Progressive rate springs are wound with the bottom coils somewhat close together and as they move up toward the top, the coils are wound wider apart. The top part of the spring gives you a little more flexibility in that they move a lot thereby giving you the ride comfort. The lower part of the spring helps to ensure that the load does not bottom out the car.
If you get springs, only get progressive rate springs for a daily driver. For drag racing, you'd want linear rate springs where ride comfort is sacrificed for holding the car straight with minimal movement in wheel to fender variances. In other words, they're only there to handle slight bumps, as welding your axle to the rest of the car isn't an option.
When you lower your car, progressive rate springs are obviously shorter than stock, so you will NEED that ride comfort factor, as the spring has less vertical movement now. Although they try to build in a better ride with the progressive rate, they will always give you a harsher ride than stock just because they are shorter.
A lot of people like the look of a lowered car, just to close up the wheel well gap, but you will also notice, with the proper setup, that your car will handle like its on rails!
As far a shocks and struts go, you have to replace your stockers as they won't last very long on a lower car. If you have the cash, you can get the Tokico adjustables where you can dial in to one of five ride settings from soft to hard. I went with the non-adjustables, which are set to the middle setting of the adjustables. I'm perfectly happy with them.
If the roads in Pittsburg are crappy in some places, you won't want to lower your car any more than 1.5" so take that into account when picking out a set of springs.
To see a really crappy setup, put "The Fast and The Furious" DVD in and find the spot where a bunch of rivers drive up to the shop where the undercover cop works. It's the scene where they come in and order a bunch of stuff and the Hispanic guy pulls out a wad of cash to buy 5 of everything on his list. Watch the lead rice mobile as it drives up to, and parks at the curb out front, it's slammed to about a half inch of clearance. As he’s driving notice how the body of the car is absolutely rocked to its foundation as he drives. The driver will soon be helping to build an addition onto his chiropractor's house, or will soon become sterile with his balls knocking together all the time!
