What is a Steering Knuckle and Why is it Important?

The steering knuckle is chunky piece of steel with several protruding arms located right behind your front wheels. It connects the wheel hub (or spindle) to the suspension. The disc brake caliper mounts to the knuckle.

So what exactly is the steering knuckle and what does it do? Let's find out.

Knuckle drawing

Image Credit: Clear Mechanic

Also known as a wheel carrier or an upright, the steering knuckle is the last part in the steering system. There’s one steering knuckle attached to each front wheel, and its purpose is to turn your wheel when you steer.

How a Steering Knuckle Helps Your Vehicle Change Direction

The top and bottom arms of the steering knuckle attach to the suspension system via pivots called "ball joints". The ball joints let the knuckle pivot left or right. They also keep the knuckle in a vertical position. The steering knuckle also has a lateral arm that connects to a tie rod.

When you steer, the tie rod either pushes the lateral arm outward or pulls it inward, depending on the direction the steering wheel is turned. There are tie rods on both sides of a vehicle. When the lateral arm on one side is pushed outward, the other lateral arm is pulled inward at the same time. This turns the knuckles and front wheels in unison.

Why a Broken Steering Knuckle is a Big Deal

Broken knuckle

A steering knuckle is very sturdy. During normal use they usually last the life of the vehicle. However, if you have a minor collision, hit a really big pothole, or slide into a curb, you might damage the knuckle. If the knuckle breaks, your vehicle will be obviously disabled.

When you have a cracked or bent steering knuckle, your vehicle might seem like you could still drive it. But you really shouldn't. There are a few things could go wrong.

  • Your wheel alignment will be thrown out of whack. This leads to uneven tire wear and poor handling.
  • The damaged part can put additional stress on the ball joints. Ball joints can break suddenly.

If a ball joint breaks, it will suddenly become very difficult to steer, and you may loose control of the vehicle. This is obviously very dangerous. If you suspect that a steering knuckle is damaged, you should inspect it immediately.

How to Know if Your Steering Knuckle is Damaged

Removing the wheel and tire (or lifting the vehicle) to visually inspect your steering knuckle can be a cumbersome task. The good news is that there are symptoms to tell you when it’s time to take a look. The sooner you detect the following symptoms and catch the problem, the better.

  • One front wheel appears more tilted than the other.
  • Squealing noise when turning.
  • The vehicle pulls to the left or right.
  • Crooked steering wheel when driving straight.
  • The vehicle corners worse when steering in one direction than the other.

The best way to determine for sure if your steering knuckle is bent or cracked is to visually inspect it and/or to compare it to the other steering knuckle.

How to Deal With a Broken Steering Knuckle

A broken steering knuckle is unsafe to drive on at all. It needs immediate replacement. With the right tools and a comprehensive tutorial you should be able to replace it in a matter of two or three hours. You can buy an OEM steering knuckle online at a reasonable price.

Keep in mind that replacing a steering knuckle will likely affect your car’s alignment settings. We suggest taking your car in for an alignment after doing the job.