Originally posted by cliffjohnson:
not to sound like a dumba$$, but what do you mean by linear and progressive?


Hey, never hurts to ask.

Progressive rate = The rate goes up as the spring gets compressed. This means it might take 150lb to compress the first inch, then 200lb additional for the next inch, and 300lb additional for a third inch. Grand total 650lb of pressure before 3" of compression travel is attained. Those springs usually have an uneven coil separation when you look at them... more spaced at the top and tighter at the bottom, or vice-versa.

Linear rate = The rate is constant through the whole compression stroke. First inch could take 200lb, and it's gonna take increments of exactly 200lb for every other inch of compression you're adding. Those springs are usually wound in an evenly spaced manner.

What this means in the real world is that a progressive rate spring will easily compress itself to soak up road irregularities and small bumps. Then it doesn't need too much damping to be controlled and the ride stays comfortable. When you corner (lean) or hit a big bump then the soft portion of the spring gets compressed and the stronger portion "catches" the car. It's more of a "road" setup. A linear rate spring on the street will need a LOT more damping otherwise it'll feel harsh. But you don't have to "lean" the car in forever before getting into the stiff stuff. They're also better to control brake dive and acceleration squat.

BTW.. most people don't think about their tires when they "review" a suspension.. They make more of a difference that you think. A 15" wheel with a nice all-season tire will absorb road irregularities and minor bumps.. but it bounces back so they work well with a soft suspension to control the bouncyness... Ever seen a CASE backo driving down the street?? Bouncy tires, NO suspension... That's akin to fat tires and a stiff suspension. Baaad.

Opposite goes for thin and stiff sidewalls. Slap a set of 18's on a stock suspension and the rolling stock sends sharp jolts that the dampers can't control. The car feels harsh and rough. Add better dampers though, and then it comes into its own.

The whole car is a system.. try and set a goal for what dynamics you're after, and make sure the parts you slowly add are helping toward attaining the goal, and not counter-acting each other.

..the goal might be looks with no regard to performance, and that would be fine too. Then you can run slammed ground controls on stock struts and shrug off the comments from those of us who track our cars. It gets very personal.

This is turning into a lesson.. Happy motoring everyone.

- Pascal 1998 Ford Contour SVT - SOLD!