What's the difference in "Progressive" vs "Specific" rate lowering springs?

[lx5091]

Progressive rate springs have bigger gaps between the coils at the top and bottom and smaller gaps in the middle. What this does is allow the spring to compress alot in a slight lean or over bumps, but the more force that gets applied to the spring such as a hard corner, the stiffer the spring gets because you start to compress the tighter coils. These are good for someone who is anal about keeping good ride quality, but wants "a little" more performance. This setup allows quicker turn-in than stock, but is still not really considered "quick" turn-in. Turn-in is the immediate controlled RESPONSE during a corner, like if you are going straight and suddenly pull the wheel on an autocross car it will "turn-in" very fast while being accurate and the same speed left turn in a '53 buick the right side of your bumper would scrape the ground, VIRTUALLY having no turn-in.

Specific rate springs have coils which are evenly spaced these provide very fast turn-in, but don't "absorb" as much of the road and unfortunately are a little harsh over even small cracks.

got it? good. Now go get some 650 lb specific rate springs!

kidding, that's just what I bought altough I haven't yet installed them.