Having been straight-line guys for most of our car lives, building an open-road racer is a foray into the unknown. The front suspension on our '89 Diplomat cop car was shot and in need of a freshening up. A clean bill of health, issued before we begin the modifications, will enable this portly beast to handle well and remain stable at speed. Our goal to run the Nevada Open Road Challenge in May is quickly approaching, and a good tight suspension is paramount to our quest for speed.
The Diplomat has a very unique suspension. Unlike those we are accustomed to in our traditional A-, B-, and E-Body musclecars, our Dippy features a transverse torsion bar front end that is rather unique and a bit confusing for the uninitiated. Introduced in 1976 on the new Dodge Aspen and Plymouth Volare F-Bodies, the transverse torsion bar was also the suspension of choice for the M-Bodies, such as the Grand Fury and Diplomat. We contacted Just Suspensions for one of their complete front-end kits, and then contacted Koni for a set of shock absorbers. We dragged all the parts to Sleeper Suspension Development in La Verne, Califorinia, rolled up our sleeves, and dove in. The decision to use Sleeper's facilities to help with this project was made because of Jim Sleeper's vast experience building a variety of race cars for numerous types of racing. Later we'll add trick new Quickor sway bars, and incorporate a couple of other mods to help our Diplomat along on its quest for high-speed stability.
Torsion Tension and Ride HeightUs Mopar guys and gals have always held our torsion bar suspensions near and dear to our hearts. Why? Well, for one, we have the option of raising or lowering our ride height to suit our needs or desires with the turn of a 3/4-inch wrench. The same holds true for transverse torsion bar suspensions systems. That built-in adjustability comes at a price, though, as the raising and lowering of the front end affects suspension pre-load. The torsion bar is simply an oddly-shaped coil spring with a given "spring rate". Lowering the suspension takes pre-load away, causing the suspension to react at a slower rate of speed, while the opposite holds true when the torsion bars are cranked up and the front end is raised. We opted for a lower ride height in order to punch a smaller hole through the air with our vending-machine-like aerodynamics. It's a compromise, but one we were willing to make in the pursuit of top-end stability.