When designing the suspension and ride characteristics of most factory cars engineers are primarily concerned that grandmothers won't spill their coffee or complain about poor ride quality. The result is that most stock vehicles are outfitted with extremely soft spring rates that provide a cushy ride quality but offer little in the way of optimized cornering ability or weight transfer. And most don't look all that cool either, unless you're into four-by-fours.
Let's face it; most street machines look better when they feature an in-the-weeds stance. It lowers the center of gravity, gives a better road feel, and makes the car more stable without excessive body roll. However, trying to achieve even a 1- or 2-inch drop while retaining excellent ride quality can be a difficult task, because balancing ride height and ride quality generally involves making some compromises. We've all seen the results of hack jobs that were accomplished by either heating or cutting coils with a factory spring. That's the worst-case scenario-ride quality suffers and you can end up with a car that eats tires for lunch and is dangerously unpredictable on bumpy roads. That's not what you want.
Aftermarket spring manufacturers spend endless hours researching various combinations, which eliminates the guesswork and saves you bucks. So if you've been contemplating cutting or heating your factory coils instead of purchasing a matched set of aftermarket springs, read on to find out how to select springs to achieve the look and performance you want.
How A Spring WorksA coil spring is nothing more than a steel wire that's been wound into a circular coil. Minor changes in the overall diameter of the wire used, the number of coils that are wound, the free length of the spring with no load on it, and the outer diameter of the coil itself all significantly affect the characteristics of a coil spring.
Most springs are rated in pounds per inch (lb/in), which represents the amount of force required to compress the spring 1 inch at its installed height. A spring rated at 500 lb/in will compress 1 inch for every 500 pounds of force exerted on the spring. Compressing the spring 2 inches would take 1,000 pounds of force with a linear spring.
Since all cars will vary in weight, springs will also have various spring loads. To produce a certain spring rate for a specific car, the spring needs to first compensate for the weight of the car itself.
Linear vs. ProgressiveA linear spring has the same spring rate throughout its compression range. Progressive-rate springs have a variable spring rate that increases as the spring is compressed. The advantage of a progressive spring is that it can provide a variable ride quality-softer when the suspension is at a normal ride height, and stiffer as the spring is compressed, such as when the suspension is being pushed hard through a corner.
What Not To DoWhile most gearheads believe that lower and stiffer is better, the majority of suspension manufacturers will argue that it's the exact opposite.
The main advantage of having a car lowered is to increase stability by creating a lower center of gravity, but this doesn't mean it's OK to have your car resting on the bumpstops. With limited suspension travel, the car becomes unpredictable, skipping over bumps and road transitions and causing the tires to lose traction. While stiffer springs promote better handling, there is a limit. Using too stiff a spring will cause the suspension to bounce off sudden jolts. The purpose of a spring is to take a car smoothly over everyday road conditions such as potholes. If the suspension is so stiff or tight that it's not compliant, you'll be looking for a package plan from your chiropractor.
Heating vs. Cutting CoilsDon't heat a spring coil to lower your car. Period. Overheating weakens the spring material, causing unpredictable spring rates that can cause terrible handling manners and sag the car unevenly over time.