Purpose of the Stabilizer Bar, Links, & Bushings
When making a turn while driving your car, you may have noticed that your body tends to move toward the outside of the turn. The same thing happens to all the parts of your vehicle during a turn. Additionally, the parts of the vehicle on the outside of the turn get pushed down toward the road, and the parts of the vehicle on the inside of the turn lift up and away from the road. If you take a turn fast enough, the tires on the inside of the turn could actually lift off the road and the vehicle could flip over.
Body roll occurs when more weight is placed on the outside tires and less weight is placed on the inside tires, which in turn reduces traction and vehicle control. Ideally, the body of the vehicle will remain flat throughout a turn so the weight stays evenly distributed on all four tires. An even more ideal scenario would be a fine-tuned vehicle suspension that would reduce body roll, keep the vehicle flat, and not impair the independent movement of each tire.
A stabilizer bar system is part of most vehicle suspension systems. It is designed to reduce body roll and fine tune the suspension as mentioned in the ideal scenario above. It connects the front wheels (left and right), and in many cases the rear wheels, through short links connected to a suspension component at each wheel. Stabilizer bars are also referred to as anti-sway bars, sway bars, anti-roll bars, and roll bars.
Stabilizer bar systems consist of several components including the stabilizer bar itself, stabilizer links, stabilizer link bushings or sockets, stabilizer bar to vehicle frame bushings, and bushing brackets to hold the bushings in place against the frame or unibody member. All of these components are designed to help force opposing sides of the vehicle to lower or rise to similar heights and reduce the body roll of the vehicle on curves, sharp corners, or over large bumps.
A stabilizer bar is intended to keep the vehicle's body flat by moving force from one side of the body to the opposite side. To understand how a stabilizer bar works, picture a metal rod constructed out of tubular steel that is one to two inches in diameter and in a "U" shape. If your front tires are five feet apart, the rod will be approximately four feet long and sit between the two tires. The rod is securely attached to the frame or unibody member of the vehicle in two locations. Bushings and brackets are used to allow the rod to flex and rotate, but stay in position where it is attached to the vehicle frame. Links, or arms, are used to attach the ends of the rod to the suspension component, typically the lower control arm or other component that holds the wheel, on both sides. The links have bushings or ball socket type joints to allow more flex and controlled movement.
When your vehicle begins to turn, the suspension component at the outside of the turn gets pushed downward. The link attached to the stabilizer bar also gets pushed downward, and applies torsion, or a twisting motion, to the "U" shaped rod. The torsion then moves the link at the other end of the rod, causing the suspension on the other side of the car to react as well. This causes the vehicle's body to stay flatter in the turn as the suspension at the outside of the turn is forced to rise, and the suspension at the inside of the turn is forced to lower, thus stabilizing the height distribution during the turn.
If your vehicle does not have a stabilizer bar, it will likely have trouble with body roll when turning. If you have too much stabilization from the stabilizer bar, your vehicle will lose independence between the suspension members on opposing sides of the vehicle. The stabilizer bar also affects ride comfort by distributing the effects of bumps in the road to both sides of the vehicle.Stabilizer bar links are typically attached to the lower control arm. Steering and handling can be negatively impacted when they begin to wear. Most of the time, the actual culprit is the rubber bushings or the ball socket joints that are designed to take most of the impact and help protect the metal parts from wearing.
Squeaks can result when the stabilizer bar to frame bushings have had water intrusion, causing rust to develop on the bushings and on the metal rod where the bushings contact. Bushings can also harden, crack, and dry out, which will also result in squeaks. These squeaks will be noticeable when going over bumps, turning, or anytime the bar experiences torsion and rotates in the bushings.
When stabilizer bar components begin to wear, the symptoms can range from barely noticeable to significant. Stabilizer bar links should fit snugly, without any play or movement except between rubber bushings, or the controlled movement of the ball socket joint. When the links are worn, the stabilizer bar will begin to make rattling and clunking sounds, especially when you drive around corners or over bumps. Common signs of faulty stabilizer bar components include rattling or clunking noises from the tire area, poor handling, excessive body roll, squeaking, and a loose or sloppy steering feel.
Stabilizer bar components should be visually inspected, and should also be listened to while the vehicle is being driven. The stabilizer bar should be inspected for damage and cracks. The stabilizer bar to frame bushings should be inspected to make sure they are present, tight, and show no signs of cracking, degrading, or rust and oil contamination. The stabilizer links should also be inspected for damage, cracking, or degraded bushings. Bushings and ball socket joints should be inspected to ensure they are snug. Have an ASE certified technician test drive your vehicle and visually inspect your stabilizer bar system at least annually.