Sway Bars Explained: What Do They Do & How Do They Work?

Tons of components affect the way your vehicle handles as you drive down the road. One of the most effective car components that stabilize your vehicle is the sway bar.

But what exactly are sway bars, and how do they work?

In this guide, we’ll explain everything you need to know about sway bars, whether you’re replacing your sway bar or just trying to figure out how they work.

What Is a Sway Bar?

A sway bar, also known as an anti-sway bar, anti-roll bar, or a stabilizer bar, is typically a u-shaped metal bar connected to the strut or control arm, located by each of the vehicle’s wheels. Not every vehicle has a sway bar, and there are multiple types.

Anti-roll or "sway bar"

Sometimes sway bars don’t come in their typical “u shape” and some sway bars are solid while others are hollow. While a sway bar’s exact physical appearance can vary, sway bars all serve the same purpose.

What Does It Do?

So what do sway bars or anti-roll bars do?

The name “sway bar” is a bit of a misnomer, and it’s why many people refer to them as anti-sway bars or anti-roll bars. That’s because they limit how much your vehicle sways when rounding corners or while turning.

Mazda Miata body rolling
The sway bars in this Miata are working exceptionally hard.

The simplest explanation for a sway bar’s purpose is to keep all four of your wheels on the ground to prevent you from accidentally flipping your vehicle.

How Do Sway Bars Work?

Knowing what a stabilizer bar does is one thing — but knowing how they do it is another topic altogether. So how does a sway bar work? We’re glad you asked.

As your car turns, it puts a lot of pressure on your car’s suspension and steering system. Without anywhere to put that tension, your vehicle can end up “swaying” and if the problem is severe enough, your car can end up flipping.

Your vehicle’s sway bars work by providing an outlet for all that force; by controlling where it goes, your vehicle can stay stable and handle those sharp turns a little better. Sway bars do this by twisting as your vehicle turns.

As soon as your vehicle is done turning, the sway bars straighten back out. You might think that all this twisting and turning would wear out your sway bar, but it’s built to handle this motion, and they typically last your vehicle’s lifetime.

However, the mounting bushings can wear out, and you might need to replace them to eliminate any excess play in your sway bar.

Diagram of how an anti-sway bar works
How a stay bar works when making a right turn.

Different Kinds of Sway Bars

While most sway bars are a u-shaped bar that twists to help keep your vehicle from flipping, there are several different kinds of sway bars used today.

The four most common sway bars are:

  • solid sway bars
  • hollow (tubular) sway bars
  • splined sway bars
  • active anti-roll bar system

They all perform the same function, but how they do it, varies slightly.

Solid Sway Bars

Solid sway bars are the most common type of sway bars found in modern vehicles. They are a solid u-shaped metal bar that connects one wheel assembly to the other on the same axle.

They work by twisting as you round corners to displace the extra tension. Solid sway bars are long-lasting and durable, but they are a bit heavy.

Hollow vs Solid Sway Bars

Hollow Sway Bars

Hollow or tubular sway bars are identical to solid sway bars in every way but one. Instead of a solid metal bar, the sway bar is hollow on the inside. This has several performance benefits, and they are typically long-lasting as well.

Hollow sway bars are a little more expensive than solid sway bars, but their reduced weight makes them more popular among performance vehicles.

Splined Sway Bars

While most sway bars are u-shaped, there are a few that are completely straight. These are known as splined sway bars and can be both hollow or solid. They work in the same way as a traditional sway bar, but they spin directly into the connecting arms.

Splined sway bars are common in racing and performance vehicles. You can easily adjust them, allowing you to adjust your track car for the course you’re racing that day.

Hollow splined sway bars for race use

Active Anti-Roll Bar System

While hollow sway bars and splined sway bars are common among performance vehicles and race cars, another system puts both those to shame. It’s the active anti-roll bar system.

This is an electronic system controlled by your vehicle’s ECU. The computer works with sensors and actuators to change your vehicle’s suspension as you round corners.

By lowering one side of your vehicle to adjust for the shifting momentum, your car eliminates the need for a traditional sway bar.

