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Mustang Rear Lower Control Arm Tech

Improve your Mustangs traction and handling with Maximum Motorsports Rear Lower Control Arms. Taming the antics of the rear axle is critical to raising the Mustang's performance level. The rear axle motion allowed by the stock 4-link causes poor traction and poor handling characteristics. Whether your goal is to improve your Mustang's launch or its cornering ability, we have the control arms you need. The superior design of MM Rear Lower Control Arms increases traction and performance, without the torque box damage and poor handling characteristics commonly associated with other aftermarket control arm brands!

Scroll down for an overview of MM rear lower control arms.

For Tech specific to each series of MM control arm:

Specific tech about the MM Heavy Duty control arms

Specific tech about the MM Extreme Duty control arms

Specific tech about the MM Road Race control arms

Mustang Rear Lower Control Arm FAQs

Drag Racing-It's the Launch
Lowering your 60-foot times will lead to a lower ET. Improving the launch by a tenth of a second usually results in a 2/10 lower ET. In the search for a better launch, racers often attempt to improve bite off the line by installing better rear lower control arms. Just what constitutes a "better" rear lower control arm? While replacing the stamped-steel OEM units with stiffer tubular arms is an improvement, the real key to a better rear lower control arm is in the bushings.

Street Performance and Road Racing-It's the Control
All of the forces that accelerate the car, as well as much of the braking loads, pass through the rear lower control arms. In stock form, the excessive deflection allowed by the original rubber bushings prevents the rear axle from maintaining its correct position under the chassis. The axle is allowed to shift forwards, backwards, and sideways under the car, leading to poor traction and poor handling.

To improve handling and traction it is vital to control the motion of the rear axle. The key to better axle control is in the bushing design. A proper bushing design will provide precise location of the axle while also allowing the motion required for the suspension to function. MM has achieved the twin goals of great handling and great traction with each of our different series of rear lower control arms.

To adjust, or not to adjust...
Both our Heavy-Duty control arms and our Extreme-Duty arms are available in two basic styles: Ride height adjustable or non-adjustable. Both styles are available with mounts for a factory-style rear swaybar, or without swaybar mounts, for use with the MM Adjustable Rear Swaybar.

Non-adjustable Control Arms
Non-adjustable control arms are available with a fixed-position spring perch that maintains the same ride height as a stock control arm, or without any spring perch at all, for coil-over applications.

Adjustable Control Arms
Adjustable Control Arms allow you to raise the rear ride height by up to 2 inches, or lower it as much as 1 inch. The spring perch design allows easy ride height changes, with the car still on the ground. Drag racers can use these arms to easily fit larger tires, and improve traction by fine-tuning the instant center location and anti-squat geometry by changing the ride height. Road racers and autocrossers can set not only the ride height, but also corner weights, for optimum handling. A Mustang with 200 pounds of stereo gear in the trunk can have the rear ride height adjusted back up to normal.

The "Heavy-Duty" control arms are for street performance. The "Extreme-Duty" control arms are for Mustangs with high horsepower, Mustangs that are raced, and even street-driven Mustangs that are launched hard from a standing start.

Standing Starts and RLCA Bushings
Urethane rear lower control arm bushings should not be used for any type of drag racing. The statement "any type of drag racing" includes any hard standing start launch, whether it is at the drag strip or a stoplight on the street. Hard launches, when the engine RPMs are increased significantly and the clutch is released abruptly, put an enormous sudden shock load on the control arm bushings. Urethane bushings will suffer a shortened lifespan from this type of use. The higher the power level, the stickier the tires, and the better everything else that helps a car launch more quickly is, the greater the stress on urethane bushings, and the shorter their lifespan. If hard launches are part of your lifestyle, then you want the MM Extreme-Duty Rear Lower Control Arms.

Specific tech about the MM Extreme Duty control arms

Good Research is the Basis of Good Engineering
Instead of simply making control arms the same way as everyone else, MM's designs are the result of extensive motion analysis of what actually occurs when the rear suspension moves over bumps, and during body roll. We then designed control arm bushings that provide what is needed to improve traction and handling.

