The Ultimate Mustang Suspension Guide - Everything You Need to Know

Camber is how the tire leans when viewed from the front of the car. The top of the tire can either lean in slightly, lean out slightly, or be perfectly vertical. At first, you might think that a perfectly vertical tire orientation is preferred, but that is not always going to be the case. A little negative camber can enhance a vehicle's cornering ability, allowing the outside tire to grip better in the corner, as the lower side of the tire will have a tendency to try and roll under as it turns. Positive camber is when the upper end of the tire leans out further than the bottom. Positive camber should be avoided, as it is detrimental to handling in nearly all cases. Zero camber is when the wheel and tire are perfectly straight, vertically.

As you lower your car, you also change the camber angle of the front wheels. If this is left out of spec, it can dramatically affect tire wear. In some cases, all that’s needed is a trip to the alignment shop. The larger amount of lowering involved, however, the more you may find yourself needing to enlist the help of camber plates for your front shock towers.

Caster describes the relationship between the steering axis and a true vertical position. In the case of the Mustang, the steering axis is the strut. A higher caster angle gives a car more stability at higher speeds, although at slower speeds, the steering will feel heavier. Caster can also enhance the camber angle as the wheel is turned, giving you more grip in a turn.

Toe angle refers to the relationship of the tires to one another, in regards to the direction they are pointed. Toe-in has the two tires pointing slightly together, while toe-out has them pointing slightly apart. A slight amount of toe-in helps higher speed stability, as the wheels will toe-out slightly as speeds increase.

An alignment refers to a procedure that alters the camber, caster, and toe angle to make sure the vehicle is set correctly. What is considered "correct" can refer to factory specs, or, in the event of a race-prepped car, some more aggressive settings intended to help the suspension performance. Camber and caster are set at the front shock tower or the strut itself. Toe is adjusted via the steering tie rods. While you can alter the alignment at home, it's best to take it to a shop that has the capability to accurately measure your front suspension adjustments. 

Major Mustang Suspension Components: A vehicle's suspension involves several components, each serving an important task. As a whole, they all work together, giving the vehicle its handling characteristics. Knowing what these components are is the primary step to understanding how the suspension works.

The Mustang uses a chassis with two main components, the front and rear subframe. While the two sections are connected by the floor pan, this is nothing more than sheet metal. The actual frame rails are not connected. While the rest of the car's body provides some rigidity, there can be unwanted flex when the chassis of the car is stressed. This stress can be a result of hard cornering or dragstrip launches. The solution for this is simple, and can be found in the form of subframe connectors which will tie the front and rear subframes together, thus stiffening the chassis.

• Bolt-on subframe connectors offer easier installation
• Welded connectors provide more stiffness than bolt-ons
• Strut tower braces also help reduce body flex in a different way than subframe connectors
• Some strut braces have the clearance for supercharger engines
• Rear shock braces are a minor upgrade, but stilll reduce flex. Usually requires welding
• Torque box braces dampen the force of hard launches
• A full roll cage offers the most riggidty. Depending on your end goals, this might also be the best option

There are a variety of suspension components controlling how your Mustang handles:

• Ball joints
• Bump steer kits 
• Control arms (Not applicable to S550 Mustangs)
• Sway bars
• Shocks and struts
• Springs
• Strut and shock tower braces
• Panhard bar (Not applicable to S550 Mustangs)
• Vertical links (S550 only)
• Toe rods (S550 only)
• IRS bushings (S550 only)

With all of the above coming standard on your Mustang, there are a good bit of aftermarket add-ons that either replace and existing component or are a completely new addition. These include:

• Air lift suspension kits (replaces shocks, struts, and springs)
• Coil over kits (replaces shocks, struts, and springs)
• Watts Link kits (replaces panhard bars)
• Caster camber kits

The late model Mustang's front suspension tends to be a bit more complicated than the rear, due to the steering rack and associated components. Up until 2004, struts and springs were mounted separately with the spring closer to the engine. Beginning in 2005, the springs were mounted over the front struts up in the top of the wheel well. The wheel’s spindle is mounted to the control arm, providing a point to mount the wheel and tire. A sway bar is used to connect the two control arms together, and is used to help control body roll.

