Wes Duenkel
June 19, 2019
Contributers: Wes Duenkel

Performance has generally increased with each successive Mustang generation that rolls off the assembly line. Sure, the new cars are faster, but when it comes to the giggles-per-gallon quotient, it's still hard to beat a Fox-body Mustang. Low weight and tidy proportions make the 1979-1993 Mustang a hoot to drive, and their simplicity makes improvements straightforward and relatively inexpensive. On the Fox-body suspension tree, there's a lot of low-hanging fruit.

The Mustang specialists at Steeda Autosports have been making Fox-bodies faster since they were new. That's not to say Steeda rests on their laurels. The evolution of Steeda's products reflects the experience they've gained in their 30 years of business.

Using a Mustang already equipped with Steeda's G/Trac Stage 1 Suspension Kit, we wanted to take the Mustang one step further by installing Steeda's sway bars paired with tried-and-true Koni Sport adjustable struts and shocks.

Steeda's front sway bar is 1-3/8-inch diameter and features billet and welded sway bar ends, polyurethane pivot bushings, and new sway bar end link bushings. The Steeda front sway bar is 1/16-inch larger in diameter and 15% stiffer than the factory-installed bar on the 1985-1993 Mustang, yet the tubular design saves four pounds. The factory front sway bar end links on this Mustang were bent, we opted for a new set of new polyurethane sway bar end links. Furthermore, Steeda's lightweight front sway bar mounts replaced the flimsy stock pieces.

In theory, increasing the front sway bar rate increases understeer, which the Fox Mustang already has in spades. So, we chose Steeda's rear sway bar to balance the handling of this Mustang. Compared to the stock 13/16-inch rear bar, the Steeda rear sway bar measures 1-inch, making it significantly stiffer than the factory piece on this 1991 GT. This will help further reduce front-end plow from our Mustang. The Steeda Rear Sway Bar features thick billet steel ends that are welded to the bar. It's beefy. So beefy, in fact, that Steeda guarantees the bar from breakage for life.

To complement the newfound spring it this Mustang's step, we chose a set of Koni Sport adjustable struts and shocks. The Koni Sports are a proven upgrade to match higher spring and sway bar rates to make a Mustang corner flatter and faster. The Koni Sports are direct replacements for the factory struts and shocks on 1987-1993 Mustangs and feature a rebound damping adjustment.

Adjusting the rebound (extension) of the damper changes the rate of weight transfer around the chassis. Looser (less) rebound transfers weight faster, while tighter (more) rebound transfers weight more slowly. Generally speaking, rebound changes the balance of the chassis during transitions, while sway bars change the balance of the chassis in the middle of a corner. More rebound damping makes the car feel more "tied down," but too much will actually reduce cornering grip.

Installing the sway bars, struts, and shocks was pretty simple. With the new suspension bits, this 1991 Mustang GT was markedly more agile. After cranking the steering wheel, the chassis rolls less and feels more settled—especially with some rebound damping cranked into the Koni's. Even though the Mustang feels livelier, there wasn't any increase in ride harshness. In fact, wheel impacts (like potholes) were soaked up dramatically better than before, which we credit the Koni's refined high-speed compression damping as well as the new sway bar bushings and end links.

All in all, we were greatly impressed. Check out the following photos and captions for the details.

To make this 1991 Mustang GT more nimble, Steeda sent their front and rear sway bars, Koni Sport shocks and struts, and Steeda lightweight front sway bar brackets.
With the front control arm supported with a floor jack, we began by removing the factory spindle-to-strut bolts.
Then, we removed the strut rod nut.
While the jack supported the lower control arm, we removed the struts.
The Koni Sport strut (bottom) is a direct replacement for the factory strut (top).
Before installing the Koni Sport strut, we transferred the bump stop and dust cover from the old struts to the Koni strut.
Then, we installed the Koni Sport strut by first feeding the strut rod through the caster/camber plate's bearing.
We used the supplied hardware from Koni to tighten the strut rod in the caster/camber plate bearing.
Then, we installed the strut-to-spindle bolts and torqued them to 150 ft-lb.
With the Koni front strut installation complete, we removed the sway bar end links.
While Steeda includes new end link bushings with their front sway bar, we found our factory sway bar end links (top) were bent on both sides of the car. Rather than upgrade the bent end links with the supplied bushings, we replaced the links entirely with heavier-duty end links from Steeda (bottom).
Next, we removed the front sway bar brackets from the fame rail and dropped the factory front sway bar.
Compared to the flimsy and deformed stockers (left), the Steeda billet aluminum brackets (right) are much sturdier.
We also compared the factory sway bar (top) with the Steeda front sway bar (bottom). The Steeda front sway bar is 1/16-inch larger in diameter and 15% stiffer than the factory-installed bar on this 1991 Mustang GT, yet the tubular design saves four pounds.
We used the included waterproof grease to lubricate the supplied sway bar bushings.
After inserting the sway bar bushings into the Steeda lightweight front sway bar brackets, we fastened them to the frame rail with the supplied hardware.
Then, we installed the new sway bar end links.
Steeda also includes four steering rack limiters in case the larger sway bar interferes with the wheels when the steering is at full lock. We pulled back the steering rack boots and installed a limiter on each side. Those with larger wheel and tire combinations might need to install all four limiters.
With the front finished, we moved our attention to the rear. First, we removed the existing upper shock mounts and rear shocks.
As with the front struts, the Koni Sport rear shocks are direct replacements for the factory pieces.
With half of the top shock bushing slipped over the shock shaft, we installed the Koni Sport rear shocks.
Koni uses two nuts to lock the upper shock mount into place. We used a crow's foot and a socket to lock them together. (Note the Koni Sport's rebound adjustment at the top of the shaft.)
With the Koni Sport shocks installed, we removed the factory rear sway bar.
The factory rear sway bar (top) measured 13/16-inch, while the Steeda rear sway bar is 1-inch. Note beefiness of the Steeda rear sway bar mounts!
We used the supplied hardware to install the Steeda rear sway bar.
Koni includes these handy adjustment knobs to set the rebound damping of the Koni Sport dampers.
This chart shows the adjustment range of the Koni Sport's rebound damping when compared to a typical original equipment (OE) shock or strut. Two things to note: 1) While the rebound damping range is quite a bit more than the O.E. part, but the compression (bottom) is similar. This means the Koni Sports remain comfortable over bumps, but control chassis movement more effectively than the O.E. part, 2) The Koni Sport has less damping at the higher velocity range on compression than the O.E. curve. This may explain why the Koni Sport helps the suspension "soak up" potholes and other hard impacts better than the O.E. dampers.

 

 

Sources:

Steeda
800-950-0774
steeda.com

KONI North America
859-586-4100
Koni-na.com