Sometimes when we start putting springs on the tester it gets to be a real laugher at what the springs test out at vs. what they are actually rated at... Out of the box I've seen them off by as much as 40 lbs!!! As for the rating suggested for a particular car, remember that it also has a lot to do with front to rear weight and the angle the unit is mounted at. Looking at just the total weight of the car and picking a spring based on that can lead to errors in the spring rate. Whenever possible, I put the car on the scales and check the weight front to rear and side to side. Depends a lot on where components are placed as to how the weight is distributed on the four wheels... Good thing is that all the reputable vendors will exchange the coil over springs for a different rate as long as they haven't been beat up too bad during the install.

Now if I ever come up with an extra $6k for a shock dyno I can really waste a lot of time playing around with the stuff everyone else takes for granted!!!!!