Up until 2004, the late model Mustang used a four-link rear suspension. Two upper and two lower control arms hold the rear axle in place, giving the suspension its four-link moniker. Springs are used to support the rear of the car, above the axle, with separate shocks installed to control the dampening. Depending upon whether the Mustang is a V6 or V8, it has a 7.5 or an 8.8 inch rear end. The 7.5 uses an open differential while the GT's 8.8 inch rear end uses Ford's Traction-Lok differential. The 8.8 inch rear end was also equipped with quad-shocks during these years which help dampen the axle and reduce wheel hop. A sway bar is installed on both versions of the rear end to help control body roll.

The rear suspension underwent a significant change in the 2005 model year in the form of how the rear axle is positioned under the car. The four-link suspension setup was nixed in favor of a three-link panhard bar setup. The change to this arrangement was a tradeoff between a full independent rear suspension and a solid axle. An independent rear suspension would have added a substantial cost to the initial price of the Mustang. In addition, many Mustang enthusiasts prefer a solid axle anyway, as it's more suitable for dragstrip duties. The panhard bar setup still allows the Mustang to keep the solid axle, while providing cornering ability improvements that suit most owners better than previous generations of the Mustang.

There are a few common problems that impact all stock Mustang owners and their handling. Wheel hop off the line, where your rear axle bounces up and down as it struggles to get traction is a common issue on all Mustangs, especially the S550 models. Mustangs can also suffer from body roll off the line and going around turns due to lack of stiffening and support throughout the frame. Any gen Mustang can feel somewhat floaty and high up due to the stock spring ratios, which are great for daily driving and absorbing bumps and pot holes, but awful for handling and curbside appeal.

Non-IRS equipped Mustangs (basically everything prior to 2015) can have issues in turns due to the solid rear axle (SRA) design that gets ‘twitchy’ when it hits a bump or uneven pavement. S550 Mustangs specifically can have trouble getting off the line and launching due to weak IRS bushings that have trouble keep the rear axles planted.

Ball joints eliminate the sloppy steering feel Mustangs can sometime suffer from. When ball joints get warn out, they clunk and squeak when going through a turn while feeling incredibly loose. A great time to upgrade them is when the stock ones wear out, giving you not only revitalized steering and handling, but overall improved performance. 

Bumpsteer is a change in toe angle caused by the suspension moving up or down. Bumpsteer is built into the geometry of the Mustang’s suspension and steering system and has nothing to do with turning the steering wheel. The effect of bumpsteer is for the wheel to toe-in or toe-out when the suspension moves up or down. This toe change or "steering" occurs any time the suspension moves due to the tie rods traveling at a different rate than the control arms. Whether it is from body roll, brake-dive, or hitting a bump in the road, bumpsteer is undesirable because the suspension is steering the car instead of the driver.

When bumpsteer occurs, the front of the tires will change slightly in their relation to one another. This is due to the tie rods traveling at a different rate than the control arms. There will always be some bumpsteer in a Mustang's suspension, but this can be exaggerated if the car is lowered. The use of a bumpsteer kit will help eliminate this, by repositioning the tie rod ends and realigning and correcting the geometry of your Mustang's front end suspension.

Control arms are one of the biggest and most popular Mustang suspension modifications as they help to keep the wheels planted. There are rear and front control arms, along with upper and lower control arms. Rear lower control arms are the major key to hooking up and getting off the line as they keep your tires firmly planted. 

In addition to quicker launches, control arms also offer better stopping performance by keeping your tires on the road rather than hopping to a stop. Stock control arms were not designed to withstand hard launches and performance uses let alone the huge power upgrades that many Mustang enthusiasts perform. They are often constructed of U-shaped bent steel that can flex under pressure such as accelerating from a stop. Upgraded control arms often come in cylindrical or box shaped reinforced steel with polyurethane bushings maximizing smoothness while not sacrificing strength. Some control arms even offer a greasing point to ensure constant lubrication.

The big question you’ll have to ask yourself when buying control arms is if you want adjustable or non-adjustable control arms. Adjustable control arms allow you to dial in and fine-tune the suspension to your exact liking. Non-adjustable control arms are like a one size fits all. Instead of using rear control arms, S550 Mustangs use vertical links to keep the rear wheels on the pavement and hooking up.

