Rear Control Arm

The control arm of a vehicle is alternatively also known as the A-arm, it is basically a hinged suspension link present between the chassis and the suspension upright/hub that carries the wheel. The chassis (inboard) of a control arm is attached via a single pivot, which is usually a rubber bushing. This enables it to control the position of the outboard end in only a single degree of freedom, at the same time maintaining the radial distance from the inboard mount. Even though the it is not freely able to move the single bushing doesn't control the arm from moving back and forth, this motion is constrained by a separate link or radius rod. In the wishbone structure it is not the same; wishbones are triangular contain two widely spaced inboard bearings. These bearings restrict the outboard end of the wishbone from moving back and forth, hence controlling two degrees of freedom, and without requiring additional links. Majority of the control arms form the lower link of a suspension. In few designs they are used as the upper link, typically with a lower wishbone. The additional radius is attached to the upper arm.

The purpose of the control arm is to ensure the vehicle doesn’t experience too much movement when going over bumpy roads. The control arm connects the wheel hub and steering knuckle to the frame of the vehicle. The bushings of the control arm play an integral role in ensuring comfort and smooth handling during drive. They do this by acting as a cushion to the suspension system which then controls the noise, vibrations thereby providing a smoother, softer ride over bumps and even during sharp turns.

The control arm works in an highly mechanical manner. It is connected on one end via a ball joint to the steering knuckle which is attached to the wheel via a hub and bearing assembly. The other end is attached to the vehicle frame/body. Whenever the vehicle goes over the bump, the control arm starts it job by pivoting up and down with the wheel, and allowing the body of the vehicle to remain stable. On the frame/body side the control has one or a pair of bushings which enable it to pivot in this manner.

The control arm connects the wheel hub and steering knuckle to the frame of the vehicle. Equipped with bushings on the frame side of the vehicle, they also have a ball joint which is present on the wheel side of the vehicle. This helps in flex as well as controlled movement as per road conditions, and steering input from the driver.