To say that Ford’s Fox body Mustang is a true American icon would be an understatement of epic proportions. Many of us grew up wishing we had one and idolizing those who did. Despite two distinct generations of Mustangs before it, it was the Fox body that gave birth to an entire industry all its own of aftermarket components and created a cult following that is sure to live on for decades to come. Faster, more powerful cars such as the Coyote-powered 2011 Mustang GT have come along, but nearly nineteen years after the last Fox body rolled off the assembly line, a list of aftermarket manufacturers a mile long are still producing parts for one of automotive history’s classics, proving these cars are as popular as ever.
Maximum Motorsports has been involved in the Mustang performance aftermarket for two decades, and the Fox body cars are still smack dab on their radar. As one of the leader’s in performance suspension components for the Mustang, they carry all of the components one would need to take their grip, handling, and traction to the next level, and that’s what we’re going to do today with Maximum’s complete 1990-93 Mustang Grip Box kit, which we’ll be installing in our Fox body here in the Power Automedia garage. In addition to the suspension itself, we’ll be overhauling the entire rolling package with new Cobra replica wheels from American Muscle wrapped in Nitto rubber, exhaust from Flowmaster, and a five lug conversion kit, also from American Muscle.
Maximum’s Mustang Grip Box Kit
The suspension system that we’ll be fitting to our ’92 Mustang is the top-of-the-line offering for the cars that represent the final rendition of the venerable Fox, and is intended for a street-driven car but incorporates the tuning elements necessary to make it right at home on the track. According to Maximum Motorsports owner and founder Chuck Schwynoch, the suspension geometry has been changed both front and rear to improve grip, handling, and traction.
Up front, Maximum has designed their own K-member and control arms that improves grip on the nose, while in the back, the OE four-link is transformed into a torque arm system. As part of the kit, Bilstein has created custom Sports Series front struts and rear shocks to Maximum’s specifications and are designed for front and rear coilover springs. These shocks and struts are designed with an aggressive “street” rate out of the box, that Schywnoch explains is high enough to be suitable to open track racing, but still within the range of something that you’d drive every day. “It’s not super soft – it’s much more drag race oriented, but for street handling purposes with the ability to go open tracking. It’s set up with a 375 pound front spring rate, and we limit ourselves to 400 pounds in the front for street-driven cars.”
In the front suspension, half of the effort is optimizing the roll center height – especially on a car that’s been lowered, which so many enthusiasts tend to do. Thus, Maximum Motorsports has raised the lower control arm pickup points up in the K-member to compensate for this, and to help restore the geometry to a more respectable height.
The torque arm system does a much better job of locating the rear axle, keeping it located side to side, and improving traction without hurting the overall handling ability.
The second goal is to create more positive caster to help improve the front grip. To do this – and we opted to forgo this on our project – Maximum moves the front wheels forward about 3/4-inch. You can also utilize their caster/camber plates that pulls the top of the struts back toward the firewall to add caster, as we will do, to keep from having to perform body work to match the new ball joint position.
In the rear, Maximum Motorsports has completely done away with the factory Mustang four-link suspension that was originally designed for a Ford Fairmont. These cars were intended for little more than driving to the grocery store, and doesn’t do the job of locating the chassis over the axle very well. Instead, the torque arm system keeps everything much more in line, according to Schwynoch.
“From drag racers, they hear of a torque arm and when they ask about it, they always assume its for road racing only. And if you talk to someone that’s a road racer and hasn’t heard much about torque arms, they assume it’s for drag racing. But it actually increases rear grip for both situations,” says Schwynoch. “The torque arm system does a much better job of locating the rear axle, keeping it located side to side, and improving traction without hurting the overall handling ability. This is one of the keys to the system, because you gain rear grip both in a straight line and going around a corner. It really shines when accelerating out of a corner.”