The front control arms are generally something that gets replaced on a vehicle that will see more serious track duty. Replacement front control arms can offer adjustability of roll center and bumpsteer. In the case of most Mustang owners, replacement of the rear control arms is a very useful upgrade. Replacement upper and lower rear control arms allow you to bring the vehicle back into spec after lowering it. 

2005 Mustang Note: When lowering your Mustang, the three-link suspension can negatively affect the pinion angle. An incorrect pinion angle can cause undesired stress on the universal joints, excessive drivetrain noise or vibration, or even possible contact between the underside of the car and the rear axle. Upper control arms combat this.

Mustang sway bars eliminate body roll and keep your Mustang feeling stiff in the corners. As the body leans, grip is transferred from one side of the car to the other. While some weight transfer can be beneficial, too much can adversely affect handling. Keeping the car flatter in turns provides more even grip at the tires on both sides of the car, which helps to neutralize excessive oversteer. A car that leans too much will apply more traction to the wheels receiving more of the weight. This can unload the differential, and causes oversteer. 

Your Mustang has two sway bars, one in the front and one in the back. The factory sway bars are non-adjustable. However, you can buy adjustable and non-adjustable aftermarket upgrade options. Sway bars are an excellent complement to a set of control arms in terms of overall handling prowess. Drag racers often remove their front sway bar to get improved weight transfer while dropping a few pounds off of the nose as well. 

The front sway bar connects to end links which then connect to the control arms and the chassis itself by mounting with rubber or urethane bushings. The rear sway bar connects to each of the lower control arms. On a Mustang, the rear sway bar should always be a smaller diameter since the car is rear wheel drive. A bigger sway bar in the front increases lateral and motive traction in the rear and in cases where the rear sway bar is the bigger of the two this causes an increase in traction of the front tires.

Shocks and struts are what holds your Mustang up and help it to turn in. The shocks are in the rear and the struts are in the front of your Mustang, and they are encased by your Mustang’s springs. When you lower your Mustang with a set of springs, you will want to consider upgrading the shocks and struts as well to maintain a balance throughout the vehicle.

Going to a set of aftermarket shocks and struts will make you feel those little bumps in the road a bit more, but they will also drastically improve your handling and weight transfer throughout the vehicle.

Shocks and struts are typically matched to a certain set of springs. As spring rates and ride heights change, so does the dampening needed from the shocks and struts. The springs' job is to support the vehicle while the shocks and struts control the rebound of the spring, preventing the ride from being too bouncy and handling poorly. So the strength of the spring will dictate the action required from the shocks and struts. You can also change the shocks and struts while keeping the same springs, to control how the suspension reacts and handles, should you desire to have either a slightly looser or firmer feel.

Replacement springs serve two main purposes. They are: to alter the vehicle's handling and to lower its stance. When replacing your springs, it's wise to closely examine your needs. Are you looking to improve handling, and if so, by how much? If you want to lower your Mustang, how far do you want to go? The spring options and characteristics are nearly infinite, so properly planning a spring swap is important.

Mustang springs go around the shocks and struts and help to control your vehicle, specifically when launching off the line or in a turn. Springs have progressive rates that take an increasing amount of force to compress the spring the same amount of height and there are linear spring rates that require just as much force to compress it the first inch as it would the third inch. Progressive spring rates are considered to be better for daily driving and cornering, while linear spring rates are better for drag racing.

Springs are the easiest way to lower your Mustang, providing anywhere from a .5”-2” of static lowering. When you lower your Mustang with springs, you will want to also upgrade the bump steer kit and the shocks and struts, while considering caster camber plates. Springs are also a nice appearance modification as they help to eliminate that horrible factory wheel gap, dropping your Mustang and lowering the center of gravity for increased nimbleness in the turns. 

You should make sure the spring is suitable for your application, as whether the car is a coupe, convertible, V6, or V8, will make a difference. Springs will be tuned for a certain weight, and will be intended for a certain type(s) of car.

