Leaf springs are like iron cylinder heads. You can get them to work reasonably well, but unless class rules require you to run them, far more effective solutions are at your disposal. This explains why you won't see leaf springs beneath many front-running Pro Touring machines at a Goodguys autocross event. For g-Machines that must excel in both on-track performance and around town comfort, rear four-link suspension systems are where it's at. For a very reasonable price, they offer incredible improvements in handling, braking, and forward bite without sacrificing ride quality. Detroit Speed and Engineering has been offering four-link conversion kits for Camaros and Novas for several years, helping its customers stomp quite a few Mustangs around the autocross. It didn't take long before Mustang owners wanted to level the playing field, and began asking DSE to build parts for their cars. The company responded with its revolutionary Aluma-Frame front suspension system, and to ensure that the back end could keep pace with the high-tech frontend, DSE simultaneously engineered an all-new four-link rear suspension setup for 1964-70 Mustangs.
Considering leaf springs have been around since the days of the horse and carriage, it's somewhat miraculous that they're still chugging along hundreds of years later. A set of modern performance leaf springs matched with quality shocks make for a very cost-effective street combination. Furthermore, thanks to modern tire technology and traction-enhancing electronics, drag cars are now running 6-second e.t.'s on leaf springs. Even so, the biggest drawback of the typical leaf spring suspension in a muscle car is that the springs also serve as the control arms. That means that the springs are forced to endure all the acceleration, braking, and cornering loads of the rear suspension by themselves. This can lead to wheel hop during acceleration, and brake hop under braking, as the big and heavy rearend wraps up under load. Stiffer spring rates help resist these forces, but adversely affect ride quality.
The ideal solution to the problem is adding a set of control arms to assist in locating the rearend and support it when under load, which is precisely what a four-link accomplishes. Furthermore, replacing the leaf springs with coilovers yields much greater adjustability as well. For Mustang owners ready to take the plunge, DSE's QuadraLink kit includes a set of tubular upper and lower control arms, a Panhard bar, a sway bar, coilovers, a floorpan crossmember, and all necessary mounting brackets and hardware. Installation shouldn't be all that difficult for a seasoned veteran, but it does require some basic welding skills. To get a firsthand look on how it's done, we watched closely as DSE installed the QuadraLink on its 1966 Mustang fastback project car.