For the first time, there is a completely bolt-in 4-Link rear suspension solution for your Challenger and Charger Hellcat based vehicle. This system converts your Independent Rear Suspension (IRS) driveline components into a bulletproof 4-link offset live-axle set up that completely eliminates wheel hop and increases traction more than any other modern day sports car with an independent rear suspension on the road today.
Until now, live axle drivelines have not been able to fit into today’s modern vehicles that are designed for Independent Rear Suspensions (IRS) without extensive permanent modifications to your car that require cutting up the car significantly. What is even worse is the fact that cutting up a car and welding to that degree makes it almost impossible to ever change it back to stock if you wanted to sell the car down the road. This system is a completely bolt-in solution that requires zero cutting, welding, or any other evasive modifications to the car in any way. The car could be converted completely back to stock within a single day and no trace it had ever been done. This means that you could drastically improve the performance of your vehicle whether it be at a drag strip or a road course with ever worrying about voiding the vehicles warranty.
Like your IRS unit, the bolt-in 4-link has its own much stronger rear subframe that bolts directly in place of the stock rear subframe. We eliminate the weak rubber mounts so the rear cradle increases the strength and rigidity of not only the driveline, but also the chassis of your vehicle against torsional torque loads caused by the extremely high horsepower that today’s muscle cars are producing. You do not have to worry about excessive driveline noise, vibrations, or harshness because we have come up with a solution to control those typical annoying attributes of many of the other suspension upgrades on the market. We use high-durometer rubber bushings on the cradle side of the control arm links and a Stainless-Steel R-Joint with a Delrin Bushing on the other side for maximum articulation and control. You can have all the performance without the creaks, rattles, and groans of a race car!
Factory shock mounting locations allows the use of custom dual adjustable coil over shocks with customizable spring rates to be used for maximum control and suspension tunability. The axle tubes are notched for plenty of exhaust clearance, allowing you to use your factory cat-back exhaust or any aftermarket exhaust you choose. The heavy-duty rear sway bar features fully adjustable end likes that allows for perfectly straight launches at the dragstrip and minimal body roll on a road course.
The system retains factory wheel speed sensors, emergency brake components and brake caliper mounting locations so that every single one of your factory options and safety systems like traction control and ABS remain fully functional. Fully adjustable 4-link bar locations mean you can control the amount of anti-squat in the rear suspension which means you will experience harder launches that would be physically impossible with an independent rear suspension set up. This means the with minor adjustments, you can go from wheelie-level drag strip traction, to no-prep street action, to setting road course lap records, all with one suspension system. If you are not familiar with 4-link suspensions, then we will cover the basics so you can understand why and how this system is so beneficial.
Independent Rear Suspension (IRS) Benefits:
Almost all modern vehicles utilize an Independent Rear Suspension (IRS) for multiple reasons. Packaging, ride quality, noise and vibration suppression, ease of assembly on the assembly line and the perception of using “high technology” are the main factors for incorporating this style of suspension. Now, Independent Rear Suspensions are great for noise suppression and ride quality because they have multiple points of rubberized isolation between the tire and vehicle. The design allows for lower trunk floors for increased storage capacity, more room for spacious rear seating layouts and more room for crash crumple zones. Improved handling over traditional OEM suspension designs since an independent rear suspension set-up can handle high frequency bumps easily due to the suspensions low un-sprung mass and camber and toe curves allow for improved tire contact patch control under body roll and suspension articulation. The assembly process during vehicle production is drastically simplified because although the IRS unit itself is complex, when the car is moving down the assembly line the entire unit is prebuilt and can be installed in the car incredibly fast by tightening four subframe bolts, the driveshaft bolts and the brake caliper bolts so it’s minimal things to control which means more cars produced in less time.
Independent Rear Suspension (IRS) Downsides:
Now that we have covered why car manufacturers use independent rear suspension systems and the things, they are good for, let us talk about what they are not good for. Traction during straight line acceleration drastically suffers in any car that produces enough power where traction is an issue because rear wheel alignment angles like toe and camber make wheel control extremely poor because it allows almost no opportunity to convert the torque from the engine into suspension articulation to increase traction. Traction on hard acceleration coming out of corners is extremely poor and the rear end of the car is trying to push the back of the car sideways instead of forward for the same exact reasons stated above. Wheel camber and toe curves are designed for lateral loads, not longitudinal or rotational loads. Independent rear suspension are notoriously prone to wheel hop which is always a huge problem with any of today’s high powered sports cars and wheel hop not only negatively effects the vehicle’s performance, it is devastating on driveline components and the number one cause for broken axles, driveshafts, differentials, etc. Suspension tuning is not even an option on IRS equipped vehicles because of the non-adjustable hard points which make tuning camber and toe curves impossible.
Almost all of today’s independent rear suspensions are a very close copy of the E-series Mercedes of the mid 90’s, with much of the design structure and cradle mounts being such a close copy that many are interchangeable between the platforms. European and Asian roads along with their historic lack of high torque powerplants are the main reason why independent rear suspensions have been so widely adopted world-wide, along with ease of platform interchangeability. However, when it comes to nose-heavy, high torque, high horsepower American muscle cars, it just doesn’t deliver for what we need these cars to do which is effectively put the power to the ground because everybody knows that “spinning isn’t winning”. Tire companies have worked with auto manufacturers to create softer, stickier tire compounds to try and help these issues which has helped. Engineering teams have spent millions of dollars on traction and launch control systems, attempting to modulate power delivery in such a manner that helps to manage vector forces into appropriately loading the rear tires which has also helped. The truth is, although these things have helped, they are like putting a Band-Aid on a broken leg; better than nothing but you have not actually fixed the problem. All these advancements have only resulted in marginally better acceleration times, and extremely inconsistent acceleration rates. Aftermarket companies come out with things like better control arms to help eliminate wheel hop, differential braces to help support the differentials from the torsional loads applied during hard launches or the tremendous shock loads caused by wheel hop and these do help resolve problems associated with IRS set-ups but most of the products on the market today look shiny and fancy but end up creating poor ride quality and binding suspensions that still don’t allow for anti-squat or ideal camber and toe control. The tradeoff is better launch capability with super-sticky tires, but loss of handling, ride quality, vibration issues and excessive noise.
