Learn everything you need to know about your factory Fox Body suspension as well as how to upgrade your suspension system for different driving applications.
The Fox Body Mustang is a car enthusiast's dream as just about every part of this iconic Pony car can be modified to build a vehicle specific for just about every motorsport. One of the most popular areas that Fox owners tend to upgrade is the suspension. The suspension on a Fox Body should be built to fit the specific goals of the vehicle, so there are several routes that you can take. Today, we take a closer look at the factory suspension system on a 1979-1993 Mustang, what the weak points are, and what components you can use to upgrade your suspension.
Understanding Fox Body Suspension
The Fox Body Mustang, and all 1979-2004 Mustangs, have a modified MacPherson strut front suspension and a four-link suspension in the rear. Let’s look closer at the OEM suspension system setups before diving into the weak points and commonly upgraded components.
Fox Body Front Suspension
The modified MacPherson strut front suspension found on the front end of the Fox Body is made up of a k-member, lower a-arms, struts, and coil springs. The coil springs on Fox Body Mustangs are nestled in between the lower a-arms and the factory k-member. Unlike a traditional MacPherson strut setup, the springs are not mounted on the strut assembly.
Fox Body Rear Suspension
In the rear of a Fox Body, you will find an 8.8" solid axle rear end, 2 upper control arms, 2 lower control arms, and coil springs. The coil springs sit between the frame of the car and the lower control arms. Like the front suspension, the coil springs are mounted separately from the rear shocks.
In the middle of 1984, Ford added a “Quad Shock” to reduce wheel hop caused by compliant bushings and the axle winding up. These quad shocks are mounted from the car's frame to the axle tube quad shock brackets.
Common Weak Points On Fox Body Mustang Suspension
When Ford built the Fox Body Mustang, they knew that it would be a common visitor of drag strips across the US, but these cars were built with the everyday consumer in mind. That means that Noise, Vibration, and Harshness (NVH), were taken into consideration, offering a smooth and comfortable ride quality. This was great for daily driving, but once you started adding some horsepower, sticky tires, and high-rev clutch drops, the factory Fox suspension showed its weak points. Let’s take a look at the most common weak points of the Fox Body suspension.
Bushings
The suspension bushings on a Fox Body are made with comfort in mind. They are not built to take the abuse of drag racing or road racing. Not to mention, with these cars being on the road for decades, the bushings have most likely seen better days. Many enthusiasts switch to high-quality polyurethane bushings, such as those from Prothane, for a stronger, more durable bushing, that trades off in the NVH department.
Rear Control Arms
Factory controls arms on 1979-1993 Mustangs were made from stamped steel in a “U” shaped pattern with rubber bushings. Not only did the bushing deteriorate with constant hard driving, but the control arms themselves could give “flex” resulting in less power being transferred to the ground. Upgrading to a boxed or tubular rear control arm is a great way to strengthen the rear end of your Fox’s suspension. Aftermarket rear control arms often negate the need for the quad-shock.
Lack Of Body Bracing
Due to the unibody frame construction of the Fox Body, launching these Mustangs at the track could cause the frame to twist. This could be easily resolved with the addition of body bracing components such as strut tower braces, lower chassis bracing, subframe connectors, and roll bars.
Torque Boxes
The torque box in a Fox Body is an area that becomes damaged over time due to the axle loading on launch and the control arms basically trying to pull themselves away from the chassis during hard accelerations. The lower torque boxes are located at the rear of the pinch welds and in front of the rear lower control arms, while the upper torque boxes are located directly above the mounting location of the upper control arms to the chassis. At LMR.com, we understand that this weak point needs to be braced, which is why we developed our SVE Torque Box Reinforcement Kit to help remedy this issue or prevent damage in the future.
Choosing The Right Upgrades
When adding suspension upgrades to a Fox Body Mustang, there are a few different things you want to take into consideration such as budget, intended use, and the customization level of the vehicle. Let’s take a closer look at each of these factors to give you a better idea when shopping for Fox Body suspension.
Factors To Consider Before Upgrading
Budget
One of the biggest factors when it comes to upgrading your Fox Body suspension is the budget. You will want to determine how much you want to spend and what possible supplemental parts you may need as well. For instance, if you add lowering springs, you are going to need to add caster camber plates to correct your suspension geometry. It is also recommended to upgrade your factory shocks when installing lowering springs as well.
