J&M Rear Lower Control Arms w/ Polyurethane Bushings (1999-2004 Ford Mustang)

1999-2004 Ford Mustang Street Performance Rear Lower Control Arms

The control arm bushings found in the Mustang automobiles can have a significant impact on the vehicle's ride, comfort, handling, acceleration, noise and vibration. When the car leans (i.e., rolls) in a turn, one side of the chassis moves upward relative to the rear axle, the other side moves downward, and the control arms must twist to allow for the axle to articulate. This causes the control arm bushings to bind. If this bind becomes excessive, it will raise the rear wheel rate and produce sudden, uncontrolled, undesirable changes in handling (e.g., snap oversteer).

Ford minimizes this suspension bind by using compliant rubber bushings in both lower control arms. These relatively "soft" bushings help accommodate the necessary motion of the control arms during body roll. However, the rubber bushings do not provide much in the way of forward and aft support, which can cause wheel hop during hard acceleration and braking.

It has become common practice to replace the stock rubber control arm bushings with solid or two piece polyurethane bushings to resolve the shortcomings of the soft rubber bushings. Hard polyurethane bushings eliminate wheel hop, reduce axle deflection, and improve rear straight line grip. However, the downside of common aftermarket bushings such as delrin, steel, stiffer rubber, solid or two piece polyurethane bushings is they prevent the necessary movement of the control arms during body roll, which in turn produces significant binding in the suspension when the vehicle is cornering. The polyurethane bushings also place unnecessary high stresses on the torque boxes, which are the attachment points for the control arms to the chassis. Standard aftermarket control arms do not allow for rotation of the control arm during cornering because of the stiffness of the bushings.

The Solution:
We at J&M Products designed and built a tubular lower control arm which eliminates the unwanted uncontrolled control arm flex. Our tubular control arms CNC laser cut from high strength 2.00" round tubing to guarantee a perfect fit every time. Unlike most other companies who use the basic mig weld process, we use a pulse weld process which is stronger than even tig welding.

We then solved the shortcomings of the factory rubber and other aftermarket polyurethane and stiffer rubber bushings. This was accomplished with our 3 piece Poly-Ball bushing combination. By spending countless hours looking and dissecting the geometry and the need of the rear suspension we come out with bind-free bushings set up. Our Poly-Ball bushing combination incorporates a very hard inner synthetic elastomer ball which is surrounded by soft socket outer cups. This combination allows the bushing to articulate like a spherical bearing during cornering but the hard inner ball does not allow the bushing to deflect during acceleration giving you great traction during acceleration like solid bushings but remains completely bind free like a spherical bearing during cornering for great predictable traction in the corners. Available in Black and Red Powdercoated finish.

The Testing:
We built a fixture which simulated a factory control arm mounting and tested how much force was needed to make the control arm articulate (twist) in those mounts and the results where astounding.

Poly-Ball Bushings:

• 5 degrees of total rotation = 26.1 foot/pounds of torque
• 7.5 degrees of total rotation = 35.8 foot/pounds of torque
• 10 degrees of total rotation = 41.7 foot/pounds of torque

Standard 2 piece setup using only 85 durometer bushings:

• 5 degrees of total rotation = 124.7 foot/pounds of torque
• 7.5 degrees of total rotation = 156.4 foot/pounds of torque
• 10 degrees of total rotation = not measurable with fixture.
• The 1/2" grade 8 bolt twisted in half at 9.2 degrees which was 210 foot/pounds of torque.