Why don't I just cut my existing springs?

1. Many aftermarket lowered springs are designed to be just captive (held in place) with the wheel at full droop. This is a legal requirement throughout Australia. Cutting off a portion of the coil will reduce the free height (length of the spring out of the car), possibly to the point making the spring loose at droop.

2.Most springs are designed to a fairly tight tolerance of material volume to load carrying capacity. That is, the amount of steel used in the spring is just enough to hold up the car over the life of the vehicle with normal use. Chop off some coils and you've dramatically reduced the amount of material, which almost always will lead to an overstressed coil that will sag prematurely.

3.A reduction in ride height is normally coupled with a proportionate increase in rate to offset the reduced bump travel. We need to slow down the compression of the spring enough to make sure we don't punch through to the shock at high velocity. A properly designed lowered spring will have a rate increase sufficient to offset this bump travel reduction.

4.The cutting method can also be a problem. Generating heat is not so much a problem as reduction in the heat afterwards. That is, heating the material beyond its temper and then rapidly cooling it will affect the composition of the material.Iirrespective of what tools you use, its not good practice overall.

Lowering a vehicle by modifying the suspension system should generally
comply with the following guidelines:

a) Cutting, welding, heating or bending of any suspension component is
not permitted.

b) Coil springs must be securely mounted so there is no lateral
movement when the suspension is fully extended.

c) A recognized spring maker must carry out any resetting of springs.

Oh grow up everyone. There have been thousands of springs cut over the years including mine I think by a professional suspension business. So long as your struts support the spring there is no danger. If you have worn standard struts then there is definitely a danger. Since modern springs are variable rising rate then you will find it best to replace with new ones of the height you require. Old cars eg Kingswoods didn't have rising rate springs and the simple swap was to fit cut down V8 springs to 6cyl cars to improve handling and appearance.