For you, it means less weight, which is a considerable performance boost. However, you’ll only see these systems on extremely high-end vehicles.

Other brands use sway bars but have a method of adjusting their stiffness in real time. Development in this space is changing fast, so there will surely be more variations in future as well.

Porsche's active anti-roll bar system
Porsche’s active anti-roll system.

How to Replace and Adjust Your Sway Bar

While it’s uncommon for a sway bar to fail, the bushings often wear out. Even if you’re just replacing the bushings, you’ll need to remove the entire sway bar.

The exact steps vary by vehicle, but it’s not as hard as you might think as long as you have a quality mechanic’s tool set and some other equipment. To make the job easy you’ll want to have:

  • a vehicle jack
  • jack stands
  • a ½ drive ratchet set, and
  • a ⅜ drive ratchet set

Start by jacking up the front or rear of the vehicle — if your sway bar is in the rear of your vehicle, jack up the rear. If it’s in the front, jack up the front. While it’s not always necessary to remove the tires, it’ll make the job far easier if you do.

From there, remove the bolts connecting the sway bar to the sway bar links. After this, you can move to the bolts holding the sway bar bushings to your vehicle’s frame.

Once you have removed both sets of bolts, try to pry the sway bar from the housing gently. Often the sway bar will hit various components before you can thoroughly remove it.

Remove one side at a time and pull the sway bar out of the wheel well. Since the sway bar is typically u-shaped, you won’t be able to pull it straight out.

After successfully removing the sway bar, you can replace the bushings or simply replace the entire sway bar.

From there, reinstall the sway bar following the same steps. It might take some work to get the sway bar back into place, but if you got the old sway bar out that way, the new one will fit right in.

Adjusting a Splined Sway Bar

While most sway bars aren’t easy to adjust, splined sway bars are quite the opposite. All you need to do is spin the sway bar one way or the other to shift it over. The farther you shift the sway bar, the more it’ll affect how your vehicle can handle turning in that direction.

However, the tradeoff is that it won’t prevent rolling in the other direction as effectively. It’s perfect for vehicles that are constantly turning in the same direction on the track.

A sway bar that is perfectly centered will prevent rolling equally no matter which direction you’re turning — which is precisely what most daily drivers want.

Difference Between a Sway Bar and Shock Absorbers/Struts

While both sway bars and shock absorbers affect your vehicle’s suspension, they are entirely different components that work in entirely different ways.

Shock absorbers perform a ton of nifty features, but keeping your car from twisting and swaying isn’t one of them. Instead, shock absorbers keep your vehicle from bouncing excessively and give you a smooth and comfortable ride.

Moreover, sway bars are a single function component. They keep you steady and help you control your vehicle while you’re turning, but they don’t help level your vehicle or perform any other suspension like functions.

Difference Between a Torsion Bar and a Sway Bar

Sway bars and torsion bars are two of the most commonly confused car components. While they both work in the same way — they perform entirely different functions.

Sway bars keep your vehicle from rolling, and torsion bars replace your vehicle’s leaf springs.

Simply put, torsion bars are a suspension leveling component, while sway bars are an anti-roll device.

Sway Bars: The Final Twist

Everything in your vehicle works in perfect symphony — and sway bars are no different. They connect to your vehicle’s struts or control arms, and as these components compress and shift, the sway bar twists.

If you’re still struggling to answer how do sway bars work — just know that they twist, and this keeps your vehicle from doing the same.

Older vehicles didn’t have sway bars, but as engineers mastered the physics behind vehicles, they found that these innovative devices improved performance and saved lives too.

So, next time you hit that corner a little too fast, thank that sway bar for keeping your wheels on the tarmac.

What’s your take on the different types of sway bars? Which one worked well for you? Tell us about your experience in the comments below!

1 comment

  1. On my 2006 Nissan 350z roadster I installed a skunk2 plenum with a spacing of 5/8″. Now the existing support bar does not fit and I need a different front strut bar. Do you know of an option that will not interfere with the hood, while also help to stiffen the right and left sides of the car?

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