The Big Compromise
For 99 percent of us, a well thought-out neutral system (24- to 36-inch-long bars with an IC around the front bumper) would offer some really good performance. It's the 1 percent who are looking for every last ounce of performance that would need to start worrying about instant center and roll steer. So how should you set up your suspension to do what you want it to? First off, understand that you cannot have a system that does everything the best. You have to find a compromise. For example, an independent suspension can handle better and drive smoother than a straight-axle rear suspension. But, a straight axle will launch harder and withstand higher power from the engine.
Here are some basic starting points: If you're building a long-travel off-road truck, then bars up to 48 inches long and an IC a few feet in front of the truck is best for neutral handling throughout the entire 2-plus feet of travel that you might need. On a road-race truck, shorter link bars with a low roll center and extra attention to roll steer would be a good place to start. And for drag racing, a two-link would work well (there's no cornering in drag racing) or a four-link with 18- to 24-inch-long bars and an IC that's in the middle of the chassis and 6 to 10 inches from the ground. Understand that these are just basic starting points. The dynamic relationship between the ground, tires, rearend, link design, and chassis is constantly changing, and we can only hope to find a fair compromise that works well for what we're trying to accomplish.
Finally, before settling on a suspension design, be honest about what you need your truck to do, not what you want it to do or how you want it to look. We all want our trucks to be the very best, but the actual use of your truck should be considered in your suspension design. If you want a truck that can put 1,000 hp to the ground using a limited-travel suspension design and still be able to drive it to work every day, you're going to suffer with an ill-driving truck in most situations. The same goes for a daily driver that has too much suspension travel-it just won't drive very well that way.