Four Link Suspension, how does it work?

A 4 link allows you to change your instant center. Changing the instant center allows you to tailor how hard the car tries to throw the rear axle down and separate. You do need to know what it currently does. To help visualize, the instant center on a pure leaf spring car is the front spring eye. Moving the instant center in relation to the center of gravity is what you are after. You can mathematically determine your center of gravity, but not REALLY necessary, because you can adjust for what the car is doing. Extending an imaginary line from the bars, where they meet is the 4 links instant center. Move that point forward and down softens the separation. Move that point up and back increases the severity of the separation. You want to get the bars to a setting that is in your shock adjustment window. I tune to the side wall shape. Even consistent bulge.