Calculating the optimal spring rate for any car can be expressed in the following equation, where "F" is the free length of the spring, "L" is the loaded length of the spring, "R" is the baseline ...

Read about Coilovers and the different tyeps of springs such as Progressive Coils and Air Ride Technologies ShockWave inside Rod & Custom Magazine.

We can do a calculation similar to that of the front-wheel rate to find the effective spring rate. In most cases, we see about half the effective rate as the installed spring rate.