This is copied from MM's website: They can say it better than I can.--
Rear
Lower Control Arms
Improve traction and handling with Maximum Motorsports Rear
Lower Control Arms. Replacing the stock rear
lower control arms, and their soft rubber bushings, with MM Rear
Lower Control Arms will keep your tires firmly planted on the road.
What sets MM Rear
Lower Control Arms apart from all the rest?
It’s the engineering expertise we put into our unique bushing designs. Instead of simply making
control arms the same way as everyone else, we first analyzed the Mustang’s rear
suspension geometry, and then designed control arm bushings to provide what is needed to improve traction and handling. The superior design of MM rear
lower control arms increases traction, without the poor handling characteristics commonly caused by most other aftermarket
control arms.
The rear
control arms connect the rear axle housing to the chassis. All of the forces that accelerate the car, as well as the braking loads, pass through the rear
control arms. In stock form, the deflection of the rubber bushings prevents the rear axle from maintaining its correct position under the chassis, leading to instability from rear steer. During acceleration, the rear tires push the axle forward, which in turn moves the car forward by pushing on the rear
lower control arms. Replacing the rear
lower control arms with MM
control arms will improve traction and handling primarily because of the elimination of the overly compliant stock rubber bushings. With MM rear
lower control arms, the properly designed bushing mounted in a stout tubular arm keeps the axle correctly positioned under the chassis. Traction and handling are both improved because the axle does not move around in an unpredictable manner.
Most aftermarket rear
control arms use hard 2-piece urethane bushings, Delrin bushings, or steel bushings. Those types of bushings do not allow the angularity needed for the Mustang’s
suspension to articulate 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. As the attachment points on the chassis for the rear
control arms, the torque-boxes can suffer greatly from the abuse of poorly designed control arm bushings. After all, the torque boxes are only made of folded sheet metal.
Stop wheel hop
Ford’s solution for reducing wheel hop was the addition of the quad shocks (the two horizontal shocks mounted behind the rear axle). They reduce wheel hop by dampening axle wind-up. Axle windup is caused by two independent deflections: the
control arms, and the rubber bushings. Deflection of the
control arms is eliminated because the MM arms are over three times stiffer than the stock control arm. Deflection of the soft stock rubber bushings is eliminated by our unique bushing designs. These designs are the result of extensive motion analysis of what actually occurs when the rear
suspension moves over bumps, and during body roll. Installing MM’s rear
lower control arms eliminates the primary cause of wheel hop, which is the deflection of the stock
lower control arms and their bushings. While there are other factors besides the compliance of the control arm bushings that cause wheel hop, the MM arms usually reduce axle wind-up enough to allow removal of the factory quad shocks.
Good Research is the Basis of Good Engineering
The concept of wheel rate is similar to that of spring rate. But, 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.
To analyze the geometry involved, Maximum Motorsports used a full-scale mock up of the rear
suspension. When we tested other aftermarket
control arms, we found that most use bushing designs that actually cause an increase in
suspension bind, compared to a stock control arm!
Control arms that had hard urethane bushings at each end increased the wheel rate by 400%! For example, as little as a 10% increase in rear wheel rate will have a noticeable effect on the handling balance of a car, because the rear cornering grip will be noticeably reduced.
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. 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. While some aftermarket
control arms may seem to improve performance because of reduced bushing compliance, it is only improved to a level slightly higher than the stock
control arms. Once the car is pushed past that level, the increased wheel rate from the
suspension bind will cause unpredictable handling– not to mention damage to the torque boxes.
To avoid that nasty situation, the two different bushing configurations of both the MM Heavy-Duty and Extreme-Duty Rear
Lower Control Arms allow the necessary freedom of
suspension articulation, while continuing to positively locate the axle in the fore-and-aft direction.
MM offers two different types of rear
lower control arms: Heavy-Duty and Extreme-Duty. The difference between the two is the bushing configuration. The Heavy-Duty arms are suitable for cars with moderate horsepower levels that are not drag raced. We recommend the Extreme-Duty
control arms for any car that is drag raced, and any car with the higher horsepower levels that come with superchargers, larger displacement engines, etc.
To adjust, or not to adjust...
Both our Heavy-Duty
control arms and our Extreme-Duty arms are available in two basic styles: Non-adjustable, or adjustable for ride height. These two styles are available with several different options for spring perches and swaybar mounts. This ensures that we have exactly what you need for your car.
Non-adjustable
Control Arms
Non-adjustable 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. These
control arms are available with mounts for a factory-style rear swaybar, or without any swaybar mounts, for use with MM's Adjustable Rear Swaybar.
Adjustable
Control Arms
The easy adjustment of MM's Adjustable
Control Arms allows raising the rear ride height by up to 2 inches, or lowering it as much as 1 inch. A heavy-duty weight-jack bolt, similar to those used in NASCAR, makes this possible. The spring perch design allows easy ride height changes, with the car still on the ground. Road racers and autocrossers can set not only the ride height, but also corner weights, for optimum handling. A car can be fully loaded up with gear for a road trip, and then have the rear ride height adjusted back up to normal, to avoid bottoming out. These
control arms are available with mounts for a factory-style rear swaybar, or without any swaybar mounts, for use with MM's Adjustable Rear Swaybar.
UPR i love my upr controll arms they work great for me, i know a few others that run them to and like them just as much as the mac and bbks.
