You're probably pretty familiar with "grab handles." No, not the ones on the waists of middle-aged adults, but those mounted on the interior ceiling areas just above the passenger doors on many cars. These handles, when used properly, tend to prevent any undue familiarity between accompanying passengers during your hard-cornering maneuvers. As you likely know from "hands-on" experience, muscular and skeletal resistance applied through such handles can restrain your body's movement.
Anti-Roll.
Well, the sway bar-sometimes referred to as the "anti-roll bar"-operates on similar principles, keeping the body of a vehicle from leaning excessively while cornering. The effects of inertia and centrifugal force are thereby reduced through applied mechanical resistance.
This is accomplished, in practice, by employing a spring steel bar mounted transversely underneath your vehicle. A sway bar attaches both to the chassis and suspension lower control arms on each side via brackets, links and bushings. When cornering, the body will tend to roll away from the direction of the corner, compressing the outside suspension of the vehicle and unloading the inside. The sway bar is installed so that these forces are connected and work against each other. The unloading action of the inside suspension fights the loading action on the outside suspension, and vice versa, thus reducing the amount of body roll. Simple and effective, right?
Control Role.
Body roll needs to be controlled for reasons of vehicle safety, as well as for passenger comfort. When left unchecked, body roll reduces the efficiency of the tires on the inside of the corner, overloading the ones on the outside, and ultimately reducing the amount of road holding friction available.
Excessive roll will also change the relationship of the steering and suspension components to each other and to the road, often creating its own "steering effect" in the process. The net effect is that the vehicle will be less controllable, requiring immediate corrective action from the driver, lessening the driving experience for all concerned (at the very least).
Years ago, many passenger vehicles did not come with sway bars as standard equipment. Today, few cars come without them on their base models. Many are equipped with bars on both the front and rear, with larger bars often included in "sport" or "heavy-duty" suspension options.
Maintenance.
Maintenance on sway bar systems is generally easy to perform as there are few moving parts. Essentially, the system consists of the bar itself (usually round, sometimes hollow), body brackets and bushings (usually two: one left, one right) that are generally made of some kind of hard rubber, and links on each end connecting the bar to the control arm. Sometimes the link connections employ hard rubber bushings, and sometimes ball and socket connectors are used. The ball and socket (often called a "Heim joint") method usually is superior, offering a more direct connection and increased longevity.
The rubber end link bushings are usually the first to fail. After so much pushing and pulling they will finally tear, and completely disintegrate. When this occurs, lots of really obnoxious noises will begin, either a clatter when driving in a straight line over bumpy, patched or potholed roads, or creaking when cornering or entering driveways.
Replacements.
The repair is straightforward, unless inspection reveals chassis or suspension damage, or the bar itself is damaged. Usually complete end link kits are available either from the automaker (dealer) or through quality aftermarket sources. These kits include both the bushings and attaching link, sometimes for repair of both sides.
Just follow the safety and repair instructions outlined in the service manual or included instructions, keeping in mind that it is much easier to install the kits together as opposed to doing them one side at a time. The reason for this is that you'll be fighting against the normal function of the sway bar if you try the one-at-a-time approach.
The chassis bushings are generally easy to replace. Sometimes the old bushings are not slotted, so you'll have to slot them (by cutting) in order to remove them from the bar. Take care not to scratch the bar. The replacements are almost always slotted, so installation should be fairly easy.
If there are a number of bar size options for your vehicle, you'll have to carefully measure the diameter of the bar (a vernier is ideal for this) in order to get the right size bushing. Getting the wrong size will cause all sorts of problems, such as excessive noise, lateral bar movement, and premature bushing failure.
Now, with your sway bar system fully operational, you and your crew are ready to rock once again-but without the unwanted roll!
