Do you really know the steering knuckle?

What is a steering knuckle?

The steering knuckle is a component of the front suspension on a vehicle. The steering knuckle houses the wheel hub and bearing that hold to the wheel, and connects to the upper and lower control arms by way of the ball joints. The steering knuckle is also connected to the steering system (thus its name) by way of the tie rods. These components allow the wheels to spin, turn, and move up and down over bumps.

How does the steering knuckle work?

The steering knuckle houses the wheel hub (the wheel is connected to the hub with the lug nuts or bolts) and wheel bearing. On some vehicles, the hub is bolted to the steering knuckle; on others, it is pressed into the knuckle. Attached at the top and bottom of the steering knuckle, by way of the ball joints, are the control arms that allow the suspension to travel up and down. The steering knuckle is turned by the steering system, and it connects through an arm called a tie rod.

What are the symptoms related to a bad steering knuckle?

The steering knuckle itself does not often fail. It is possible for the knuckle to become damaged if the vehicle is in a crash, or if it encounters a large pothole. It is more likely that the components in and around the steering knuckle - ball joints, bearings, control arm bushings, tie rod ends - are worn. If indeed the steering knuckle is damaged, symptoms might include tires that are excessively worn on the inside and outside edges or the vehicle pulls to one side when driving. A damaged steering knuckle might present during a suspension alignment. The threads with which the brake caliper is connected to the steering knuckle may become damaged at some point during brake system service. If the threads are damaged, the knuckle should be replaced.