The rear lower control arms in this kit are much stiffer and sport precise bearings that inhibit fore and aft deflexion, keeping everything located. In turn, you don’t have deflection of the control arms or the stock rubber bushings. This serves to benefit straight line traction, because when you’re on the throttle, the tires move the axle forward, the axle pushes on the lower control arms, and that’s what moves the chassis down the road. Any kind of fore and aft deflection, according to Schwynoch, reduces how quickly the car reacts to the throttle and contributes to axle windup – also known as “wheel hop.”
This torque arm system from Maximum Motorsports utilizes a panhard bar to locate the axle side to side and keep it centered, which Schwynoch sees being much more precise as compared to the OE four link system. “When you allow the axle to move sideways, that’s a steering input at the back of the car. You can imagine being in the drivers seat and suddenly the back bumper moves sideways – the car is steering without you actually doing any of the steering. The car can feel quite unstable, and its something you get used to and don’t realize until you get in a car with a panhard bar.”
Continued Schwynoch, “You want your chassis movement controlled by your springs and sway bars and not by the suspension binding up or odd geometries in the suspension.”
As part of the kit, Bilstein has created custom Sports Series front struts and rear shocks to Maximum’s specifications and are designed for front and rear coilover springs. These shocks and struts are designed with an aggressive “street” rate out of the box, that Schywnoch explains is high enough to be suitable to open track racing, but still within the range of something that you’d drive every day.
The Maximum Motorsports Grip Box kit (Part # GB-2)
Because we’re rearranging the rear end of our Fox, from the 4-link style OEM suspension to a torque arm, we also have to modify the layout of our exhaust setup. In doing so, we’ve chosen Flowmaster’s iconic American Thunder Series cat-back exhaust system, featuring their Super 44 Series mufflers with an aggressive tone known only to Flowmaster.
• MM K-member (with 2-point brace)
• MM Front Control Arms
• MM Torque-arm
• MM Panhard Bar
• MM XL Series Full-length Subframe Connectors
• MM Coil-over Conversion Kit
• MM Caster/Camber Plates
• MM Aluminum Rear Lower Control Arms
• Bilstein HD series struts
• Bilstein HD series shocks
• MM Adjustable Rear Swaybar
• MM Aluminum Steering rack Bushings
• MM Solid Steering Shaft
• MM Bumpsteer Kit
• MM Strut Tower Brace
• MM Front Swaybar Relocation Kit
• Front Swaybar Bushings
• Front Swaybar End Links
Nitto’s NT05 Performance Radials
We’re leaving virtually no stone unturned in our effort to take the overall performance of our Fox body to the next level, and we certainly don’t want to cheat ourselves by running on a sub-par set of shoes. Thanks to the folks at Nitto Tires, however, that won’t be a concern as we mount up up a set of their NT05 max performance Radials. These tires are designed for the street and deliver precise and response handling and performance that’s sure to compliment our new Maximum Motorsports suspension system.
Additionally, the NT05 was developed through extensive computer simulation modeling and on-track testing. These rigorous development procedures helped produce a street tire that provides precise and responsive handling and performance. Knowing the tire is responding to your inputs will inspire our confidence.
If we’re going to take this project out and beat on when we’re finished – and no doubt we will – every part of the rolling setup needs to be up to the task. From the factory, the Fox body cars came equipped with four-bolt hubs but in order to increase the durability of this ride, we’re going to switch to a five-lug kit from American Muscle. This kit fits 1987 to 1993 Mustangs and reuses the stock brake components. As a complete conversion kit utilizing brand new parts, it features 28 spline five-lug axles from Superior Axle & Gears and includes the five-lug front rotors and rear drums, axles, wheel studs, axle bearings and seals, and two bottles of Royal Purple 75W90 gear oil.
Along with added strength, the five-lug setup provides us with many more wheel options on the market, and we’re taking that opportunity as our cue to bolt up a new set of wheels.
We’ve all seen the wheels that came standard on the 2003-04 “Terminator” Cobra’s on Fox bodies, and no doubt they go together exceptionally well, so to give our Fox a little makeover, we’ve selected American Muscle’s blacked-out Cobra replica wheels. These wheels are offered in 17×9 and 17×10.5 sizes in the American Muscle catalog.