There are also different budget levels when it comes to specific components as well. You can find budget-friendly solutions that are more entry-level modifications or you can go all out with race-specific components that will be on the higher end of the pricing spectrum.
The budget you have will also determine which brands you will want to shop for. We offer great Fox Body suspension upgrade components from top brands such as SVE, Maximum Motorsports, Eibach, BBK, and much more.
Intended Use
Intended use is the most important factor as you will want to build your suspension for the sole purpose of the performance you want out of your Fox. With such a wide variety of suspension components available for the 1979-1993 Ford Mustang, you have plenty to choose from to dial it in for daily driving, road racing, drag racing, auto-x, or drifting. We touch on the recommended upgrades for different goals below.
Customization Level
Lastly, customization level will need to be considered as some suspension components are simple bolt-ons while some require permanent modification to your vehicle. While this usually is reserved for more serious modification, some items such as weld-in subframe connectors and torque box reinforcements will require you to weld the component onto your vehicle. For those who as simply daily driving or seeing light track duty, common bolt-ons will usually suffice without serious modifications to your vehicle.
Recommended Upgrades For Different Goals
While upgrading your Fox Body suspension is great for restoring and getting better performance for your Fox, the upgrades you choose should reflect the overall goals of the car. Whether you are just daily driving your Fox or plan on building a full-on race car, it is important to pick your suspension components wisely.
Daily Driving Improvements
If you plan on using your Fox Body for mainly daily driving, then you will want to purchase parts that are a slight upgrade from factory parts to keep Noise, Vibration, and Harness down, which is commonly increased when adding more serious suspension components.
Lowering Springs
Lowering springs are a great first upgrade for those who want to get better handling and give their Fox a new look. Lowering springs lower your vehicle anywhere from .5” to 1.5”, depending on the kit you choose. The lower you go, the more you will experience NVH without upgrading other components such as shocks and struts. Our SVE lowering springs are a great way to lower your Fox Body, get better handling, and save a few extra dollars when compared to other brands.
Caster/Camber Plates
When adding lowering springs, you will need to consider caster camber plates to correct the suspension geometry. These Fox Body caster camber plates mount on your strut towers to the top of the front struts to adjust the caster and camber. Without caster/camber plates, you risk wearing your tires faster and experiencing erratic handling characteristics. We offer great budget friendly options such as the SVE Caster Camber plates, or you can opt for the Maximum Motorsports caster camber plates for a little more money.
Shocks/Struts
A simple upgraded aftermarket shock and strut are ideal for most Fox owners who will be driving their vehicles daily. For normal driving conditions, these struts and shocks will allow you to get a boost in suspension performance over worn-out factory components while allowing you to run lowering springs and participate in more spirited driving.
Bumpsteer Kit
When you lower your Mustang, it throws off the factory geometry of your suspension. This leads to uneven tire wear, unpredictable steering, and bump steer. Bump steer refers to the change in toe in / toe out as the suspension moves up or down. . When the suspension geometry is off, when you hit a bump, your wheels may get pushed to the left or right. A bump steer kit helps to eliminate this by replacing your factory outer tie rod with heavy-duty, spherical rod ends that are adjustable.
Control Arms
When it comes to upgrading control arms, there are a few different routes you can take. For daily driving, we suggest upgrading to our Factory Style control arms to restore your suspension with upgraded components or switching to tubular control arms if you plan on doing some weekend drag racing. The common fail point in factory control arms is the bushings, so choosing control arms with urethane bushings is always a good upgrade for performance applications.
Chassis Stiffening
Similar to sway bars, various chassis stiffening components can be added to make your daily driver handle better. Common chassis stiffening upgrades for entry-level Fox owners are subframe connectors, strut tower braces, and torque box reinforcements. The best part about these upgrades is that they can be used in various applications if you choose to go a different route later down the road.
Road Racing/Auto X Performance Enhancements
For Fox Enthusiasts who are looking to build a road racing/auto x Mustang, there are a few specific upgrades you will want to look into. The above-mentioned daily driving mods are a great starting point, but the following parts will help dial in your suspension with adjustable components.
Coilovers
One of the most popular upgrades for Fox Body owners who are looking to road race or auto-x their Mustang is a coil-over kit. Front coil-over conversion kits for Fox Body Mustangs replace your modified MacPherson strut setup with an adjustable coil-on-strut setup. The rear coil-over setups for the Fox Body can be purchased as a coil-on-shock setup or a “divorced” setup where the spring and strut are separate.
