What Causes the Rear of the Car to Sway Left and Right When Driving Over Bumpy Roads?
2 Answers
The reason for the rear of the car swaying left and right when driving over bumpy roads is: wheel undulation (up-and-down bouncing) causes the wheels to deflect upward in an arc. This arcing motion changes the distance between the tie rods connected to the wheel knuckles and those connected to the vehicle (front tie rods are connected to the steering gear, while rear tie rods are connected to the chassis). The change in distance will cause the wheels to tilt inward or outward, thereby affecting the vehicle's steering. When the car sways slightly left and right while driving, this is primarily caused by the vehicle pulling to one side. There are many reasons for such pulling, including insufficient tire pressure, uneven tread wear, issues with the suspension system design, or damage, deformation, or misalignment of the suspension.
Last year when I drove my car over bumpy roads, the rear end shook violently. Upon inspection, I found that the rear shock absorber was leaking oil—that part is responsible for absorbing shocks, and when it fails, the car wobbles. Another possible cause could be uneven tire pressure or deformed rims; low pressure makes the tires uneven, causing them to sway back and forth when hitting potholes. Loose control arms or damaged ball joints in the suspension are also common culprits—if these linkages fail, the car body can't stay stable. If the car has been modified to lower its ride height, the altered suspension geometry can also worsen the wobbling. I think the first step should be to check the tire pressure and use a flashlight to inspect the shock absorbers for oil stains. If the wobbling is accompanied by strange noises, it's likely that the stabilizer bar clips are loose. Safety is crucial, especially at high speeds where severe wobbling can lead to loss of control. I recommend getting the suspension system checked at a repair shop as soon as possible—don't wait until you break down halfway like I did and regret it.
