The lights on the tree glow. The engine revs higher. The driver drops the hammer. The engine’s snarling output hurtles through the powertrain to the rearend, where it spins the wheels shod with sticky racing rubber. The car lurches forward, but the passenger-side rear suspension compresses and unloads the driver-side rear wheel.

Evenly loading both rear tires will allow you to put down more power… — Greg Ionadi, BMR Suspension

It’s a familiar scenario for those drag racing a Fox, SN-95, or New Edge Mustang. These cars are long proven as potent straight-line performers, but the factory four-link rear suspension has its limitations. If there is enough power and traction onboard, physics overwhelms the design, power is wasted in the excessive movement, and traction is lessened by the uneven application of rubber to the racetrack.

Ford’s 1979-2004 Mustangs are amazingly adaptable machines. In their factory form they aren’t optimized for performance, but the design of the Fox and Fox-4 platforms makes them easily upgradable to perform at a high level. On the drag strip the factory four-link rear suspension allows the body to twist, which applies engine output unevenly to the rear tires. An anti-roll bar will cure that, and BMR Suspension has two new options. (Photo Credit: Courtesy of NMCA)

“The deflection of stock style rubber bushings and control arms in conjunction with a poorly mounted stock sway bar do very little to alleviate wheel hop and body twist,” Greg Ionadi, Product Design Engineer at BMR Suspension, explained. “Any live axle vehicle is going to have some body twist associated with hard launches. An anti-roll bar uses a large diameter tube that links the axle to the frame. It allows the suspension to travel up and down without one side of the suspension compressing more than the other.”

Tame The Twist

BMR recently released two anti-roll bar options for Fox- and Fox-4-platform Mustangs, allowing owners of 1979-2004 Mustangs with solid rear axles to eliminate the body twist and optimize traction for improved straight-line performance at the racetrack. These two bars use unique designs to address the needs of single- and dual-purpose machines.

“We wanted to give customers an option for both street/strip cars as well as all-out race cars. The ARB730 is a great option for someone who wants to have all of the benefits of a drag racing anti-roll bar while still maintaining clearance for over-axle tailpipes and mufflers, as well as being easy to install,” Ionadi said. “The ARB732 is designed to accommodate all-out drag cars with modified rearend setups that are OK with sacrificing tailpipes and increasing installation difficulty in order to achieve maximum performance.”

The street/strip kit (PN: ARB730) features a bar built from 1.25-inch heavy-duty drawn-over-mandrel tubing, 0.179-inch laser-cut steel mounting plates, Teflon-lined rod ends, 88-durometer greaseable polyurethane bushings, and Grade-8 fasteners. By using its three adjustable positions, the sway bar rate can be adjusted between 1,593 to 2,724 pounds per inch. Meanwhile, the racing bar (PN: ARB732) is based on 1.375-inch-thick tubing, and can be adjusted to deliver a rate of 2,922 to 4,734 pounds per inch based on its mounting position.

“They both are similarly constructed using 3/16-inch steel plate that is TIG welded to seamless, drawn-over-mandrel, thick-wall steel tubing. Both kits contain high-strength, Grade-8 hardware. All components are manufactured in Florida and are powder-coated or zinc-plated to provide long-lasting corrosion resistance,” Ionadi said. “The ARB730 is mounted using polyurethane bushings to reduce road noise going into the chassis during street use, whereas the ARB732 is mounted by captured with spherical bearings and road noise is more pronounced. The ARB732 has a stiffer sway bar rate due to its larger tube diameter. This makes the ARB730 easier to drive on the street, but we do recommend disconnecting one of the end links when doing so.”

To install the system, you must raise the car and support it with jackstands or use a lift. Then you can remove the rear wheels. Disconnecting the tailpipes and mufflers will give you more room to work. Start by bolting on the sawtoothed axle mount loosely, then place the saddles on the sway bar mounts and bolt them to the axle mounts. The mounts should be installed as wide as possible, but be sure they are equidistant from the lower control arm brackets. The anti-roll bar should be centered and level, so measure the distance from those brackets and use an angle finder to ensure it is level. If everything looks good, torque the U-bolts and sway bar saddles to 45 lb-ft.

Purpose Built

Designed with a deference to vehicles that will see significant street duty, the street/strip bar is built to balance performance with the introduction of noise into the passenger compartment.

