Whether you’re preparing your car for an event like an autocross or a track day, or you’re looking to be able to carve up the backroads and canyons even faster than before, it’s undeniable that using the right parts in your suspension setup is key.

The right suspension upgrades and setup will shed tenths off every corner on the track or at the autocross course. While there’s a lot of talk out there about springs, shocks, and coilovers, the sway bar tends to be one of the last suspension components people address. Let’s have a look at what sway bars are, how they impact a car’s handling characteristics, and how to decide which one is right for you.

What are Sway Bars?

As the name explains unambiguously, a sway bar, also known as an anti-roll bar, works together with the suspension to keep the car geometry as close to the optimum parameters as possible. The sway bar connects the otherwise independent suspension linkages of the left and right wheel of the same axle.

During cornering, the inside wheel behaves differently from the outer wheel. The outer suspension compresses while the inner suspension expands. The sway bar connects the two wheels and causes them to stray less from their neutral position and rather follow each other’s behavior more closely.

In other words, the sway bar acts like a torsion spring, withholding some of the cornering energy and thus maintaining a high degree of stability while allowing for some independent motion of the suspension.

What to Expect From Upgraded Sway Bars?

The most noticeable difference that you would feel from installing thicker sway bars would be an overall feeling of tightness, in the sense of less body roll, regardless if mounted on the front axle, rear axle, or both. Mostly, the sway bar will keep camber angles true to their original settings as much as possible. As a result, you will notice that tires warm up faster, steering feels more precise, and that it is also easier to recover when losing grip.

On the other hand, stiff sway bars will also get the tires running at higher temperatures and thus increasing degradation and blistering. While your car will be more precise, it will also react harsher to any steering inputs and cornering. Finally, stiff sway bars and bumpy tracks do not tend to go well together. Neither do stiff sway bars and wet tracks.

So, what is there to be done? Skip the anti-roll bars altogether? Definitely not. The sway bar plays an important role in your car’s suspension setup and does wonders for shaving tenths off of your lap time.

One thing that is important to note is that you shouldn’t just max out the stiffness of your sway bars, and you shouldn’t run without them. In order to make sure that your setup is dialed in properly, it’s important to do some research to figure out what sort of balance of sway bar thicknesses would be best to run both in the front and in the rear. Odds are that somebody has installed and documented some sort of results or general experience running whatever sway bars you may be considering for your car. Usually, the quickest way to find this information is on forums dedicated to discussions around ownership, maintenance, and modification of your make and model.

Sway Bars on FWD, RWD, and AWD Cars

Crucially, one thing to note is that not all sway bars are the same. In fact, your car’s sway bar will have a different effect on the behavior of the vehicle depending on the powertrain layout. Let’s have a brief look at how that works.

Front wheel drive (FWD) cars tend to understeer, because they use the front tires both for turning and putting power down to the ground. A stiffer sway bar on the rear axle will reduce this effect and improve handling over a stock sway bar. Go too stiff in the rear, and you might find yourself encountering lift-off oversteer. This is when the weight transfer from the rear to the front of the car when you lift off the throttle induces oversteer.

Rear wheel drive (RWD) cars on the other hand, tend to oversteer as the rear wheels are powered and will attempt to throw the rear end out into the corner sooner than the front wheels can turn. Installing a stiffer sway bar on the front axle will reduce oversteer by tightening up the front suspension.

You might have heard the myth saying RWD cars don’t understeer. Any car can understeer, although RWD drivetrains are generally less likely to. Regardless, you can counteract understeer in FWD and RWD cars the same way: running a stiffer rear sway bar.

All wheel drive (AWD) cars will either understeer or oversteer, depending on the OEM setup. Knowing how to treat the behavior on FWD and RWD vehicles, you only need to extend the same theories to an AWD drivetrain. In other words: understeering AWD – stiffer rear sway bar, oversteering AWD – stiffer front sway bar.

A Sway Bar for Each Discipline

No matter how it may seem at times, there is no magical one-size-fits-all sway bar. As mentioned earlier, the craftsmanship of suspension tuning comes from balancing components. Small setting tweaking will earn more performance points than jumping to the extreme.

Depending on your racing discipline, a different setup will be required for the suspension and implicitly for your front and/or rear sway bar. Let’s have a look at the main choices for common racing disciplines.


Two highly modified BMWs, an E92 and E30, drifting on track.

Drifting is all about throwing out that rear end and sliding around the corner, then preparing to switch it up for the upcoming turn. In the case of drifting, the name of the game is oversteer. Since the majority of drift cars are rear wheel drive, you generally go for a rear sway bar intended to help set the initial amount of oversteer. As for the front sway bar, drift cars tend to actually run a slightly stiffer front than rear. Or, in cases where the sway bar interrupts the steering angle, some drifters opt for removing the sway bar altogether.

Note: if once installed, the sway bar doesn’t react as you may expect, there’s a good chance that your overall suspension setup (springs and/or shocks) is already too stiff and the rear sway bar isn’t making as significant of an impact..

Time Attack

Time attack events are all about mastering racing lines and carrying the most amount of speed into and out of each corner. As such, you don’t want your car to either understeer or oversteer but generate the most amount of grip possible. In this case, depending on your drivetrain layout, you will have to tune your front and rear sway bars to work together, keeping the car as stable at the limits as possible on the asphalt.

Generally, time attack events will see cars running a stiffer suspension. The trick is to avoid stiffening up your sway bars to the point where you’re losing grip going into every corner. The only real way to find your car’s suspension (and grip) limit is by slightly adjusting them then testing on the track. The process may be slow and painful but tends to yield the best results.

Endurance Racing

Endurance racing is a class of its own when it comes to component reliability and function. Endurance means a lot of laps; it means worn tires and it means making mistakes due to fatigue. As such, a more forgiving suspension setup is advisable since tires will also behave differently as they wear. Setting up the sway bars with fresh tires may lead to unexpected behavior as the laps add up.

Some Final Notes

There is so much information on suspension tuning that it would require two lifetimes to cover and test out everything. Thankfully, once you’ve gotten to understand the basics, you can experiment on your own and see what works for your car.

There are, however, a few things to consider when upgrading or setting up your car’s sway bars, on top of everything we discussed so far.

  1. Don’t fully trust the numbers. Sway bars rarely have the exact stiffness mentioned on the sticker. Unless you’re racing at a professional level or you have plenty of time on your hands, going and calculating the real stiffness via the torsional modulus of rigidity, inner and outer diameter of the tube, the length of the torsion bar and length of the cantilevers – not really worth it. Instead, if you keep adjusting your suspension and the behavior doesn’t add up, consider trying a different sway bar.

  2. A bigger bar isn’t necessarily a stiffer one. Take into account the fact that the stiffness or sway bars comes from the cross-section of the tube. As such, you may get hollow sway bars with a larger outer diameter, or solid sway bars with a smaller outer diameter, behaving the same.

  3. Once again, remember how everything is about balancing the elements. A stiffer sway bar is not always better. You may want to stiffen up your suspension on dry, grippy track but you will want to allow for some wiggle room on questionable grip surfaces or damp track.

Go Out There and Test It Out

Now that you understand the fundamentals of a good sway bar setup, it’s time to put your knowledge to the test. The only way to find the perfect setup for your car is to put some time in. Remember, incremental improvements are the key to success here.