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Stabilizer:
A stabilizer bar is a solid steel bar in a U-shape mounted at the ends to the struts and in the middle to the chassis. The purpose of the stabilizer bar is to counteract the tendency of the car to roll when cornering. It improves cornering stability by making the struts in the suspension system work together. The stabilizer bar provides roll stiffness to the front or rear axle.
When cornering, the springs on the inside of the vehicle will extend, and those on the outside will compress. In a left turn, the springs on the left (inner) side will extend, and those on the right (outer) side will compress. The car now makes a rolling motion. The rolling depends on the car’s roll center. The location of the center of gravity and the roll center must be as optimal as possible; they should be as close to each other as possible. The further apart the center of gravity and the roll center are, the more the vehicle will roll.
As one side compresses and the other extends, the stabilizer bar will begin to twist. The bar tries to keep the two sides equal and will pull down the side of the chassis that is extending (the inside). Because this side is pulled down, it will also compress slightly. This achieves the stabilizer bar’s goal: transferring the movement of one wheel to the other. The car now lies flatter and more stable in the corner, reducing lean significantly. Thus, cornering stability is greatly improved.
The stabilizer bar is attached to the chassis with bushings. At each end of the stabilizer are links connecting the stabilizer bar to the strut or control arm. If there’s play in the bushings or on the ball joints of the links, a creaking or knocking sound will be heard when driving over a bumpy road.
The image above shows the complete front axle of a car. The stabilizer bar with the bushings and brackets is clearly visible. The purple brackets with bushings are attached to the subframe, and the purple links are attached to the control arms. Thus, the stabilizer bar pushes and pulls against these control arms.
The stabilizer bar also greatly influences handling:
- Stiffer front axle: more understeer (less oversteer)
- Stiffer rear axle: more oversteer (less understeer)
Therefore, when increasing roll stiffness, such as adding or modifying a stabilizer, it’s important to do this equally for both the front and rear axles. If only the front axle is made stiffer, the vehicle will tend to understeer more, meaning it will be more prone to going straight in a turn.
Strut Tower Brace:
The functions of the stabilizer bar and the strut tower brace are often confused. It’s often thought they serve the same function, but this is not the case. The function of a stabilizer bar is to improve cornering stability by transferring movements between the two wheels. A strut tower brace aims to counteract torsion in the chassis and bodywork. A strut tower brace is a bar mounted at the top between the ends of the two struts under the hood. Some cars also have a brace under the front suspension.
When cornering, the chassis will also experience a bit of torsion. Using the strut tower brace, torsion will be reduced because the body will be stiffer, noticeably improving sporty driving. This allows for more sporty and faster cornering. That’s why many sports cars have owner-installed strut tower braces. Most sporty cars produced today come standard with a strut tower brace.
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