So why chose a 4-Link Suspension?
Looking at the vast majority of drag cars in the world, you will notice two distinct suspensions are used, 4-Link and Ladder Bar. Both accomplish similar tasks, but in different packages. Ladder bar suspensions are great for cars that have room to spare, but they can sometimes have excessive limitations on how tunable they are. 4-Link suspensions are easier to package and have excellent tunability, allowing the end user to change how hard the suspension hits, and ultimately the characteristics of the vehicle when it launches. When a Live-Axle 4-Link suspension has power applied to the pinion gear from the driveshaft, the pinion gear attempts is trying to climb the ring gear. As this happens the load is transferred into the snout of the differential housing, attempting to spin the differential housing and the entire axle in the car (basically trying to smash the driveshaft and pinion gear upwards into the transmission tunnel under the car). The 4-Link trailing arms can transfer this rotational force into the body of the car. The lower trailing arms are under compression (pushing) and upper trailing arms are under tension (pulling). Where these links are mounted on the axle and body 100% determine how the suspension handles the power applied to it. This geometry is easily plotted, and where the upper and lower links intersect in space, somewhere in front of the rear axle is called the Instant Center (IC). Depending on where the Instant Center (IC) is in space determines how much anti-squat the vehicle has, and how fast that anti-squat acts on the rear tires.
What is anti-squat?
Anti-squat is the action of the rear suspension pushing against the earth on acceleration. The rotational force applied to the differential physically pushes the axle into the ground. The force and rate of speed this happens is determined by the Instant Center (IC) location in space in relationship to the center of gravity. When the axle is forced to the ground, a measurable and momentary increase in tire loading occurs. This is extremely important because hundreds (sometimes thousands) of pounds of force are exerted during this action, and when properly timed, this creates the maximum amount of traction ever possible for a vehicle of a given weight. A perfect example of this is when a pickup truck with 70% nose weight can perform a bumper-scraping wheelie when combined with the right tire, shocks, power apply and a 4-Link suspension. You can also adjust the right 4-link geometry to force the nose of vehicle down so you can turn wasted energy from high flying wheelies into faster 60’ times and ET’s by directing that energy into pushing the car forward instead of towards the moon. This 4-Link suspension is completely tunable so that everyone at any power level can get the Instant Center where it needs to be for their specific application. The double adjustable shock valving allows the coil-overs to work for virtually every combination out there and since custom spring rates can be used the limitations of this system are virtually endless.
This system is not just made for street and drag racing, it is also easily tuned and ideal for road racing. Most drag cars shoot for 170-220% anti-squat, but road racing/autocross typically aim for 50-100% anti-squat. This suspension system is capable of anywhere from 0% to 500%+ anti-squat and it has also been designed to incorporate rear steering, essentially assisting turn-in and creating a vehicle that can navigate autocross much easier, as well as high-speed sweeping turns. The only situation where this suspension system will be slower than an Independent Rear Suspension is on extremely rough roads (washboard, or high amplitude low frequency imperfections) because the unsprung mass (the weight of the components that aren’t being held up by the springs and shocks) is relatively high on a 4-Link suspension when compared to an Independent Rear Suspension set-up, even though the overall weight of the unit is far less than that of the stock IRS. The 4-Link will be faster on most public roads and road courses, but if you live in an area with notoriously bad roads, or racing at LeMans, there may be surfaces that the car with an Independent Rear Suspension could be faster.
You can reuse your factory driveshaft, differential, half-shafts, wheel bearings, brakes, backing plates, emergency brake components, brake rotors and calipers. The power capacity of the differential and half-shafts is drastically increased due to girdling and elimination of wheel hop. You can also use any of our driveshaft upgrades, axle upgrades, differential upgrades including the Demon/RedEye stock 3.09 differentials, our full billet aluminum differentials and even the Ford 9” differentials. For anybody wanting to run 15” rear wheels our custom 15” wheel rear brake kits will bolt directly to this and no additional items are needed for a 15” rear wheel to fit perfectly.
This 4-Link suspension is the single most crucial component for maximum traction and the fastest acceleration that is pivotal to all street and drag racers. For the hard-core racer, they will also need to consider weight distribution/ballast, shock tuning, tire selection, power apply and more to create the world’s fastest 60’ times. There is no magic pill, but with a properly tuned 4-Link suspension you will be able to apply more force to the rear tires exactly when you need it over any Independent Rear Suspension system regardless of how many modifications or upgrades it has.
Since the best results will come from having both front and rear double adjustable coil-overs that will be the only way we offer this suspension system. Coil-overs will come with custom spring rates and the suspension will come fully tuned which will be adequate for 90% of the people out there. For the people who are hard core racers looking to shave every hundredth of a second off their track times we can assist with extremely fine tuning if you submit us quality video footage taken from beside the car as it leaves the line along with details such as launch rpm, etc.
Each unit will come standard with fixed camber and toe at 0.0-0.2 degrees negative camber and 1/16”-1/8” toe-out. Units can be special ordered with custom camber and toe specifications.
Upgrade Option: Live Axle 4-Link Rear Suspension System: +$12,500.00 (Includes Front & Rear Double Adjustable Coil-Overs with Custom Spring Rates & Suspension Tuning)
Upgrade: Forza 15” Rear Brake Kit: +$1650