Steering Knuckle

The steering knuckle (sometimes called a spindle or upright) is a heavy-duty structural hub that connects a vehicle's wheel to its suspension and steering systems. Bolted to the suspension control arms (via ball joints) or the strut assembly, the steering knuckle serves as the mounting foundation for the wheel hub assembly, brake calipers, and steering tie rods. It is the part that physically pivots to turn the front wheels.

Steering knuckles are typically manufactured from cast iron or forged aluminum to handle the massive forces of steering, braking, and carrying the vehicle's weight. On steering wheels, the knuckle features a steering arm that connects to the outer tie rod end. When the steering rack pushes or pulls the tie rod, the knuckle pivots, turning the wheel.

Steering knuckles are extremely durable and rarely wear out from normal driving. However, they can bend or crack due to physical impacts, such as hitting a deep pothole, striking a curb, or being involved in a collision. A bent steering knuckle will throw off the wheel alignment, causing steering pull, tire wear, and handling problems that cannot be adjusted out during a standard alignment.

If a steering knuckle is bent or cracked, it must be replaced. During replacement, the wheel hub, wheel bearing, and brake components are transferred to the new knuckle, and a wheel alignment is performed to restore handling parameters.