Nissan 240SX - Performance
Springs, together with anti-roll bars, have a significant effect on the feel of a car and its responsiveness to steering input. Increasing spring rate at a particular corner of the car transfers more weight to that corner making it slide more. Hence, if your car is understeering, you can either decrease front spring rate or increase rear spring rate to correct the condition. You can increase front spring rate and decrease rear spring rate to correct oversteer.
Installing lowering springs on your car can provide a substantial improvement in handling. The center of gravity of the car will be lower, which will allow the four tires to stay more evenly planted to the ground. Lowering a car is more involved than just installing shorter springs. It is usually necessary to readjust the camber on the front and possible the rear suspension since it will change when the car is lowered. Generally, a car should have a full alignment after lowering the suspension. Although lowering a car will usually improve handling, lowering it too much will not allow for enough suspension travel, or stroke. The car may bottom out on the suspension (suspension reaches full travel) or the chassis may actually hit the ground, leading to loss of traction and possible damage to the underside of your car.
When lowering a car, you must consider what type of driving conditions the car will see and what spring rates are appropriate for you. If you significantly lower the car, you will need stiff springs to limit the suspension travel and prevent bottoming out. Also, if you plan to race on bumpy surfaces or do mostly street driving, I recommend avoiding a suspension setup with very small travel. You need a fair amount of suspension travel to absorb bumps. If you make your suspension too stiff because you have very little suspension travel, then small bumps will tend to lift the wheels off the ground instead of being absorbed by the suspension. If the car bottoms out, it will experience a sudden loss in traction that can easily lead to a spinout or crash. Therefore, on bumpy tracks, use softer springs and greater ride height to improve handling and avoid bottoming out.