Coil-over kits are designed to allow you to fine-tune your suspension by adjusting the ride height with a Spanner wrench. Coil-over kits are available at different spring rates to give you more options for your car’s intended purpose.
Sway Bars
Anyone who has driven a Fox Body understands the large amount of body roll these vehicles have. Over the years, sway bar bushings have deteriorated, contributing to even more body roll and poor cornering capabilities. Upgrading your factory front and rear sway bar on a Fox Body is a great way to tighten up your suspension for a more enjoyable and responsive driving experience. When road racing and doing auto-x events, you will want great cornering characteristics to ensure you are unloading and offloading the suspension effectively.
Panhard Bar
A Panhard bar eliminates the Fox Body's unstable and unpredictable behavior while cornering near its limit. This feeling is caused by the rear of the car steering itself without any input from the driver. Rear-end steering is caused by the sideways movement of the rear axle. In addition, the Mustang upper control arms are at about a 45-degree angle from the direction of the cornering load. Some binding in these arms is induced during cornering as one arm enters into compression and the other enters into tension. Maximum Motorsports is one of the leading providers of Fox Body panhard bars.
Drag Racing Setups
If you are more of a straight-line racer, the Fox Body Mustang was a perfect platform to build a drag car out of. With its light weight and aftermarket support, the Fox Body has been one of the most popular vehicles at drag strips around the country since the early 1980s. To get your Fox launching perfectly off the line, you are going to need a suspension setup built for drag racing.
Drag Springs
When drag racing, the goal is to get your vehicle down the track as quickly as possible. The first 60 feet is crucial, so launching off the start line requires specific drag components to get dialed in. Replacing your rear springs with drag springs is a great way to get lower ETs and quicker 60’ times. These springs are designed with specific materials and improved geometry to help with weight transfer.
Control Arms
While control arms are a great upgrade for any Fox owner looking to upgrade their suspension, they are essential for those who will be drag racing. Drag racing puts a tremendous amount of stress on your vehicle’s suspension components, especially your control arms. Factory control arms will twist, deteriorate, or become damaged with continuous launching at high RPMS and the use of drag radials/slicks. For drag-centric Fox Body builds, we suggest tubular control arms with urethane or spherical bushings.
Drag/Adjustable Shocks & Struts
When it comes to shocks & struts for drag racing, adjustable components and coilovers are usually the route most drag racers take. Adjustable shocks and struts allow you to fine-tune your suspension to get the best performance on race day. Weight distribution is important when it comes to drag racing, so having a way to fine-tune the components responsible for transferring weight during launching is key.
Tubular K-Member Kits
The factory K-member, front control arms, and springs weigh in at around 80-100lbs, so switching to a tubular K-member and coilovers can be one of the most effective Fox Body weight reduction mods you can do. The OEM K-member is made from stamped steel and is bulky, taking up precious room in your engine bay. A tubular Fox Body K-member uses a tubular construction which saves weight and room in the front end of your Mustang.
Chassis Stiffening/Roll Cages
Chassis stiffening components are a great upgrade for all Fox Body Mustangs, no matter what the end goal is. However, in drag racing, they are critical in keeping your body/frame from flexing and enduring all of the available torque sent to the wheels. For drag racing, we suggest adding subframe connectors, torque box reinforcements, strut tower braces, and a roll cage if possible. These components will help tighten up your Fox Body and help reduce the flex of your vehicle when launching.
Common Fox Body Suspension Tech Guides
At LMR.com, we understand the need for wanting to do your own installs and suspension upgrades. That is why we have put together a great list of how-to guides to help walk you through your installs.
Now that we have looked at everything you need to know about the OEM Fox Body suspension, aftermarket Fox Body suspension upgrades, and a few installation tips to help you get them installed, you should be well-equipped to start upgrading your 1979-1993 Mustang.
At LMR.com, we are proud to offer just about any and everything you need to get your Fox Body suspension restored or upgraded for your specific goals. Our tech team is here to help assist you in your build and can help you find the best components for your needs. Shop our full selection of Fox Body suspension parts today!
About the Author
Tyler has written content for Late Model Restoration for nearly 8 years, producing over 300 articles. As an avid New Edge fan, Tyler has owned 4 2004 Mustangs and an 88 Convertible Fox Body. Read more...
