[mfain]

I designed my own suspension for my 56 Corvette road race car, but it is based primarily on C-4 components/geometry with coil-overs. The following is my opinion after going through the drill (4 different suspension configurations). First, you need to balance the roll resistance front to rear. Two primary factors are the roll force (simplified -- the weight at a given end of the car times the lateral g applied at the center of gravity at that end of the car) and the moment center at each end of the car. If you left the geometry on your suspension the same as it was in a C4, then you can compare your car to the C4 and make an estimate on the spring rate differences. Your car has a higher front weight percentage than a C4, and the center of mass is probably a little higher. This would imply a need for a higher front spring rate than a stock C4 if you used the same rear spring rate. You may have noticed that newer Vettes (and the Viper) have gone to much higher spring rates in the rear. This is becaused they lowered the rear moment center, requiring a higher spring rate to produce the same roll resistance. This makes the rear tires do more work with a side benefit of reducing rear camber gain which keeps the wide rear tires flatter on the ground during acceleration. You might also have noticed that the Sprint Cup guys put on an outboard track bar adjuster that allows them to really lower the outer end of the bar -- this lowers the roll center on a straight axle rear end set-up and allows them to adjust the rear roll resistance in a hurry. If you changed any of the C4 stock geometry (track width, height of the suspension pick-up points, etc) then your best bet is to spend about a hundred bucks on one of the basic suspension geometry computer programs, enter your car's data, and let the computer due the calculations (moment center, roll resistance, bump steer, etc). Grassroots Motorsports Magazine has several programs listed. Once you get in the ball park, you can fine tune with front and rear roll bar sizes -- the bars also contribute to roll resistance.

I know this got a little complicated. That's why I recommend a computer program. As far as shocks go, I used AFCO coilovers for the initial set-up because they were fairly inexpensive and can be modified easily. Once I get where I need to be, I will switch to Penske or Ohlins shocks. You might want to contact one of the Corvette race suppliers (Guldstrand) for recommendations on your spring rates.

Good Luck

Pappy