"Leaf springs will always be around in some form or another because they're simple and inexpensive. If you can get the ride height and spring rate you need out of them, then they'll work just fine in most street cars as long as you're not making a ton of power," explains Tom Brown of Heidt's. "However, the only way to adjust the ride height and roll center with leaf springs is by using spacer blocks. Upgrading to an aftermarket four-link system allows changing the suspension geometry and ride height by adjusting the length of control arms and coilovers. Unlike a drag-oriented four-link, street four-links are designed to allow the rearend to roll and articulate, which gives you excellent forward bite and handling. They're the best of both worlds, and usually lighter than a leaf spring system as well."
Due to the impressive appearance of tubular front control arms, you might assume that their chief benefit over a stock unit is strength. However, as Kyle Tucker points out, that isn't necessarily the case. "It's true that the suspension endures incredible loads, but deflection with stock control arms isn't really an issue in most situations, and most people wouldn't be able to feel it anyways," he explains. "The truth of the matter is that it's much easier to manufacture a control arm out of tubular steel than it is to invest in the equipment necessary to make stamped control arms. While the increased strength of aftermarket control arms may be necessary when matched with sticky tires, their main benefits are improvements in suspension geometry."
Typically, the mounting points of the control arms and ball joints must be moved to achieve any appreciable camber gain. For the most part, these anchoring points can not be changed without seriously hacking up the frame or compromising other aspects of suspension geometry, such as the Ackerman and tie-rod angles.
"Front suspension design is the most sophisticated system on the entire car. Everything is interrelated, and you can't change one thing without affecting something else," Chris Alston explains. "Properly designed control arms can slightly improve the camber curve and move the caster angle, but to really make a difference you have to move the pickup points." Furthermore, the built-in shock mounts offered in most aftermarket control arms eliminate the need to modify a stock arm when converting to coilovers.
For those with well-endowed bank accounts, a new front subframe assembly is the pinnacle of suspension upgrades. Although quality aftermarket components bolted to a stock subframe will get you 90 percent of the way there, an aftermarket clip offers just a wee bit more performance-and looks trick to boot. The limitations of how much factory suspension geometry can be tweaked are no longer relevant with an aftermarket clip, as the mounting points of the control arms, tie rods, spindles, and coilovers can be positioned wherever a suspension designer chooses. "By starting with a clean sheet that doesn't force us to work within the constraints of the factory design, we can move all the suspension mounting points to improve the camber gain and caster while eliminating bump steer," Tom Brown explains. "Additionally, aftermarket clips provide more room for bigger tires, and can be setup with a variety of motor mounts to simplify engine swaps."