Sway Bar & Sway Bar Kits for 2021 Subaru WRX STI Base

A sway bar is a length of spring steel running across your Subaru WRX STI, mounted to the chassis in the middle and connected to the suspension at each end. Twisting is how it does its job, and it only twists when one wheel moves relative to the other.

If you are wondering what is a sway bar on a car in practical terms, that twisting is the whole of it. Catalogs list the same part as a stabilizer bar, an anti sway bar or an anti roll bar depending on the manufacturer.

What Does a Sway Bar Do on Your Subaru WRX STI

Take a corner and weight transfers to the outside wheels. The outside suspension compresses, the inside extends, and the body leans over.

That lean costs you more than ride comfort. As the vehicle sways over, the outside tires are pushed onto their outer shoulders and the inside tires unload, so the tire doing the most work is running at the worst angle it will see all corner while the one that could be helping is barely loaded.

A car sway bar limits how far that goes. Because both ends connect to opposite sides of the suspension, one wheel compressing forces the bar to twist along its length, and the bar resists. Load gets transferred back across to the lightly loaded side, the body stays flatter, and the tires stay closer to the angle they were designed to work at.

The reason it does this without ruining the ride is that it only reacts to one wheel moving relative to the other. Drive over a speed bump squarely and both ends move together, nothing twists, and the bar contributes nothing at all.

Sway Bar or Trailer Sway Control

Two different products share the name and they have nothing to do with each other.

A trailer sway bar or sway bar hitch is towing equipment. It attaches between the tow vehicle and the trailer and resists the trailer moving side to side behind you. A sway bar for a camper is the same idea.

What is covered here is suspension sway bars, which bolt to the vehicle and control how much the body leans in a corner. They do help a tow vehicle feel more settled, particularly a rear bar on a truck carrying weight, though they are not a substitute for proper weight distribution and dedicated trailer sway control.

Bad Subaru WRX STI Sway Bar Symptoms and What They Actually Point To

Almost every complaint attributed to a sway bar turns out to be the parts holding it rather than the bar itself.

Squeaking or creaking over speed bumps and driveways that changes with the weather is the mount bushings drying out and hardening. A light rattle over sharp edges at low speed is the end links. More lean through corners with the vehicle feeling looser than it used to is usually both, gradually, over several years.

That is worth knowing before ordering, because the diagnosis changes the part. The bar is shaped spring steel that twists and returns, and nothing about that process wears it out. A twenty year old bar is almost always still the correct rate for the vehicle.

Bad sway bar symptoms in the sense of the bar itself having failed are rare, and when they do occur the cause is usually corrosion or impact rather than use.

How Long Your Subaru WRX STI Sway Bar and Its Parts Last

There is no service interval for any of it, because the answer depends on climate and road surface more than mileage.

Factory rubber mount bushings commonly start making noise somewhere between 50,000 and 100,000 miles, and vehicles in salt states, hot climates or on rough surfaces reach that considerably sooner. Links wear on a similar schedule, though a ball jointed link fails once its boot splits rather than gradually, which is why one side often goes well before the other.

The bar itself outlasts all of it on any vehicle that has not been damaged or badly corroded.

What makes this awkward to notice is that none of it fails suddenly. The performance fades over several years while the driver adapts, and the noise arrives last rather than first. A vehicle that felt planted when you bought it and feels vague now has not developed a soft bar, it has worn out everything holding the bar in place.

If your Subaru WRX STI has covered serious distance on original rubber, the parts are due whether or not anything is making noise yet.

When Does Your Subaru WRX STI Sway Bar Itself Need Replacing

There are three situations where the bar rather than its hardware is the problem.

Corrosion is the most common of the three. A bar that has spent fifteen winters in a salt state can lose enough section at the mounting points or the bends to be genuinely weakened, and heavy scale rather than surface rust is the sign.

Impact damage is the second, because an off road hit or a hard strike underneath can bend a bar, and a bent bar will not sit square in its mounts, which means it preloads itself and works unevenly from side to side.

The third is a deliberate upgrade rather than a repair, where a heavier bar is fitted to change the vehicle's balance.

Outside those three, sway bar replacement usually means replacing the bushings, the links or the brackets while keeping the original bar. That is also the cheaper repair by a wide margin.

Subaru WRX STI Front Sway Bar and Rear Sway Bar

Both resist lean and they pull the vehicle's balance in opposite directions.

A stiffer front sway bar resists front lean harder, which loads the outside front tire more and pushes the vehicle toward understeer, where the nose runs wide.

A stiffer rear sway bar does the same at the back, which frees the front up and allows the vehicle to turn in more readily.

Most vehicles leave the factory tuned toward understeer because it is safer and more predictable, which is why adding or upgrading a rear sway bar is the most common change people make. Trucks and SUVs respond particularly well, since they often have very little resistance to rear vehicle sway from the factory and gain noticeable stability under load.

Subaru WRX STI Sway Bar Replacement Cost

Sway bar replacement cost depends almost entirely on which part of the assembly is actually being replaced.

Bushings and links are inexpensive, the labor is short because nothing needs pressing, and no alignment is required afterward. That combination makes it one of the cheaper repairs available on any vehicle.

Replacing the bar itself costs more as a part and about the same in labor, since the bar unbolts at four points regardless of whether it is going back on or being swapped.

What inflates quotes in either case is corrosion, because the bracket bolts and link nuts sit in poor positions and seize regularly. A shop that has priced in cutting fasteners off will quote higher than one that has assumed everything comes apart cleanly.

Subaru WRX STI Sway Bar Kits and What They Contain

Kits group the parts that work together, which matters because the bar depends on all of them.

A sway bar kit built around an upgraded bar typically includes the bar, mount bushings and brackets, and sometimes the links, since a heavier bar loads the links and mounting points harder than the original did.

Service and hardware kits cover the wear parts for a bar already on the vehicle, which is the more common purchase by some distance.

If you are fitting a heavier bar, look at the links and the mounting points at the same time. A new bar working through tired bushings and worn links will not deliver what it is capable of, and the mounts take more load than they were originally specified for.

Removing and Refitting Your Subaru WRX STI Sway Bar

The bar unbolts at four points and nothing needs pressing, so this is among the more approachable suspension jobs.

Expect resistance at the bracket bolts and the link nuts, and allow time for them rather than being caught out. Penetrating fluid applied the night before is worth more than force on the day.

Clamp the mount brackets down to their full torque figure, because the bar has to rotate inside the bushing rather than the bushing turning inside the bracket, and stopping short for fear of crushing polyurethane is what causes a bushing to spin and wear out early.

Set link length with the vehicle on all four wheels rather than hanging, and never force a link to reach, since a preloaded bar is part way through its travel before the vehicle has moved.

Fit both sides before final tightening so the bar sits square, and check clearance through the full range of suspension travel. No wheel alignment is needed after any of this work.

Find Sway Bars and Sway Bar Parts for Your Subaru WRX STI

Worn mounts are fixed with sway bar bushings, and a cracked or rusted mount can be replaced with a new sway bar bracket.

Select your Subaru WRX STI to see the front sway bar and rear sway bar components listed for it, including bushings, links, brackets and complete kits. Every Nolathane component is backed by our warranty, a fitment guarantee and 60 day returns.