Currently running Stance coilovers on my 2000 coupe with C6 Z06 sways, metal end links, all OEM rubber bushings and 275x30x18 (9.5 inch wide) front and 325x30x19 (12 inch wide) rear wheel/tires. The Stance coilovers came with their standard springs which are rated at 420 lb front and 560 lb rears. Stance now offers spring upgrades to Swift springs in varied rates. I don’t have any issues with the ride or handling of the current springs but was considering the upgrade based upon the claims of lighter weight and longer spring life (though I still will decide if the standards don’t already fit my needs as is).

All of the above aside for a moment, the question that I am looking for information on is how to ultimately determine optimum spring rates for the coil overs?

In researching I have come across the antidotal, “this worked for me” type of answers (and there is nothing wrong with that as it is real life experience), and some detailed calculators based on suspension geometry and weight etc.

The one thing that stands out is whether to include the sway bar size in determining the spring rate, or not. One school of thought is that the springs should be based solely on carrying the load, if you will, and ensuring the wheels remain in constant contact with the surface and not used to impact or tune roll. (So you may have a softer rate spring to ensure contact and then tune roll with bigger sways.)

The other school of thought is that you combine the springs in trying to tune roll as well. (So you may use a stiffer spring to control roll in combination with the sways. But suffer the harsher ride and possibly lose contact on uneven surfaces.)

Looking for some insight from those more experienced. Thanks.

 

I can tell you that when I was in the suspension design business for one of the big 3 (many years ago now), we would initially try to home in on the spring rates and shock settings to get the ride setup with what you might call a "nominal rate" sway bar. sfter that it was a process of playing with all three components until we got the desired result.

Some years ago, there was a well documented "shoot out" between a couple of F-body chassis guys - one (Herb Adams, IIRC) believed in fairly soft springs with stiff bars and the other (name lost...) used pretty much standard bar rates but cranked up the spring rates. They both ended up with very similar circuit lap times, although I seem to recall the testers preferred the soft spring/stiff bar approach.

I think I would start on your path by finding out what the effective wheel rates are for the OEM leaf springs, then the same for the coilovers. Note wheel rates, not actual spring rates - wheel rates are what are important. Then decide do you want softer or harder compared with say the Z51 or Z06. I would not mess at all with the front to back stiffness ratio. I would take the view that Chevy knew what they were doing in setting rates.