Completely depends on corner weights and if you are trying to lean the car towards more understeer or more oversteer.

On my first set of coils(soon to be installed). I have opted for 10KF/12K rear. This will produce a front ride frequency of 2.0 and a rear of 2.3
2.0/2.3 = ~.86 which is on the understeer side, and is almost identical to the OEM ride frequencies. It's also almost the exact ride frequencies of the swift spec-R.

The mfgr's tune to this frequency on purpose, understeer is safe. Almost every single OEM vehicle is going to be close to this ride frequency. I figure I will stay close to OEM, but at a stiffer spring/wheel rate, as to not make too drastic of a change. The car will behave similar to it does now, but won't roll over as bad.

Now if you wanted to dial in some oversteer which is more typical of a race car setup(looser). You would bring the front rate much higher. Something like 14k/10K on oem spring location would produce

2.3/2.1 = 1.12. Which would be mild oversteer and is pretty well balanced and is probably what I will do next for a stepping stone.

The big no-no is to do something like 2.1/2.0 = ~1 as was explained to me by an engineer(this is not my math I just know the equations).

As he described it to me, anything in the range 0.9-1.1 is flirting with some real problems and can get you into trouble. You always want to aim outside of those numbers either towards understeer or towards oversteer.

Well, in my case I've switched to true-type rears, so I can't directly compare the ratios from the stock spring setup anyways. The rule of thumb for avoiding near-1.0 (I assume for harmonic reasons between front/rear bounce) makes sense, but I'll have to figure out how to do the freq calculations for my setup first.

My current setup is definitely oriented in the oversteer direction (not that I know the math, I just know that every single time I get close to being in trouble, it's from oversteer not understeer, even in a faster sweeping corner :p), and I'm pretty comfy with that.

I think you need to go back to that engineer and have him run you through it again...you didn't grasp it the first time.

2.0f/2.3r is going to be loose, 2.3f/2.1 is pretty nuetral and 2.1/2.0 is a little soft and probably still on the nuetrul side (tending towards oversteer)....

Fwiw, my race car sits in the 2.4f/2.25 and tends towards slightly loose on corner exit and that is with no rear bar.

Which one of you true type rear coils guys needs SPL toe arms?!?!?!

Agreed im running stock nismo bar in the rear

have to find out first. all i know right now im 57/43 weight ratio so the rear is way happy!

finally someone talking about frequency! i have no idea what youre talking about but was trying to tell someone and couldnt say it right so he had no idea what i was talking about. if you could PM we wont thread jack, i have a ??

1000lbs springs are still softer then bump stops :D

before any spring rates get changed around, i think that rear Hotchkis needs to go and be tested with stock. then further tuning from there.

with both the weight balance of the 370 NOT being 50/50,. and the high amount of both front grip potential with sqaure tire setup, decently high levels of unsprung weight, and the wishbone suspension, i think the front really needs a good amount of rate. depending what rear rate you need depends on spring location (stock or true coilover), sway bar selection in back (large, stock, or none), power level, and LSD.


I run G37S coupe rear bar

Ok one more thing: I know the exact brand and type of coils on my RS1's: they're HyperCoils, and their model number system is pretty simple (they go by "free coil length", basically a coil count, the I.D., and the spring rate). So the ones I have now are 8A0500 rear (8 coil, 2.25 ID, 500 lbs/in), and 6A0650 front (6 coil, 2.25 ID, 650 lbs/in). You can see their catalog page here: http://www.hypercoils.com/skin/front...Catalog_12.jpg , but basically I can pick any reasonable rate and coil count I'd want.... do I need to change the length when I change the rate, or keep the same length as the ones I have and just change rates?

Make it easy on yourself, just get a pair of springs in 50lb increments from 600-1500lb....

Best answer!

Syno, you actually setup perfectly for doing doughnuts in the snow.

350 completely and respectfully disagree. Disagree since the freq calcs include corner weights, The guy I am talking to is Gordon Benson from Koni that engineered the 2812 long body. I know Koni these days isn't the "cool kids" choice of dampers, but math is math. If you want email him at Gordon.benson@itt.com. Guy is awesome and will even get into the calculus of it.

Every post market "spring kit" out there tunes to something around .80-.85
because they can sell that product and not kill someone. Or at least not be sued for creating an "unsafe ride rate" as per the DOT.

that being said, I don't drive your car that you know intimately. I see what you are saying, because you know your car's frame, your sway bars, your tires, what you like, etc. better than I do, and are a much more experienced driver. But as for a baseline tuning point, and to understand how a suspension works(regardless of the car) the Front ride Freq/ rear ride Freq, tells you how the car is setup. <1 induced understeer. > 1 induced oversteer. That's not my opinion that's just physics. Doesn't tell you how to drive it fast, doesn't make you push the throttle when you know you maybe shouldn't, it's just a reference point.

:drama:

:p I'm sure I'll end up closer to that than I want to be, eventually. But the nature of my earlier question, if it wasn't clear, is more like: if I change a spring rate dramatically and want to maintain approximately the same suspension stroke and ride height, do I need to buy shorter springs when I buy stronger springs, because they won't be as compressed when the car is static?

Who made the sway bar? I wonder if they would sell some.:tup:

What end links do you use with this front bar?

Do you guys run a rear sway?