Again, depending on what you want to do, you need to choose a coil spring rate and anti-roll bar diameter combination to suit your requirements. As Mike Snyder very appropriately said in his autocrossing article, you need to spring the car based on the type of surface and the speed range you will be running. Front spring rates for our cars can vary from 440 lbs./in. (stock) to 720 lbs./in., depending on the application; while rear spring rates vary from 126lbs/in. to 215lbs/in. Most people believe that a coil spring, is a coil spring, is a coil spring. Nothing could be further from the truth and all springs are certainly not created equal. Some things to find out when inquiring about springs are:
- Are the springs cold-wound or hot-wound? If they are hot-wound (and your wire diameter is not ~.700" or larger) then find another spring. Hot winding ruins the heat treatment of the wire, reduces the fatigue life a bit and also produces less consistent springs.
- What wire material are the springs wound from? You are looking for either chrome vanadium or chrome silicon. Preferably, chrome silicon.
- Are the springs stress relieved after winding? This is an easy procedure and is done by most companies so as to almost be assumed. But you wouldn't want to assume now would you??? ;-)
- Are the springs shot-peened AFTER winding? As, most engine savvy people know, this done to rod beams to increase the compressive stress at the surface of the metal. Well, the same is true for springs. Shot-peening is also one of those procedures that is done more often improperly than properly, so make sure to stay with a reputable manufacturer or an aircraft peening operation if you try to have this done yourself.
- Are the springs pre-set after winding? Pre-setting springs is a process whereby the spring is smoothly compressed from both ends until it stacks solid. It is then held at that position for a predetermined amount of time and then released to free length again. Pre-setting is an invaluable process used to combat what is commonly known as "spring sag" or the springs taking a set.
- Are the springs epoxy powder coated? This finish protects the spring from nicks which could cause stress fractures. It also makes the springs look pretty trick as well and you car definitely get bragging rights at the local shindig ;-). Also DO NOT, under any circumstances buy springs that have been chrome plated as this causes hydrogen embrittlement of the spring wire and will most assuredly cause the spring to fail while you are in the middle of your annual trek across the Rockies. As far as I know, no company has been selling chrome plated springs for a LONG time, but it's always better to know about these potentially life threatening things beforehand.
Many members who like the stock replacement springs have had good luck with Moog, TRW and H&R. Some autocrossing members are using Suspension Techniques springs as well. My personal experience has been with Eibach, H&R and Hypercoil. Eibach makes two different sets of springs for the G-body; a performance handling kit and a drag racing kit. The performance kit is part #3803.40. H&R also makes two different spring kits but both are performance/lowering oriented. Hypercoils are widely recognized as the world leading springs at the upper echelon of racing (F1, Indycar, Trans-Am, NASCAR etc.). Hypercoils are also only custom made and you have to do quite a bit of homework before you can get them (since you have to provide them with exact suspension measurements and desired rate at ride height).
Doug
FRom: The Turbo Regal Website.
