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

SOURCE
Bill Buck Race Cars
10816 Motheral Drive
Austin
TX  78753
512-837-4999
www.billbuckracecars.com
Competition Engineering
80 Carter Drive
Guilford
CT  06437
203-453-5200
www.competitionengineering.com
Strange Engineering
8300 North Austin Avenue
Morton Grove
IL  60053
847-663-1701
http://www.strangeengineering.ne
t
Rock Auto
6680 Odana Road
Madison
WI  53719
866-762-5288
http://www.rockauto.com
Unisteer Performance Products
AK
800-338-9080
www.unisteer.com
Anthony Jones Engineering (AJE Racing)
6235 N. Co. Rd. 275 W.
North Vernon
IN  47265
812-346-7356
www.ajeracing.com