The Mustang has a natural tendency to sit a little higher in the rear than in the front. So some owners may find themselves simply wanting to level the car instead of lowering it. To achieve this, you’ll find a few kits on the market specifically for this task. Roush is one of the more commonly used sources for this sort of spring kit. 

The lower the car, the more important the rate becomes. This is because you have less suspension travel to abosrb impacts. With the appropriate spring however, you can lessen the stiff ride and save yourself multiple dentist trips. Your goals should also take into account what spring rate is ideal for your situation.

Ultra-Lite: The reasons you wish to change your springs also weigh into the equation. While most people simply want to lower their car for appearance reasons, there are some who are doing it from more of a performance standpoint. If you fall into the former category, you may want to use a lighter spring to keep the ride quality of your Mustang as close to what it was before. Springs in this category are referred to as Ultra-Lite Springs.

Sport: If you’re looking to tighten up the feel of the suspension, you may want to investigate Sport Springs. Sport Springs are a little stiffer than stock, but offer a good compromise between stock and some added performance. They are a middle of the road option for those looking to keep the stock ride, but aren’t going to do any serious track racing. Keep in mind I’m referring to road racing, not drag racing. We’ll discuss drag racing in a moment.

Competition: Competition spring rates throw ride quality out of the equation in favor of handling and performance. These types of springs are typically used for cars that see a large amount of track time. While they can be used on the street, ride quality will definitely be much harsher than with the stock springs. They will also be harsher than springs in the other categories.

Drag-Springs: Drag racing springs are very different from the other types, but just as with the competition springs they are best suited for track use. The difference when compared to the competition springs is that drag-springs allow the suspension to have a much fuller range of movement. This is due to a softer spring rate, and also has a side effect of cornering ability suffering. The car will launch at the starting line with a little more authority, however, since the spring rate allows the weight of the car to transfer to the rear wheels better than with other springs. This assists the car in hooking up and getting the power to the ground.

Standard: Standard springs have a spring rate that rises in a linear manner. While the spring rate can increase as the spring is compressed, it rises in a predictable manner. For example, at the first inch of travel it may be a 50 lb. rate, while at 2 inches it will be 100 lbs., and at 3 inches a 200 lb. rate. While the rate will vary from spring to spring, the increase in rate is predictable. Standard springs are most often used for drag and road racing applications, as their linear rates allow the driver to more accurately predict how the suspension will react.

Progressive: Progressive springs operate in a much different manner than standard springs. The rise in spring is not linear, allowing for a softer spring rate in the early stages of travel, but a much stiffer rate as the spring is compressed further. So while the first inch of travel may be at a 50 lb. rate, the second inch of travel may step up to a 200lb rate, and continue to increase from that point. Progressive springs find more of a use on the street. The fact that they can have a much softer initial rate before they get stiffer makes them ideal for maintaining ride quality while still preventing the car’s suspension from travelling too far when necessary.

To put it simply: NEVER modify your stock OEM springs and other suspension components by cutting it up. This will very negatively affect your performance and handling. Cutting springs to lower the vehicle will unpredictably affect the spring rate and could cause damage to your vehicle. If you are looking to lower your Mustang, do it properly with the right parts that have been tested and vetted with rigorous R&D.

The front strut/shock towers are another point on the Mustang chassis that can benefit from some additional strengthening. These towers serve as the mounting point for the struts, and therefore they are the recipients of a great deal of stress. In fact, with the proper tools, you can even measure small changes in the relationship of the shock towers to one another when the vehicle is jacked up as opposed to resting on the ground. Knowing that, one can easily see why hard cornering could cause chassis flex in this area.

To combat this, you can install a brace that will tie the two towers to one another. This reduces flex, thanks to the tubular or bar-shaped section that's used for the main body of the brace. Different connectors may use either two, or four of the bolts on each shock tower. The use of all four bolts provides more rigidity, but visiting the alignment shop afterwards is a good idea, as removing all four bolts for installation can alter your vehicle's alignment.

A shock tower base goes from the top of the driver’s side shock to the passenger’s side with a piece of metal to brace your Mustang and provide increased frame rigidity. Strut tower braces, the more common of the two, do the same thing, but in your engine bay going from strut to strut. Adding a strut or shock tower brace to your Mustang will help it feel much more planted when turning, reducing the amount of body roll and chassis flex that the platform is prone to. A shock and strut tower brace is highly recommended if you autocross or drift your Mustang because these are the situations where you will notice a difference the most due to the increased speed and subsequent flexing.

