Stabilisator

Subjects:

  • Stabilisator
  • strut bridge

Stabilizer:
A stabilizer bar is a solid steel bar in a U-shape that is mounted to the struts at the ends and to the body in the middle. The purpose of the stabilizer bar is to counteract the tendency of the car to roll when cornering. It will improve cornering stability by making the struts work together in the suspension. The anti-roll bar ensures roll stiffness of the front or rear axle.
When cornering, the springs on the inside of the vehicle will bounce and those on the outside will compress. When turning to the left, the springs on the left (inner bend) will spring out and the springs on the right (outer bend) will compress. The car now makes a roll movement. The rolling depends on the role center of the car. The location of the center of gravity and the roll center must be as optimal as possible; they should be as close together as possible. The further apart the center of gravity and roll center are, the more the vehicle will roll.

Because one side compresses and the other side springs out, the stabilizer bar will twist. The rod tries to keep the two sides equal and so will pull down the body on the side that is bouncing (the inside). Because this side is pulled down, it will also partially deflect. This achieves the purpose of the stabilizer bar; The movement from one wheel has been transferred to the other wheel. The car is now straighter and more stable in the bend, because it now leans much less. This greatly improves cornering stability.

The stabilizer bar is attached to the body with rubbers. At the ends of the stabilizer there are coupling rods on both sides that attach the stabilizer bar to the suspension strut or the wishbone. If there is space on the rubbers or on the balls of the coupling rods, a creaking or thumping noise will be heard when driving on a bumpy road.

The image above shows the complete front axle of a car. The stabilizer bar with the rubbers and the brackets are clearly visible. The purple brackets with rubbers shown are on the subframe and the two coupling rods shown in purple are attached to the wishbones. The stabilizer bar therefore pulls and pushes against these wishbones.

The stabilizer bar also has a lot of influence on the steering behaviour:

  • Front axle roll stiffer: more understeer (so less oversteer)
  • Rear axle roll stiffer: more oversteer (so less understeer)
    It is therefore important when increasing the roll stiffness, i.e. when adding or adjusting a stabilizer, to do the same for the front and rear axles. If only the front axle is made stiffer, the car is more likely to understeer. This means that the car will go straight ahead faster in a bend.

Strut bridge:
The functions of the stabilizer bar and the strut bridge are often confused. It is often thought that they have the same function, but this is not the case. However, a stabilizer bar has the function of improving cornering stability by transmitting the movements of the two wheels to each other. The purpose of a strut bridge is to prevent torsion in the body and chassis. A strut bridge is a rod that is mounted at the top between the ends of the 2 struts under the hood. Some cars also have a bridge under the front suspension.
When cornering, the body will also twist slightly. By means of the strut bridge, that twisting will be counteracted because the body is then stiffer, and this will also be noticeable during sporty driving. You can drive more sporty and faster through the bends. That is why you see many sports cars where the owner has mounted a strut bridge himself. Most sporty cars that are produced today already have a strut brace fitted as standard.

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