Potong Spring
by Adian Yein Khalid

Actually, cutting springs if you are on a budget, contrary to popular belief, is OK, and a much better option than certain examples of lowering that I have seen such as heating up the coils and compressing them!! Springs must never be put under a blow-torch, as it will result in the metal properties breaking down and the springs losing their firmness. If you do intend to lower your standard springs, just cut them with an angle grinder.

Cut springs are actually harder than std springs!
Why? The Coil Rate is the same, but the less number of coils in a spring, the harder the spring (Spring Rate increases). It doesn't make sense but its true. The equation, in words, is something like:

Spring Rate= (Gd^4)/(8ND^3)

G = torsional modules for steel = 11.25x10^6 or 11,250,000
d = wire diameter in inches
N = number of active coils
D = mean coil diameter
8 = a constant for all coil srpings

So in words, Spring Rate is the the function of the torsional modules for steel and wire diameter to the power of 4, over the coil spring constant times number of active coils times mean coil diameter.

- this formula only works for linear rate springs.
- to determine the number of active coils, count only those that can move.
- coils that are resting on mounting plates do not count as active.
- wire diameter can be acurately deterimined using a caliper
- mean coil diameter is achieved by measuring the outside and inside diamater of the coil spring from above.
- torsional module only works for steel, other materials such as titanium requires another factor.

If thats difficult to understand, lets just say that Spring Rate = wire diameter of coil / number of active coils X mean coild diameter.

So, look at that equation: the number of coils in the spring, as the denominator, means that the less coils in a spring, the harder it is.

BUT....

When you cut a spring, you must think about:
1) Less travel before the shock absorbers hit the bump stop. You don't want that for a road car, handling gets erratic when the suspension bottoms out (spring rate hits infinity!). By the way, never discard the bump stops as bottoming-out without bump stops harmst he suspension more.
2) Another set of standard springs for when you sell the car
3) Can your standard absorbers cope with the increased hardness of the springs?
4) And, cutting springs means that you don't have total control over the height. Cut too much, and you cant put them back!
5) Never lower your car more then 2 inches, maximum. More than that and the geometry changes drastically, and you car will handle worse, resulting in what is known as roll-oversteer. Excessive lowering also results in your CV joints suffering increased wear.