One last factor to consider is the angle of the spring and shock relative to the control arm. Mine is 15 degrees from vertical, which calculates to a correction factor used by QA1 of 0.93. Divide the spring force (1,571) by that correction factor to determine the adjusted spring force (1,689 in my case). Based on that figure, QA1 could recommend a spring rate best suited for my car, which would be the 550-lb/in springs I already installed. See how sometimes it’s good just to trust what guys who do this for a living recommend? By the way, the process for determining the spring rate for the rear suspension would be the same. Instead of cutting the rear springs, I should have called Eaton Detroit Spring with specs for the rear suspension. Eaton can make custom springs, and the cost isn’t much more than buying a pair of off-the-shelf springs.