torsional springs (springs that are designed to resist twisting rather than compression) but there is at least one electronic method.

The trick to the adjusting the bar is to allow for the “correct” amount of roll to keep the tires on ground. If you go too stiff and corner real hard, you will end up lifting a wheel off of the ground (inside front or rear, depending on if you’re accelerating or braking). If you go too soft (ie none) the car will have grip, but the car’s response will feel sluggish. In Rally it comes down to a combination of overall suspension stiffness, driver preference and style with a mixture of stage terrain requirements. While there is some science behind suspensions, a lot of it is just finding a setup that inspires confidence in it’s handling.

A final note: I have noticed many individuals refer to a strut tower brace as a sway bar. That is just plain wrong, hopefully this video can show you how a strut tower brace would not be a sway bar.