Yet another spring rate thread
 

So, for a subject that has been practically beat to death, it's hard to gather information for what I need. I've got a set of Koni sports, GC collars and FM top hats in the rear. I need springs, but my budget is calling for something like QA1's. Some autocross and somewhat daily driven, but I drive it hard on the street when I do. The QA1's only come in 50lb incriments, so I was thinking of 400/300 to be a good midrange, but I might lean towards 450/300. I do favor oversteer to understeer. I'll probably run a RB solid front sway. I don't claim to fully understand all of this, but I have a general idea of lower BF = smoother ride and higher FRC = more understeer. Anyone care to throw in your 2 cents?
On the FCMS site here are the specs using the 19mm/12mm solid sways.
400/300
BF - 1.09
Roll Stiff - 2,295
FRC - 48.8%
450/300
BF - 1.03
Roll Stiff - 2,411
FRC - 51.3%

fwiw I love my set-up and have been successful with it.
I have koni/gc with 650-450 and rb hollow with stock rear.

That's pretty high rates. stock sports or race revalved? how many miles do you have on that setup?

FWIW, 600lb springs in the front of a miata are pretty much awesome on the street... amazingly not bad, its the rear rates that can really nuke ride quality. Of course, you gotta have the right shocks for it to ride well, but I promise its nothing like a civic slammed on cut springs.

I've got Koni sports w/ 30k on them, I don't know how much spring they can handle

koni sports are yellows right? I think off the shelf valving is good for around 750.

Koni RACE maybe. Koni sports are good for 450/300 MAX.

I run 400/250 with no rear bar. I'm putting the stock bar back on this weekend, too much push.

yep yellows. so I'm getting the idea from many sources that rear rates really make the difference. I've heard of people loving a 450/250 setup, which brings the bounce frequency down, but really raises the front roll couple. I don't know in roll couple where the neutral line is between over and understeer. I'll be hitting the 250hp range soon, so that might cause a little oversteer of it's own. the opinions vary, so I'd like to know what you noticed (vs) stock with your setup?

750/450 with Afco's. RB sways, soft in the rear, med in front.

my problem is turn in right now. It feel very neutral and I can stomp the gas around corners, but, when i want to turn the wheel fast and induce oversteer for a quick u-turn or something it just plows. this could be partly due to my lack of an alignment, but without my rear bar I really lost the turn-in response.

when I had FM springs and no rear bar I didn't notice this as much, so I think bringing the FRC back down a little should solve it still without being tail happy in other situations.

that's the feedback I'm looking for, turn in at speed, under accel and not too loose in the rear. I planned on keeping a stock rear bar and keeping a spring rate the yellows can handle. I'd be interested to know if the rear bar fixes your quick turn in problem

700/400
good valving and a couple clicks of adjustment in front and rear really made a HUGE difference.
RB front bar
FM rear bar

I wish I went 100lb higher front and rear. Well, I ordered 800/500 but someone received the wrong springs and I got to compromise and get my car on the track.

I'd go with a decently mid/high front spring to keep the car off the stops. I like my 550/300 much better than the previous 400/300, and the car is actually smoother and more controlled.

i don't know how well the koni yellows could handle the 550 front, it's kinda borderline from what I hear. I wonder, based on your ratio how well a 450/250 would work?

That's what mine started doing with the clutch pack diff. Still haven't found a good way to tune the suspension around it. :(

from what I can gather on the fat cat calculator abs feedback I'm getting is that in a sense, FRC is neutral at 50%, which makes sense, bur driving conditions such as hard turn in, acceleration and other factors are hard to account for. I'm guessing this is why you guys running 700/400 and other high rates do better because you're less effected by these variables. I've come full circle to once again confuse myself.

track != street

exactly, I'm looking for that compromise. That's where the black magic comes in.

My 700/400 springs are more comfy than the very comfy Bilstein HD/MSM springs, and almost as comfy as the stock 1.6 springs w/ Bilsteins. If you rode in the track car you'd never guess the rates are that high...valving is amazing.

you're running revalved bilsteins? I may revalve my extra set of koni's so I can run higher rate springs