Suspension Modification Upgrades - Getting A Grip

It goes without saying that the Chrysler Corporation designed some pretty solid engineering into the OE suspension of our beloved Mopar vehicles. The front torsion bar/rear leaf spring suspension earned the '57 Plymouth Motor Trend Car of the Year honors in the year of its debut. As the musclecar era developed, this combination proved more than capable of dominating on both circle track and straight-line competition circuits, and it is not surprising that today's popular V8 SUVs continue using a torsion bar/rear leaf combination in many cases.

With more and more of us driving our cars these days, we thought it would be a good idea to give some basic information on some changes that can be made to your suspension for either track time or handling chores. Of course, there is always a fine line as to what type of end result you are trying to achieve. For example, removing front-end weight is important in drag cars, but making sure the vehicle can still go around corners, especially in dual-purpose machinery, is an even more critical aspect. Here are a few things you might want to consider as you put together your own dream machine.

Sway Sense
Front and rear sway bars were not part of Chrysler musclecars until the debut of the T/A/AAR Trans-Am E-Bodies in 1970, the first vehicles to employ both. Front sway bars were part of many musclecars starting in the mid-'60s, although garden-variety machines didn't utilize them. In 1971, the factory began adding a rear sway bar as part of the differential package on many E- and B-Body cars. As for A-Bodies, rear sway bars were rare; the only one I remember seeing was under a '76 police car.

Today, there are aftermarket sway bars available for most of the muscle-era cars; check out Mopar Muscle suspension advertisers for your application. These are normally 1/8-inch to 1/4-inch larger than the OEM versions. Simply going from the rubber to polyurethane bushings will show an increase in handling ability as well, something that is very important in any big-block car. Renewing the bushings in shocks, control arms, leaf springs, and strut bars will also aid you here. Just remember to disconnect the stabilizer bar links when hitting the drag strip so the front suspension can transfer weight properly.

Torsion Trials
For many people who drag race, one easy switch is to change from V8 to six-cylinder torsion bars under the frontend. Removing the torsion bars is a fairly simple mod, but be sure to consider what you plan to do with the car. If it's more street than strip, the V8 bars were designed to help the frontend take road abuse.

The A-Body line from 1963-1976 used a 35.8-inch bar, while '62-'72 B-Bodies and all E-Bodies used a 41-inch bar. In bone stock form, the bars' thicknesses ranged from 0.83-inch to 0.96-inch; circle track machines requiring stock-style suspensions had bars as thick as 1.25. The aftermarket offers many varieties, and you might even get a set from the boneyard. Replacing torsion bars is not a matter to take lightly; consult with suspension aftermarket people and other knowledgeable sources of information. The ones who know what they are doing will talk to you. The facts that you should have ready are rear spring stiffness, engine and vehicle weight, tire and wheel sizes (front and rear), and other specifics.

While we are on the subject of front suspension and weight, lightening the weight ahead of the cowl is an easy way to get better launch and handling characteristics. Power steering pumps and related equipment can add as much as 50 pounds to the car (though, again, since both my Challenger and my R/T are street driven, I have left them in place). Adding aluminum heads and intake, an aluminum water pump, moving the battery to the trunk, and other tricks can bring the car into a much better front-to-rear weight ratio. For serious street/strip cars, manual steering is the way to go. For those who want to go around corners, there is also the optional 16.1 fast ratio steering box; the standard version is 24.1.

Leafing Through
While there remains some debate as to how much good bolt-on traction bars do, the truth is that Chrysler factory engineers were experts at rear leaf design. The rear axle sat approximately 1/3 of the total distance from the front mount, which drastically limited axle wind-up; a pinion snubber that would cause the differential to brace down on the floor pan was the recommended course of action. Brand X machines with leaf springs normally had the rear centered on the leaf package, meaning that the front of the spring had much more wind-up room. The 426 Hemi and 440 cars benefited from a massive pack of five springs on each side, with an extra half-leaf added to the left and two extra half-leaves on the right (this was due to the direction of engine torque, and the reason why rear-mounted batteries should be on the right, or passenger, side of the car). Depending on your needs, there are a wide variety of spring packages available for A-, E-, and B-Body cars, and many people select the Super Stock springs that MP offers. Of course, full-out cars often go to a four-link/coil-over shock layout for increased adjustability.