There are a multitude of shock/strut braces on the market. If you're trying to clear more than just the engine. However, the selection will narrow somewhat, and choosing the proper one is much more critical. While the following suggestions are not your only options, they may help if you're looking at purchasing a strut tower brace.

• 1999-2004 Mustang: Steeda Strut Tower Brace (American Muscle Part # 16107)
• 2003-2004 Mustang Cobra: Agent 47 Strut Tower Brace (American Muscle Part # 30201)
• 2005 Mustang: Agent 47 Double Barrel Max Clearance Strut Tower Brace (American Muscle Part # 30200)

Just like the front strut tower brace, a rear shock tower brace can reduce unwanted flex as well. The rear shock towers are generally not under as much stress as the front, but if you're looking to continue strengthening your Mustangs chassis, a rear shock tower brace will certainly do it. There are fewer options for rear shock tower braces, but still plenty to choose from. Most rear shock tower braces will also require some welding as well, which makes installation a little more complicated than a simple bolt-on affair.

Panhard bars are only found on Mustang up until 2015 as they are needed on solid rear axle (SRA) cars. Panhard bars work to keep your Mustangs rear axle centered, reducing lateral movement. Panhard bars work to correct rear steer and allow your SRA equipped Mustang to handle more consistently and predictably while cornering. 

Panhard bars are a required upgrade when you lower your Mustang as you will need to adjust the rear axle. Panhard bars are available in both adjustable and non-adjustable varieties, with adjustable bars being more ideal for lowered cars and competitive builds. 

Another alternative to panhard bars is a watts link setup that will replace the panhard bar, taking on all of the same responsibilities while also helping to prevent vertical movement. Watts link suspension systems help to make a SRA equipped Mustang feel more like an IRS equipped one.

From the factory, Ford uses rubber bushings throughout the Mustang's suspension. While rubber bushings aren't the best option from a performance standpoint, they do help keep the cost down and provide a smoother ride by controlling what's called NVH (Noise, Vibration, and Harshness). Keep in mind that a large number of Mustang owners never even really modify their car, so Ford's use of rubber bushings makes sense in that regard. If you're reading this, however, you're not one of those people! You're looking to improve your car in the way that suits you best.

If handling is a priority, then replacement bushings are the answer. While there are a few different types of materials available, the most commonly used option is polyurethane. Polyurethane bushings will provide a much firmer feel than the factory rubber pieces and, when properly maintained, will outlast the stock components. Factory or replacement rubber bushings will tend to dry out and crack, due to their larger amount of flexibility and the natural properties of rubber as a material.  

S550 IRS bushings are crucial for 2015 Mustang owners who want to drag race their Mustang as they take a lot of slack/slop and play out of the suspension. The stock bushings can allow rear sub frame movement that can absolutely ruin a quarter mile time. IRS bushing help the S550’s rear feel more solid and planted, especially when taking off from the line.

Vertical links are essentially rear lower control arms for IRS cars. Due to the design of the IRS system, traditional control arms don’t fit/have the same impact, so instead vertical links are used to keep the rear wheels planted. They function almost identically to lower control arms and a huge component to eliminating wheel hop in an S550 Mustang.

Toe rods work like a bump steer kit and help to keep the toe angle of your rear wheels within spec. Toe rods optimize and improve traction, especially off of the line, and provide an overall more balanced ride.

An upgrade that was made popular by S197 Mustangs and has since spread out to other gens is replacing the main bits of the suspension with an air lift suspension kit. Air suspension kits remove the shocks, struts, and springs, replacing them with a pneumatically controlled air bag and air spring. These kits allow for extreme lowering (up to 5”) and can raise the suspension up to 1” over stock. Air lift kits are typically used on more show cars, however they do maintain solid performance in the turns and off the line.

