I want to modify the coil springs in my car to lower it 1" without raising the spring rate, so simply trimming the overall length is not an option. My idea is to remove material from along the top edge the active coils. Obviously, making the rod diameter smaller will make it weaker so it will compress more under a given load. This is where I will get my lowering. I want a progressive rate, so I'm thinking I should remove material only from the first one or two coils. In my head, this will yield a softer ride for normal driving on average highway irregularities when the spring is being compressed those first 2 inches or so. Yet, it will be more resistant to the compression when under more load, such as on larger dips/humps and/or when the vehicle is loaded more.
So, if I were to remove material from the spring:
(1) Will the spring compress more and lower the car without increasing firmness?
(2) Will I actually get a progressive rate if I remove the material as described?
(3) What would be the difference between removing the material from, say, one coil versus spreading it along two or even three coils? (The spring in question has 5 active coils)
Disclaimer: I would remove material with a flap disc for better control and to minimize heat and to create a smooth surface to avoid stress risers. I would also gradually taper in and out of the maximum amount removed from the coils instead of immediately digging in at the start and finish of the modified areas.
