What Is A Ball Joint And Why Is It Important?

Ball joints may be small and simple parts. Yet, they’re a crucial part of your Subaru’s steering and suspension systems. In this guide, we'll talk about ball joints and why they're important.

What Is A Ball Joint?

If you look just behind the front wheels, you'll find a part that looks like this:

Subaru ball joint

Part #20206AJ000: Ball joint for select 1988-2020 Subaru models

That's one of the ball joints on your Subaru. Depending on your Subaru model, your car has either:

  • 2 lower ball joints
  • 4 ball joints (2 upper, 2 lower)

A ball joint is a spherical bearing that connects the control arms to the steering knuckles. You would find ball joints on pretty much every vehicle ever made. A ball joint works like a human hip joint because it has a similar ball-and-socket design.

The Components Of A Ball Joint

Ball joint components

A ball joint looks like a small and simple part. But it comes with many different components that work together. The main components include:

  • Ball stud
  • Dust cover
  • Ball seat
  • Urethane ring
  • Plug
  • Spring seat

Ball joints also come with supporting parts like studs (aka bolts). Ball joint bolts secure the ball joint to the control arms. Some ball joint bolts are fully integrated into the control arm, and some aren't.

Do you need to replace one of your ball joint bolts? Trying to find out your Subaru ball joint bolt size would be a waste of time. Instead, look up your Subaru model in our catalog of OEM ball joints and related components. You'll find the right ball joint bolt part number for your model in an instant. For example, this Subaru ball joint stud is made for a handful of 2010-2014 Subaru models.

Why Does Your Car Need Ball Joints?

Without ball joints, your wheels couldn't turn left or right, and the wheels couldn't move up or down. The ball-and-socket design of the ball joints make it possible for the ball joints to act as pivot points. In other words, they enable your wheels to move left and right and up or down without restriction. A ball joint connects to two parts:

  • The control arm
  • The wheel hub via a spindle

This setup enables the ball joint to keep the wheel in place and let it pivot left and right.

What Happens When Your Ball Joints Fail?

Ball joints usually last a long time. But they can fail. When that happens, you won't be able to drive your vehicle. That's why it's important to look out for signs of failing ball joints:

  • Clunking, squeaking, or creaking noise
  • Misalignment
  • The vehicle drifting left or right
  • Excessive tire wear

What happens when one of your ball joints completely fails? The wheel to which it's attached will likely splay out. It literally becomes detached from the suspension. When that happens, you can't drive your car until you fix the ball joint. It can be a catastrophic situation if the ball joint fails on the road.

If you suspect that you may have a failing ball joint, this diagnostic guide will help you confirm it.