The Detroit Speed Fox Short Long Arm Conversion System is optimized for factory 1987-1993 V8 Mustang K-members and aftermarket K-members, ensuring seamless integration into high-performance builds. Some fabrication is required, but the result is a modernized, precision-tuned suspension that outperforms factory limitations.

Fox-platform Fords are amazing creatures. Thanks to Detroit Speed’s new SLA conversion, they have the potential to be even more remarkable. The company’s new SLA conversion uses a fresh design and new hardware to transform front suspension function and allows for a wide range of adjustment for street and competition driving.

If there’s a shortcoming, it’s in the handling department. That’s because the MacPherson strut front end can be limiting in terms of adjustment when ultimate cornering grip is your bag. But fret not Mustang fans, there is a solution — Detroit Speed’s new SLA (Short-Long Arm) Conversion Systems. Detroit Speed and Engineering has released three packages that include double-adjustable, single-adjustable or non-adjustable shocks.

The team at Detroit Speed has completed extensive testing on a variety of Fox Mustangs, including this racy Coupe. Designed for serious performance applications, this system allows clearance for 275/35R18 tires on a 10-inch rim while maintaining full steering lock.

There’s no question that Fox Fords thrive in the street environment, on the drag strip, and can even be modified for handling in autocross, drifting, and road course situations. The lightweight, straightforward unibody construction offers a world of possibilities giving owners the chance to have fun no matter the occasion.

The Short-Long arm geometry allows for optimized camber gain and roll center height for better handling stability.

Before getting into the details, let’s look at the stock MacPherson suspension found on the Fox Mustangs (and Capris, Granadas, Lincoln Mark VIIs, etc.). This arrangement was popular in the late 1970s and 1980s on many vehicles. The system was affordable to manufacture and simple in design, which made it perfect for the range of Fox vehicles. It typically consists of an upper strut mount, MacPherson strut, coil spring, and a lower A-arm. The K-member serves at the engine cradle and locates the top of the coil springs. Combined with a rack-and-pinion steering setup, weight is kept to a minimum.

Robust tubular upper (shown) and lower control arms improve suspension geometry and reduce deflection.

With bolt-in modifications, they perform well on the drag strip, and even in handling situations. But it can quickly reach its limitations in the handling arena. This is mainly due to the relatively small window of suspension and/or alignment tuning.

The issues lie in the geometry, which changes as the suspension travels through its range of motion. This change results in unwanted camber gain. Camber gain is the change in a wheel’s camber angle (the angle at which the tire leans inward or outward) as the suspension compresses or when the vehicle leans in a corner. Controlling camber is important as it helps tire’s ability to remain compliant with the road or track surface during cornering and braking. Excessive change in camber during cornering or
braking prevents the tire from remaining flat on the surface and thus will reduce the contact patch. It can also lead to unpredictable handling characteristics.

The Detroit Speed’s Short-Long Arm (SLA) Suspension Conversion addresses these issues and offers a complete upgrade in one kit.

“Designed to work on 1979-1993 Mustangs (along with the 1979-’86 Mercury Capri), our suspension redefines Fox body
handling with a no-compromise double-wishbone design,” said Keith Goslin, Sales Tech Associate at Detroit Speed. “This system replaces the outdated factory suspension with modern geometry, increased strength, and race-proven adjustability, delivering premium fit, finish, and performance.”

Installation will require fabrication, but you’ll then enjoy a system that feels like it belongs on the car, because it was engineered that way from the beginning.

“When it comes to SLA suspensions, there’s a few on the market, but we do ours a little bit different,” stated Goslin. “Some out there use a shorter upper control arm and that’s not conducive for good geometry. You want as long as an arm as you can, so that’s why ours is a little bit different. The upper arm mount gets welded into the frame rail to give you that upper control arm length.

