SPRINGS
In a very basic view of the suspension system, the springs support the weight of your car, control the ride height, and absorb the vertical motion from running over any bumps or uneven surfaces. They do this by storing the energy that was used to compress them (from bumps in the road, for example) and then releasing it back into the car in a controlled manner thanks to the dampers.
SUSPENSION SPRING RATE
The spring rate, usually referred to in lbs/in (though you’ll also see kg/mm), dictates how much a spring will compress depending on the load applied. For example, a spring with a linear rate of 250lbs/in simply compresses one inch for every 250lbs load applied to it. So a load of 125lbs will compress it 1/2in and a 500lbs load will compress it 2in.
A spring with a progressive rate gradually gets stiffer as the load increases, so a 150/500lbs/in spring will compress 1in with a 150lbs load on it, but may need 250lbs to compress the next inch and then 400lbs for the third inch until it reaches 500lbs load to move another inch.
Looking at it the opposite way, as the load
