MM News

Mustang Panhard Bar Tech

For 1979-2004 Mustangs equipped with a solid rear axle.

The Root of the Problem
1979-2004 Mustangs were not originally equipped with a Panhard Bar. They were manufactured with a four-link rear suspension design that has the rear upper control arms do two jobs. One job is to locate the axle laterally, which is done by the opposing angles of the two upper arms. Unfortunately, compromises in the design of the Mustang four-link prevent the chassis from being precisely located over the rear axle. The chassis will shift from side-to-side, relative to the axle, by up to 2 inches. The inconsistent movement of the rear axle causes a rear-steer effect.

"Rear-steer" means the rear of the car is steering itself, without any steering input from the driver. As the rear of the chassis moves sideways relative to the tire footprint, it causes the car to point in a different direction than where the driver is steering. To get the car pointed back in the direction the driver intends, he or she must correct course by steering the front tires. The rear steer effect makes the car unstable and unpredictable, requires continual steering corrections, and making the driver feel not completely in control of the car.

While the Mustang four-link design might be suitable for a commuter car, it cannot provide the handling prowess expected of a high performance vehicle. To make a Mustang handle well a much better method to laterally locate the chassis over the rear axle is required.

The Solution: The MM Panhard Bar
The MM Panhard Bar adds an aluminum rod as a lateral suspension link between the rear axle and the Mustang chassis. This simple design precisely controls the side-to-side location of the axle to eliminate rear steer. The unstable and unpredictable feeling typically associated with the stock four-link suspension is gone, making your Mustang easier and safer to drive!

Why choose an MM Panhard Bar, and not a Watts Link?
  • There are two good methods of controlling the side-to-side location of a rear axle, a Panhard Bar or a Watts Link. MM's Engineering Team chose the Panhard Bar because it provides a much lower roll center than a typical Watts Link design. More rear cornering grip is provided by a lower roll center than by a higher roll center.
  • The Tech page Busting the Myth of the Watts Link explains in detail why the MM Panhard Bar is the better choice for your Mustang.

Upper Control Arm Bushings
Whether or not your Mustang is equipped with an MM Panhard Bar, it is very important to have rubber upper control arm bushings. This is one application where the compliance of a rubber bushing is a benefit.

A four-link is over-constrained, a situation that requires the upper arms to physically change length as the suspension moves. Obviously, the metal control arm cannot change length. But its effective length, the distance between the control arm's two pivot points, can change because of the inherent compliance of a rubber bushing. If the ability of the upper control arms to change their effective length is hindered by a noncompliant bushing material, the suspension will bind up, and not move freely. The only way for the suspension to move is for the metal control arm mounting brackets to bend. The resulting restriction in the ability of the rear suspension to freely articulate will cause poor handling; the car will have a tendency to oversteer, and it may do so in a sudden and unpredictable manner.

Retaining the rubber upper control arm bushings is a necessary compromise for acceptable handling. MM has stock replacement upper control arms and axle-end rubber bushings.

See the Rear Lower Control Arm Tech page for more information about control arm bushings.

How it Works: The Complex Interactions of a Four-link rear suspension plus a Panhard Bar
As the suspension allows the chassis to move when bumps are encountered and as the body rolls during cornering, the rigid Panhard Bar keeps the chassis centered over the rear axle, something the stock four-link design fails to do. The opposing angle of the Mustang upper control arms causes the chassis to move in an odd path when the body rolls, which tries to make the chassis shift sideways relative to the axle. Rubber upper control arm bushings deflect enough to allow the chassis to follow the path determined by the Panhard Bar, and do so without significant suspension binding.

The stock 2005-2014 Mustang rear suspension has a three-link plus a Panhard Bar. Having only one upper control arm eliminates any binding related to the requirement of two upper arms to change their effective lengths.

The MM Torque-arm suspension for Fox/SN95 Mustangs turns the stock four-link into a variation of a three-link, eliminating bind from the suspension. The result is more rear grip, both when cornering and when launching from a standing start.

