From Chassis Engineering. While it is a very basic book when it comes to suspension design, its still much more of an authority that cutting springs is OK than the guys ranting above.

 

I don't think you understand how spring rates work. The formula for coil spring rate is as follows:

Rate = Gd^4 / 8ND^3, where
G is the torsional modulus of steel, d is the wire diameter in inches, N is the number of Active coils, D is the coil diameter in inches.

Notice length of the coil does not have a factor in its rate.

To have a variable rate spring, you have to change the diameter of the spring (conular shape), or change the diameter of the wire along its length. The coil shown is not a variable rate spring.

The fully compressed coils sown in the picture are inactive, since they are fully compressed even at full suspension drop. Since inactive coils don't affect spring rate, they can be removed.

 

I can't remember all the factory springs I've replaced, from all the various manufactures, that were broke at the last coil. It's a common failure point anyways.

 

But length is directly related to the number of active coils. Removing dead coils will reduce the number of active coils because the pre-load has to go somewhere. In the equation above, that decreases N and results in a higher overall spring rate.

If the spring had dead coils at its free length, then removing them would not change the rate.

 

Figuring the length of the wire made into the spring is built into the equation. The free height isn't an issue if that is what you meant.

You can have a variable rate spring by having more coils per inch in one section of the spring. That spring is a variable rate, it just has such a soft section it goes into coil bind at a very low load. Not a useful variable rate for road holding but its still a variable rate.