“Our exclusive frame rail insert optimizes camber gain and roll center height, significantly improving front-end stability.
The tubular upper and lower control arms reduce deflection, providing precise suspension movement and sharper handling   response. Our SLA system is designed with intention. Instead of just swapping struts for control arms, we reengineered how the
suspension should perform under real driving conditions. With forged aluminum uprights, C7 Corvette-based hub packs, and a geometry layout refined through testing, the result is a front end that delivers the feedback, grip, and consistency that serious
drivers demand,” he added.

There’s a lot of load bearing on that upper shock tower with the stock setup. That’s older technology and it’s worked for a while, but with that you’re just on a lower control arm and you’re limited on caster and camber adjustment. There’s only so much caster and camber you can achieve with that upper strut mount,” Goslin explained.

“With our Detroit Speed Front Suspension Speed Kit 2 [designed as a bolt-in kit], we fix that with an adjustable caster/camber plate, but you’re still limited versus how you can do it with an actual upper control arm that’s going to control that caster and camber properly. With our SLA you get the full effect,” he added.

Additionally, when you get into heavy cornering loads it’s necessary to make further modifications when the MacPherson strut is used.

“You must reinforce the shock tower braces and things like that to limit flexing in the unibody chassis. If not, you’ll get a lot of deflection because ’80s and ’90s cars are made of beer cans — specially on a hatchback where you lose that that reinforcement structure across the base of the C-pillar, so there will be tortional twist.”

Tighten Up The Ship

Detroit Speed also offers a bevy of frame connector and chassis-stiffening kits to add strength to any Fox Mustang and/or most Fox vehicles. And the system supports future
modifications quite well.

“There is some welding required,” Goslin stated. “The upper control arm mount gets cut into the factory frame rail and that gets welded in place. It’ll give you a little bit more wheel tire clearance especially when you do it with our front Fender Apron Panel kit.
Depending on your situation, like where you’re racing, you’re going to induce negative camber no matter what, whether it’s an SLA or whether it’s a factory-type suspension. You’re going to want to induce that negative camber like a half a degree at ride height. But in a race situation, depending on the track, it could be anywhere from 1.5 to 2.5 degrees of negative camber. With the SLA, you’ll be able to add a little bit more than with a strut-type set up. Both with our Speed kit we have the caster/camber plate that we base off our Aluma Frame with our Star Line set up to give you more accuracy, but you’re still limited because of the slots that are in that factory mounting point. Those slots are maybe what an inch and length if not, 3/4 of an inch so you’re limited.”

To complement the front, Goslin recommended adding the Detroit Speed QuadraLink Rear Suspension kit. “It’s a coilover conversion kit right along with our sway bar then our track bar kit and our upper lower swivel links. You can also add in the Excel Brace kit which stiffens the upper link pocket, and our subframe connectors stiffen up the lower torque boxes as well.”

Detroit Speed offers a Fender Apron kit to clean up the Fox engine bay. DSE also has a variety of components to improve the looks and handling of Fox body vehicles.

“For a street guy, the SLA set up still gives you more accurate steering. Your rack bolts right in and you can use the stock K-member or a tubular version that keeps the original lower control arm geometry and mounting points. Then, you would
use your rack and outer tire rods. If you’ve ever driven a stock or slightly modified Fox in any aggressive handling situation, you know they are excessively loose,” he added. “They can be constantly tail happy and if you got in a corner hard enough it felt like the rear shifting under the car. It’s a similar thing in the front. Sometimes it goes neutral, sometimes it will push it, sometimes it’s loose in the tail. They are just kind of sloppy, and you could feel the deflection in the suspension and in the chassis parts on the factory type setup. With our setup it’s tight and flat. There is no looseness or anything.”

Detroit Speed offers a complete line of JRi aluminum coilover shocks for precision damping control. The set you pick will likely be based on budget and performance goals. The kit allows clearance for up to 275/35R18 tires while maintaining full steering lock.

Fitment Notes

• Fabrication required
• Optimized for factory 1987-1993 V8 K-members and aftermarket K-members
• Requires S550 Mustang (2015-2024) brake system
• Hub utilizes 5×4.5-inch wheel bolt circle, 2.78-inch pilot diameter