1993 Ford Mustang Notchback - Shift of Power

When it comes to extracting ridiculous power out of a big-block, it's so easy a Wall Street CEO could do it. Nevertheless, that easy grunt comes with the penalty of extra mass, which makes transferring all that power and weight to the rear tires even more difficult. The trick is to offset the increased heft over the front tires with lightweight suspension components, and to optimize the spring rates to facilitate quick and efficient weight transfer. By installing a complete tubular front suspension system from Anthony Jones Engineering on Project Fox, our goal is to accomplish just that.

For those coming late to the party, the goal with our '93 Mustang project car is to run 9s in street-legal trim on a budget of $25,000. To prevent Project Fox's 775hp big-block Ford from pulverizing its 275/60R15 drag radials, we installed a complete Competition Engineering rear suspension system last month. That said, planting the rear meats is impossible unless the front suspension pulls (or shifts) its own weight, so on this go-around, we'll be installing an AJE tubular K-member and lower control arms, coilovers, and adjustable camber/caster plates. Further assisting with shifting the power rearward are Strange single-adjustable shocks, and a lightweight Unisteer manual steering rack. Together, these components will help shed nearly 100 pounds off the nose of the car. That's definitely a good thing, since we estimate that our aluminum-headed 532 big-block weighs roughly 150 pounds more than the stock iron-headed 302 small-block.

Transferring weight, however, is just the first part of a front suspension's multiple roles. As soon as the car leaves the gate, the front underpinnings are also responsible for directing man and machine in as straight of a path as possible. Light steering feel and side-to-side wandering are the bane of a well-handling drag car, but fortunately AJE's suspension features a wide range of alignment adjustments to dial out any potential drama. Showing us how to set it all up once again are the generous folks at Bill Buck Race Cars in Austin, Texas. Since Project Fox's stock motor and trans had been pulled long ago, the entire aftermarket suspension bolted right up in half an afternoon.

Drag vs. Street Caster
Caster is simply the angle of the front spindle when viewed from the side of the car, and straight-line machines and corner carvers call for vastly different caster settings. A spindle that tilts rearward has positive caster, while a spindle that tilts forward has negative caster. Since light steering and wandering is a consequence of negative caster, almost all production cars have a few degrees of positive caster built-in from the factory. Where road cars and drag cars differ is in the amount of positive caster that's desirable. "The greater the positive caster, the better the car's straight-line stability and the more effort it requires to move the steering wheel," Bill Buck says. "These aren't necessarily bad things in a drag car, so I like to set caster at 5 to 7 degrees in straight-line applications, however, heavy steering effort isn't ideal for a street or road race car, and the wheel can have a tendency to jolt when you hit a bump with too much positive caster. Consequently, you want to limit positive caster to about 2 degrees in these types of applications, which makes the car feel more agile while still providing enough straight-line stability."
-Stephen Kim

Drag Springs
Regardless of how fancy a rear suspension setup may be, without the correct front spring rate it will never put the power down. Bill Buck says the ideal front spring rate for a drag car is just enough to hold the front end up in the air. From there, it's up to the shocks to fine-tune the rate of weight transfer. Furthermore, choosing the correct front rate is far more important than choosing the correct rear rate. "The lighter the front spring, the more weight it will transfer rearward when you hit the gas. Since springs with lower rates squish down more when loaded than stiff springs, they store more potential energy," he explains. "You can use stiffer springs to prevent the suspension from bottoming out, but that can hurt weight transfer, so I prefer using softer springs and travel limiters. If a car transfers too much weight and does violent wheelstands, then it might be necessary to use stiffer springs. If Project Fox was a track-only car, it could get away with 170 lb/in springs, but since it will see some street time a 200 lb/in spring is a better compromise. AJE's coilover conversion relocates the spring right on top of the ball joints. That means that the spring rates and wheel rates are very similar, which allows running a relatively soft spring."
-Stephen Kim