spring rates

hello guys,

what exactly does "spring rate" mean ? and what do the numbers represent in terms of measurements ?

Spring rate refers to the amount of force needed to compress the spring a certain distance. The measurement given in most JDM springs is Kg/mm, which as you would expect, means the number of Kilograms needed to compress the springs by 1 milimetre. The higher the rating, the stiffer the springs are going to be. This will affect the amount your springs will compress during hard cornering.

But stiffness is not the be-all and end-all of Driving Comfort... Driving comfort is also affected by the damping rates of your shock. If the 
shock is very stiffly dampened, then it will stop the spring compressing during sharp shocks - i.e. when you hit a bump. Underdampened shocks will not be able to control the oscillations of the spring after hitting a bump, and you will get the bouncing effect those ricey cars tend to have

So, if you have stiff springs, you should have stiff shocks to match. That way you will have minimal bodyroll, and minimal bouncing

If you have soft springs with stiff shocks, you will still have bodyroll, but bumps will feel like shit

If you have stiff springs with soft shocks you will have minimal bodyroll, but you will feel bumps more because the car bounces a few times after the initial bump


Does that help?

thanks dominik, as usual you are always helpful.

so it doesn't matter what "height" the spring is ? so one spring can have the same spring rate as another spring that drops a car by 3 inches (3 inches shorter) ?

Yes it is possible. 

But because the shorter spring will position the shock absorber closer to the end of its travel (the bumpstop), its not a good idea to have the same spring rate with shorter springs - because while its fine to allow 3" of travel with stock height, allowing 3" of travel at a lowered height will most likely bottom out the shock or allow the wheel to make contact with the fender