I recently got into a conversation with a member here in regards to spring ratings, calculating your FRC, what length springs to consider, the actual rating of the springs in relation to what sway bars you will run and what is the best all around setup for the a Daily Driver that serves as we weekend warrior on a SCCA track. I was in a foreign world. Can someone give us or me some general knowledge of springs, swaybars and coming up with a method of determing what will be good for you. I know alot of us simply copy the setup of someone else and call it a day but I want to know why that setup gives you the results that they do. Thanks

 

Ok, here is what I know:

First, figure out your application and tell us what it is. If you are straight up 100% performance, the answer is easy. RB hollow front 700-800/400-500 lb springs, and a 12-15mm rear sway depending on what springs you pick. Otherwise, you will have to find a compromise.

Since this question is some what generic, We can cover some suspension basics:

FRC-Front Roll Couple- It a ratio between the front roll stiffness and the rear roll stiffness. This pretty much is a simplification or measurement of balance. It's not exactly that, but its pretty close. Obviously there are more factors to balance than roll stiffness (camber, toe, stagger, etc.). So generally we run slightly understeery on the miata so you have extra traction to get on the power. Ironically, I am going to link you BACK to miataturbo for an excellent thread on this topic:
http://www.miataturbo.net/showthread.php?t=62319

Sway bars increase stiffness by forcing both control arms to move together, since the bar is physically connection if one spring compresses, the other does too. Ideally this could double your "spring rate", but of course you will have to read about sway bar behavior on your own. For a generic site, here is a place I visit frequently:
http://www.autozine.org/technical_sc...handling_4.htm

Now, I know you said track and street. Most people will suggest you run something around 500 front and 300+ rear for a mixed setup. I think thats probably pretty good.

I personally like the RB hollow, but some people run the flyin miata 1". I am on the stock sway, but another favorite is the MSM sway bar. Play around with those sizes and spring rates in the fatcat calculator and you will be busy for the next week for sure.