A bonus of air ride suspension is you can adjust for awkward driveways and parking lots. A static lowered Mustang may be an unrealistic upgrade depending on the roads your travel. When thinking about air ride vs. lowering springs, you should think about places you visit on a regular basis such as stores and your job. Other things to consider are routine maintenance. Can you get a jack under the car to lift it when changing your oil, or will you also need to get some ramps to raise the car enough to use the jack? After considering all the potential issues, you may find that you want to lower a car a little less you had originally intended or that an air ride setup is more appropriate.

Mustang coil over kits replace the stock shocks, struts, and springs with one all-encompassing unit that provides a static drop height. Some of these kits allow you to preset/predetermine how low you’d like to go, but the average drop you can expect from a coil over kit is anywhere from 1” to 2.5” inches. Coil over kits are not necessarily ideal for daily drivers as they will absorb bumps and potholes less efficiently, but they will provide arguably the best handling setup when compared to your other options.

Although the top of your front shock towers allow you to adjust the vehicle's camber, if you're looking to enhance handling you'll likely find that the adjustability allowed is minimal. This is especially true with lowered cars, in which case, there may simply not be enough adjustability offered at all. I've seen many factory stock Mustangs prior to 2005 that have alignment issues at the factory height as the lack of adjustability can be that limited.

This is where caster/camber plates come in. Picking up where the factory adjustments options fall short, they give you a much greater range of adjustability for camber, while also adding the option to adjust your caster angle. So whether you're looking to enhance your vehicle's cornering ability, or bring it back into spec, a set of caster/camber plates is definitely a worthwhile investment. Caster camber plates help to adjust the caster and camber of your front wheels, helping to improve the turning radius and balance of the front end. Caster camber plates are a relatively inexpensive upgrade that provide a lot of bang for their buck and are installed atop of your Mustang’s struts for quick and easy adjustability.

Mustang subframe connectors help to make your ride more rigid and stiff, cutting out and down on body roll in corners and off the line. Subframe connectors can come in a variety of style from 3-point bars to x-braces in the rear seat. Additional chassis bracing helps to control and even out the weight transfer of your Mustang in turns. 

Bolt-on subframe connectors are the easiest to install. They simply bolt into place between the frame rails, although some connectors may require additional holes to be drilled. Once installed, the connectors connect the front and rear subframes into a single cohesive unit. For additional strength, you can additionally weld the bolt-on subframe connectors as well, strengthening them even further. Over time, the bolts can loosen or even shift their hold, as the car's subframes try to twist apart from one another. Welding helps to prevent this.

The best options, when it comes to subframe connectors, are ones that weld into place. These subframe connectors offer improved strength, because they do not rely on bolts to secure them to the front and rear subframes. Since the average person doesn't have the capability of welding them in their garage, installation will likely involve a trip to a shop that will weld them into place for you.

Due to the lack of a true roof in a convertible, the uni-body chassis is weaker than it would be with a coupe. So for most year models of the Mustang, Ford equipped them with subframe connectors from the factory. These subframe connectors are bolted into place, and helped make up for the lack of the roof's ability to help strengthen the chassis frame.

Connecting the subframes of the Mustang with subframe connectors aren't going to address all the weak spots in the chassis. While it will help, there's still another crucial area to address for drag racers launching at higher RPM's. That area is the rear torque boxes. This area catches the brunt of a hard launch, receiving a lot of stress from the axle, especially if the rest of the chassis is stiffened up already.

There are several options to choose from in regards to torque box braces. Some are smaller braces that weld in place, while others are larger and can tie the torque box area into the frame rail. You can choose between bolt-on options and those that are intended to be welded. As with the subframe connectors, welding the braces will yield an advantage when it comes to strength.

If you want to look into the ultimate way to stiffen up your Mustang, as well as provide a safer place for the driver, look towards a roll bar or roll cage. You can get a simple 4-point bar for the rear of the Mustang, or elect to get a full cage to offer substantial protection and chassis stiffening. As with many other suspension components, you can get roll cages that bolt in place, or that require welding. Depending upon how fast your car is, some tracks may require a certain type of roll bar or roll cage. So if you have dragstrip goals in mind, plan ahead. It's easier to do it right the first time, than to do it multiple times. Note that for convertibles, a light bar does not fall into this category. It is merely a cosmetic feature.