Unique Features of the Maximum Motorsports Panhard Bar for the Fox/SN95 Mustang
  • MM's Panhard rod is the longest possible at 38" between pivot points. The longer the rod is, the less the amount of the rear axle's lateral movement due to the arc of the rod's travel. The longer the rod, the larger the radius of the arc. The larger the radius, the smaller the sideways movement during bump and droop travel.
  • How much lateral movement? Very little. The arc of the MM Panhard Bar causes a maximum lateral movement of 0.17". This maximum occurs only when the body rolls all the way to full bump or full droop. This much suspension travel very rarely occurs during hard cornering. More typically, suspension travel is less than 2". The arc of the MM Panhard Bar at 2" of travel causes only 0.050" of lateral movement of the chassis relative to the axle. Even when more extreme cornering loads cause 2.5" of travel, there is still just 0.079" of lateral movement. During normal street driving, when it's more typical for suspension travel to be 1", the resulting lateral movement is a minuscule 0.010". These dimensions are small enough to be irrelevant.
  • A slot on the MM chassis mount allows for vertical height adjustment to allow leveling the Panhard rod during installation, to accommodate different vehicle ride heights. A level bar minimizes lateral motion over the range of suspension travel.
  • Custom spherical rod-ends have a large 3/4" shank and a 5/8" bore.
  • The rod ends are mounted in double shear in the mounting brackets at both ends.
  • The unique design and quality materials of the MM axle and chassis mounts ensure they are strong enough to not break, and stiff enough to not flex, even when cornering loads exceed well over 1 G.
  • Maximum Motorsports' boxed Panhard Bar axle mount bracket encloses the rod-end for a rigid, non-flexing mount.
  • The MM chassis bracket mounts to the rear frame rails of the car, not the flimsy trunk floor or spare tire well.
  • MM's exclusive Panhard Bar frame inserts fit inside the rear frame rails. These provide a structurally sound attachment point for the MM Panhard Bar chassis mount.
  • The MM Panhard Bar is designed to clear the factory tailpipe routing. Aftermarket 2.5" tailpipes that follow the factory routing will usually clear the MM Panhard Bar without modifications to the tailpipes. These brands usually fit well: Dynomax, Flowmaster made after 2000, Late Model Restoration. These brands require significant modifications to fit: Flowmaster made before 2000, Bassani, Borla, Magnaflow. Due to the wide tolerances of exhaust systems, your experience may vary.
  • With a Panhard Bar the roll center is essentially located at the height of the rod. The MM Panhard Bar for Fox/SN95 Mustangs lowers the rear roll center about 9" from the stock height, to just below the differential cover.
  • Mustangs handle better when the rear roll center is lowered from the stock location because a lower roll center increases rear grip by reducing the tendency of the inside rear tire to unload during cornering. Here's the really short explanation: compared to a lower roll center, a higher roll center causes more jacking forces, which raises the center of gravity height, which increases lateral weight transfer, which transfers weight from the inside tire to the outside tire, which reduces overall cornering grip.
  • The MM Panhard rod itself is a lightweight aluminum tube. It is available in either natural finish or polished. The MM Engineering Team designed an exclusive custom-extruded aluminum tube sized to precisely fit 3/4" rod ends, and with a very thick wall to provide adequate stiffness to prevent deflection during hard cornering.
  • While a properly installed MM Panhard Bar is compatible with most aftermarket aluminum differential covers, we do recommend the low-profile covers listed for the S197 model to ensure there is no interference.

The next logical step after the installation of the MM Panhard Bar is the installation of an MM Torque-arm. Upon installation of the MM Torque-arm the rear upper control arms are removed. This eliminates the bushing deflection problem, and finally removes the last source of binding in the rear suspension. Maximum Motorsports also has complete MM Torque-arm Suspension System packages.

Baer Brakes
Baer brake systems using Camaro-sourced PBR calipers relocate the calipers, which causes the parking brake cables to interfere with the MM Panhard Bar Axle Mount. MM has relocation brackets for one of the Baer kits: 12" rotors for the 1994-04 Mustang GT.