What about the steeda sport springs? Better than the pro kit?
Hi matt,
Steeda "Sport" Springs are just a softer version of Steeda's "Comp" Spring which are not all that firm in the real world. All of Steeda's springs are linear rate springs. A linear rate spring needs the same amount of force to compress the spring one unit of measurement which in the USofA is usually expressed in inches.
A progressive rate spring is different and is usually designed to be softer initially. At some point in being compressed a progressive rate spring will suddenly increase in spring rate as the softer spring coils go dead due to being coilbound. At this point the looser wound coils remain active and effectively become the new higher spring rate.
The trick with a progressive spring rate design is to get the car riding at the desired ride height and as soon as any additonal load is introduced to have the spring go into the higher rate. This is extremely hard to do in the real world because the spring makers have near zero control over the loaded weight of the car on either end. For example if you installed a supercharger and used the normal version of a progressive rate spring your car would sit lower and have a poor ride because you are sitting on the bumpstops almost all of the time. You used up what little bump travel you had due to the extra weight of the supercharger.
Ah, you say but the higher spring rate should have kicked in to keep me off the bumpstops. Here is progressive spring rate nasty little trick number two. With the reduced ride height you need the higher spring rate to kick in immediately to keep the car off the bumpstops because once the suspension is compressed this far it immediataly ruins ride and handling. The problem is that no spring maker can build a spring to handle all weights of car based on the equipment installed.
Think about it for a moment. As a spring maker you would need a spring for every year and every model with every option combination even simplifed it would look like this: 2005 V6, V6 with Thumper1000 sub, V6 verts, V6 verts with Thumper1000 subs, V8, V8 with Thumper1000 subs, V8 verts, V8 verts with Thumper1000 subs, V8 supercharged, V8 supercharged with Thumper1000 subs, V8 supercharged verts on and on and on... Then we would need to do it all over for 2006, 2007 , 2008, 2009 on and on and on to make the springs actiually work as advertised.
I have an s197GT 5-sp coupe with almost every option except the Thumper1000 amps and sub. When I installed the FRPP/Eibach ProKit springs on the car I was initially happy with the springs because the car felt more planted. But the ride was not very good and the car still had brake dive and rolled quite a bit which surprised me. So as time passed I found other issues with the springs but for the most part they were O.K., not great but O.K. I also got to install them on other people's cars some with blowers, some well equipped GT's, some autos and one very stripped w/zero option 5-speed GT. This is where I was surprised, the blower cars were terible with D-specs and bottomed all the time but on the cheap 5-speed GT the springs worked better.
So what does Eibach probably the largest aftermarket performance spring maker in the world have to offer? Just four different springs to cover all V6 and V8 coupes and verts, that's it! So how do you think they are going to work? I can tell you, they work sub-optimum, they work O.K. but not where they could or should. They are disappointing because they are a severe compromise and cannot actually work very well for any of these cars because they cannot control the weight on each axle.
The problem with the ProKit springs can be boiled down to this; too low and too soft initially without enough spring rate soon enough in their travel before hitting the bumpstops which they always are doing. So on a spring testing machine I measured and found the real issue. By the time the ProKit springs upper spring rate is actually the working spring rate the front struts are almost totally already bottomed out and going soilid (mechanical interference, metal to metal). Same problem at the back of the car between the rear frame rails and the axle top bumpstops.
Eibach ProKit springs measured initially a very soft 175lb/in and increasing up to a great 239lb/in just as they hit the bumpstops and keep rising to peak at 249lb/in near coil bind. This is just too low a spring rate for such a heavy car with such a big drop in ride height and by the time the spring gets to a good rate it's all over and bottoming out. This is obviously a ride and handling killer.
Steeda Sport Springs measured 200lb/in in front and 175lb/in at the rear. Steeda Comp Springs measured 225lb/in in front and 185lb/in at the rear so you can see there is not a huge difference in spring rates. Compare the Steeda spring rates to the stock spring rates which are 136lb/in in front and 141lb/in at the rear. The factory Ford race cars are significantly lighter than our street cars and they are shipped with basic spring rates of 500lb/in front and 300lb/in rear, that's the starting point.
So after my spring rant here is the last bit about springs you need to know. Linear rate springs are much easier to find good damper rates for than progressive rate springs. Figure it out. With the spring rates moving up and down what do you set your dampers up for? The hard end of the rate which kills your ride or the soft end which would have you bottoming out even worse and make the car feel like it is not handling right?
The lesson to learn here is that you cannot take away ride height without a large increase in spring rate or you get poor handling and poor ride. There is a trade off that MUST be made for every chassis and you have to decide what is important to you. For most cars (and for the s197 chassis absolutely) you need to choose one, and realize two are possible with some compromise but you can never have all three optimized. Ride, ride height, grip/handling.
HTH!