We tested other aftermarket control arms, and found that most use bushing designs that actually cause an increase in suspension bind, when compared to stock! Control arms that use hard urethane bushings at each end increased the wheel rate by almost 400%! For comparison, as little as a 10% increase in rear wheel rate will have a noticeable effect on the handling balance of a car.

The concept of wheel rate is similar to that of spring rate. To put it into simple terms, the wheel rate is measured at the wheel, not at the spring. Poorly designed suspension components can prevent the control arms from articulating properly during bump and body roll, and therefore cause suspension bind. This suspension bind will cause the wheel rate to increase unpredictably, adversely affecting handling.

So, why does the wheel rate increase? In the Mustang's rear suspension design, whether it is still the stock 4-link suspension design, or has been modified to a Torque-arm or three-link design, the control arms do not simply pivot around the mounting bolts. The arms also move sideways, with an angular motion (relative to the pivot axis). If that angular motion is restricted because of a poor bushing design, the suspension will bind. All Maximum Motorsports rear lower control arms allow the necessary freedom of movement, while continuing to positively locate the axle in the fore-and-aft direction. The engineering expertise we put into our unique bushing designs puts the MM control arms in a class above the rest!

Most aftermarket rear control arms use either hard 2-piece urethane bushings or some form of solid bushing. These types of bushings do not allow the angularity needed for the Mustang rear suspension to move freely. The resulting suspension bind causes the rear tires to break loose very easily. Suspension bind not only causes poor handling and poor traction, but it also causes damage to the torque-boxes. Torque box re-enforcement is rarely necessary with a properly designed set of rear lower control arms, such as MM's.

Stop wheel hop
Ford's solution for reducing wheel hop was to add the quad shocks (the two horizontal shocks mounted behind the rear axle). They reduce wheel hop by damping axle wind-up. Axle windup is caused by two independent deflections: the control arms, and the rubber bushings.

MM's rear lower control arms eliminate the primary causes of axle wind-up. Our tubular steel arms are over three times stiffer than the stock control arm, and our unique bushing designs eliminate the deflection of the soft stock rubber bushings.

Stop Torque-box Damage
Torque-box damage is often blamed on "too much power". Wrong! It is usually the result of metal fatigue caused by a poor rear lower control arm bushing design.

It is commonly believed that as long as the rear lower control arm bushings do not deflect, they must be okay. Not true. Any up and down suspension movement causes the rear lower control arms to not only rotate on their pivots, but also to change their angularity, relative to their chassis-end and axle-end mounts. If the rear lower control arm bushings are not designed to accommodate this change in angularity, the suspension will tend to bind up and not move freely. That hurts traction, and can damage the chassis-side mounts (the lower torque-boxes) for the rear lower control arms. While the repeated binding of suspension movement may not harm the steel of the axle-housing bracket because it is quite thick, the thin sheet metal of the chassis mounts will fatigue and eventually fail.

Installing rear lower control arms that allow proper articulation of the suspension will prevent torque box damage. The only proper rear lower control arm bushing for a drag race car is a spherical bearing, not a solid (pivot-only) style of bushing. Surprisingly to many, this is also the best design for a road-race car.

Specific tech about the MM Heavy Duty control arms

Specific tech about the MM Extreme Duty control arms

Specific tech about the MM Road Race control arms

Mustang Rear Lower Control Arm FAQs

2-1/2" springs with MM RLCAs
Using the MM Adjustable Rear Lower Control Arms along with our weld-in upper spring adapter allows the use of standard 2.5" (inside diameter) coil-over springs. Why use coil-over springs in the stock location, on the control arm? Because the coil-over springs have a linear rate, and are available in a much wider range of spring rates. This can help when fine-tuning a car's handling to suit the driver's preferences. This is particularly useful when coil-overs have been installed on the front, but not in the rear of the car. We recommend this setup for track use only; for street use a traditional rear spring is much more suitable.