Turning The Fox Into A Smooth Criminal
Maximum Motorsports does an exceptional job of providing detailed installation instructions with each component that comprises this kit, making it a relatively simple process that a novice technician should be able to complete in 2-4 days. All of the tool requirements are outline with each component so you’re not left searching for the right part tool for the job. While there’s far too much information to go through in detail, we’ll briefly walk you through this process.
We’ve chosen to start in the front of the car with our installation, and naturally, that begins with the heart of it all: the K-member. Before we can install the new K-member, we have to remove the factory one, and that means supporting the weight of the engine while we make the swap. With the K-member out, this is the time to to install our caster/camber plates and front struts and shocks from Bilstein.
The caster/camber plate package includes bottom plates, bearing plates, main plates, and spacers, along with a bump stop that we’ll forgo since we’re using the Bilstein shocks. Using the large center slot as a basis, we identify and passenger side main plates and begin our install. The bearing is installed onto the main plate, with a washer over each stud. The bottom plate then attach under the strut towers with 1/2-inch studs. Our Bilstein shock and strut assembly then secures to the caster/camber plates using the strut top retaining nut. One spacer bushing is required on top of the spherical bearing, under the strut top retaining nut, which is tightened once the car is on the ground.
With the engine still supported in the car and our new struts installed, we can now turn out attention back to the K-member. First, we attach the K-member brace, then raise the K-member into place, checking for the pinching of any components as its raised. Eight bolts are used to attach the K-member to the frame. Once tight, we need to square the K-member, which is accomplished using a plumb bob in a process that’s fully explained in the directions. Once we’re square and all of our K-member bolts are torqued, the brace can be removed and the engine can be gently lowered back down onto the K-member. We remove the engine hoist and reinstall the brace.
At this point we can also install our new steering rack. We raise the rack up into place, engaging it into the steering shaft itself as we go. We inserted the steering rack bolts through the rack bushings from the front of the rack, and then slide each bolt through the rack mounting sleeve in the K-member. We can also mount our new tie rod ends, utilizing the OE spindles. Of note, the factory spindles require minor modification to enlarge the tapered hole for the steering arm to 5/8-inch.
The MM K-member has two sets of mounting holes for our front control arms. The lower set is raised one inch from the stock location and should be used if the car is lowered, as ours is. To install the control arm, we first grease the exposed faces using supplied grease and slide the control arms into place on the K-member with the way bar mount facing forward.
Rear End Install
Transitioning from the factory 4-link style rear suspension to the new torque arm system requires a good bit of welding and other modifications to complete. Obviously we’ll have to drop the entire rear end housing assembly and measure and create the mounting points for our forward and upper torque boxes. Some welding is necessary to fabricate the mounting tabs on the subframe connectors for the lower control arms and the center pivot, along with the sway bar mount. Once we button up the rear sway bar, mount the rear coilovers, and the panhard bar, the axles are positioned back into the rear end housing and the rest of our axle and brake system pieced back together.
In our particular case, the Cobra-style wheels that we chose didn’t clear the brake rotors, requiring some minor clearance work on the rotors to create a proper fit. Also, we’ve done and is always recommended with any suspension overhaul such as this, after performing your own measurements and checks for alignment, be sure to take the car to an alignment shop to get everything as perfectly square as possible to insure the greatest performance.
Track Testing Coming…
Once a dragstrip engineered Mustang, our Fox body has everything it needs to handle the twisties with confidence. Maximum Motorsports utilized over 20 years of road racing experience when it came to designing their top-notch suspension kits. The craftsmanship speaks for itself as all the components fit like you would expect from American made go-fast pieces. Furthermore, our American Muscle wheels wrapped in Nitto’s ultra sticky NT05 tires are going to be fun to play with on both the road course and So Cal canyon roads. Stay tuned for our track testing article!