One final possibility is using the newly-released mono-leaf style springs as covered in Mopar Muscle last month ("All for One and One for All," p. 71).

Shocking Discoveries
Since shocks are often the simplest things to change and come in many variations, we saved those for last. Coupled with all of the possibilities mentioned above, selecting the right shocks is critical to making it all work properly. Shocks serve two main purposes: They control and dampen spring and suspension movement, and, in that capacity, they allow that suspension to travel at a given rate of speed and distance. This is critical to keeping all four wheels on the ground, regardless of application.

Shocks "bounce" (referring to the up-and-down movement of the suspension), "jounce" (upward suspension travel that compresses the shock), and "rebound" (downward travel that extends that shock). If a shock is worn, that chuckhole you hit by accident might cause the suspension to bounce more than once, and the wheel affected can leave the surface of the road entirely-not a good situation when you are moving two tons of B-Body around!

While this is the primary role of any shock absorber, there are special kinds of shocks that control suspension movement differently. Hydraulic shocks, which are oil-filled, non-gas-charged varieties, were OEM in the musclecar era; today you select that type or gas-charged shocks, air-filled shocks, and "load levelers" (which are used in conjuction with a coil-over spring). Gas-charged versions are oil-filled, then filled with nitrogen and sealed; the pressurized nitrogen keeps the shock cooler and prevents aeration of the oil during shock movement, ensuring solid hydraulic flow. Any car will see an improvement in handling with the installation of gas shocks over standard hydraulics.

The trick at the track has always been a 90:10-ratio travel front shock, but these are not recommended for use on the street; they will not control the car in handling situations and could result in an accident. Dual-purpose cars can use a 70:30 ratio or even a 50:50 ratio (for mostly street-driven machines) with good results. Many companies now offer three-way adjustable front shocks that you can dial-in to the dampening, or travel, ratio you desire. To have your cake and eat it, too, there are now some 12-way adjustable shocks available. At $150 per side, they are pricy, but will let you have the best of both worlds. If you are changing from heavy stock wheels to narrow, lightweight front wheels and tires (also a no-no on the street) once you get to the track, you can always simply swap in a set of 90:10s while the car is jacked up.

Load-levelers do what the name implies: coupled with a coil-over outer spring, they greatly increase the carrying capacity. Today, they can even be had in gas-charged versions. I used these on a '68 Chrysler 300 parts-chaser I owned, and had a set on a '67 GTX in which I carried a lot of tools, and they made a real difference. They will not make any major difference one way or another on the dragstrip.

Air shocks are a combination of air spring and shock absorber, and this is what is on the R/T right now (they have been under the car since the '80s when raised back ends and white air shocks were the "deal"). Air shocks allow you to adjust the shock's performance based on the load; when I am driving to the track with slicks and test parts in the trunk, I can pump them up to 50 pounds (they'll take 150 psi) to maintain ride height and keep the pinion snubber an inch off the floorpan. At the track, I run 20 psi in the passenger side (right rear) and 10 psi in the driver's side (left rear), which, when coupled with the Super Stock springs, keeps the snubber 1/4 inch off the floor pan. Route the air lines away from exhaust components for obvious reasons, and use two separate inlets (one for each side) so you can accurately judge and adjust pressure levels.

Conclusion
Suspension science is not difficult; the factory did a lot to make getting a grip with your Mopar an easy task. Decide what you will do with the car and buy parts according to the overall need of your package. Street/strip cars will indeed benefit from upgrades and doing it right will keep you from having any "shocking" experiences later!