“While the ARB730 will not have any major increase in NVH due to its use of polyurethane bushings, you will experience some with the ARB732. Ford designed these vehicles to perform well, while also allowing your grandmother to comfortably put down 300 wheel horsepower,” Ionadi said. “When modifying your vehicle, there will always be a tradeoff between comfort and performance, especially when you reach the limits of your stock suspension.”

For those more concerned with all-out performance than hearing driveline vibrations and suspension noises, the racing bar stops being polite and starts being real courtesy of its rugged bearings.

“One main difference the ARB732 has is the fact that the sway bar pivots use 1-inch, Teflon-lined spherical bearings. These bearings are replaceable and serviceable, unlike other bars that use sintered-bronze bushings and are captured and welded in place,” he added. “The entire sway bar can be unbolted from between the frame rail and removed if required. In addition, just like all BMR Suspension products, the ARB730 and ARB732 are designed and manufactured right here in the USA.”

While you can leave the bars installed and run them on the street, it would be unwise to leave them in the same configuration used on the racetrack. The racing configuration is too restrictive for a car that needs to traverse a variety of road surfaces and make frequent turns.

Bigger Bar

While the BMR’s street/strip anti-roll bar will deliver a significant improvement in traction, it does make some performance compromises in the name of noise, vibration, and harshness, so as not to make your Fox’s streetability suffer. For those who have dedicated race cars or simply don’t care about the increased noise and harshness, BMR also offers a race anti-roll bar for these cars.

“It really depends on how hard the car can launch and what goals you set for your car. The ARB730 will be a better option for street cars wanting to correct a body-twist issue, that are also retaining a stock axle,” Greg Ionadi, Product Design Engineer at BMR Suspension, suggested. “The ARB732 will be a better option for cars making a lot more power that have an aftermarket axle or axle tube braces which limit where the anti-roll bar can be placed.”

More than just the level of performance, choosing the right anti-roll bar for your application may come down to what other upgrades and hardware you have installed on your Mustang.

“The limitations of the ARB730 aren’t necessarily a performance threshold, but rather limitations from how you have the car set up,” he added. “For example, if you have bracing on the rearend for a pro-jack, or modified frame rails in a mini-tub kit, you will need the ARB732 to accommodate those other modifications.”

Rather than mounting the bar to the axle and connecting it to the frame with end links, the race version mounts the bar directly to the frame with welded mounts and attaches the end links to the axle tubes via weld-on tabs. This makes the installation more compact, and the connection more direct. The bar is also larger at 1.375 inches in diameter and fortified via the aforementioned spherical bearings. In all, this bar is better equipped to plant big power at the track.

Street or Strip

“While using these bars on the street, it is recommended to keep them in the softest setting,” Ionadi said. “Additionally, you can completely disconnect one end link if you drive in an area with rough roads, hard pavement transitions, or tight turns. The purpose of these bars is to keep the chassis parallel with the axle in order to accelerate in a straight line as fast as possible. Cornering characteristics will be dramatically altered, and the possibility of damaging the chassis becomes a possibility with sub-optimal road conditions.”

With the system fully installed and adjusted, racers can dial in the traction to optimize the on-track performance. By how much depends on the combination, but with the body twist gone and the tires planted evenly on the track, your Fox is sure to outrun its best times with the stock four-link setup.

“That is based on how your car is currently performing. The more power you are trying to put down, the more you will benefit,” Ionadi explained. “Evenly loading both rear tires will allow you to put down more power, especially when you are dealing with limited traction like small-tire, no-prep racing.”

Of course, either BMR anti-roll bar is only part of a complete suspension. If you are bolstering your Fox for straight-line performance, BMR offers a host of other suspension and chassis upgrades to round out your combination.

With everything buttoned up, you are ready to put the car on the ground and head to the drag strip to run a new personal best courtesy of that BMR Suspension anti-roll bar.

“The most critical components that you need on a Fox/SN-95 Mustang are control arm-relocation brackets to set your bar angle to help plant the tire. You will also need stronger upper and lower control arms to eliminate the deflection from the rubber bushings and stamped steel design of the stock arms,” Ionadi added. “As you are trying to put down more power, subframe connectors and torque-box reinforcements will help keep from damaging the chassis. We have many options for each of these components on our website. Our team of sales assistants is also more than happy to help select which parts are right for your setup.”

To learn more about the BMR anti-roll bars and other upgrades, visit the company’s website here.