Sway Bar Problems

by WilliamHanz

Sway bars are torsion springs used to resist body roll movements. They consist of a U-shaped tube steel connected to the body at two points, the left and the right faces of the suspension. In an automobile, when the left and right wheels begin to move at the same time, the sway bar rotates and doesn't bend. If the wheels move to a different direction, the bar then begins to twist.


Sway bars are used to perform two functions. The first is to reduce the body's tendency to lean due to the total roll stiffness of the automobile. The vehicle's roll stiffness affects the body lean, but doesn't affect the weight transfer from the inside to the outside wheels. The other function of sway bars is to regulate the handling balance of the vehicle. Understeering or oversteering behaviors cause the automobile to tune out as the proportion of the roll stiffness in the front also changes the reaction of the front and rear axles. In turn, this will cause the outer front wheel to run at either a higher or lower slip angle. Sway bars keep this event under control.


Since sway bars connect the wheels on the both sides of the automobile together, they tend to transmit one-wheel bumps toward the opposite wheel. Sway bars can cause jarring, waddling motions and increase the roll stiffness when the vehicle is driven on rough pavements. Because of this, the bars can cause the inside wheels to lift off when the car changes its direction. Other problems that involve sway bars include intermittent clunking effects, and rattle vibration at the front end of the vehicle, especially when it is driven on uneven surfaces.


When these problems are left unattended, the vehicle may continue to experience continuous clunking and jarring, since the front and rear wheels are no longer balanced. In the long run, it becomes difficult to steer the vehicle and may soon require tuneup, and eventually a system overhaul.


Problems involving sway bars can be resolved by repositioning the sway bar back at the center of the front wheel axle, in case the bar got misplaced due to aggressive steering. Sway bar replacement can be quite difficult as it can change the car's suspension control and total load capacity, so it is imperative that the vehicle's suspension is evaluated to maintain its overall balance.


Maintaining a properly aligned sway bar provides enhanced driving comfort, as well as smoother steering, especially on rough terrains. Since the sway bar keeps the vehicle stiff and balanced, the wheels are kept evenly aligned, even when the car changes directions aggressively.

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