Help On Deciding Spring Rates
 

I'm trying to determine what spring rates to get on my next dampers.
Atm I have 6k springs front and rear with Eibach sways. The front sways are rated at 10k and the rear at 6k. I find the ride acceptable with this set up even on crappy roads. I am guessing that the sway bar rates cannot be just added to the spring rates to get an equivalent spring rate without the sways. I am intending to put the original sways back on but they are rated so low (2.5k/2k) as to be not as significant with higher spring rates.
I know that CSG's car is running 10k/12k (:eyebulge:) and Mike and others says the ride is surprisingly compliant given those rates.

Things that come to mind.
1/ People's idea of comfortable is subjective.
2/ My car is a daily driver that I track, not the other way around.
3/ Everything's a compromise.

With no opportunity to have a ride in a car with decent dampers I am unsure on what rates to get. I was originally intending to get 8k/9k (1.4k difference at the wheels) but I wonder if 9k/10k (1.7k difference) would be acceptable. These rates keep the front/rear ratio close to 6k/6k (1.56k). The thought of 10k/12k (1.32k) just plain scares me even though I've been never in such an equipped car.

Could people tell me their experiences with their well damped highly sprung cars?

Our 10k/12k is more compliant than stock, per 3d accelerometer readings on our AIM solo DL.

Damping has more to do with ride comfort than raw spring rate.

There's gotta be SOMEONE in your area with nice dampers. Even if it's a different car, get a ride. Your mind will be blown.

We run 16k and 18k square on our S2ks.
@ImperiousRex is on 9k/11k, but has a rear aero bias. It'll still rotate at high speed :D

I think I need new glasses. I swear you have written 16k and 18k there.
I will go damper hunting at the next track day :)

No need to get new glasses. It's not worth quoting spring rates from another car...they are not directly comparable without knowing the motion ratio. Then you can look at wheel rates.

From a quick google search, the motion ratio for S2ks are around 0.7 front and 0.67 rear.

16 * 0.7^2 = 7.84
18 * 0.7^2 = 8.82

So that's not that bad at all.

What kind of tires do you run?

Very stiff rates on lower grip street tires will not make you faster and will make the car hard to drive.

- Andy

Hows 14k/16k on our WRX? Geometry is almost the same as the FRS :)

That's pretty firm. :)

- Andy

I'm always going to defer to CSG_Mike on this stuff, but since OP asked me to post my thoughts here, here's my take in layman's terms.

You need to figure out which damper you're going to get first before you should worry about the spring rate values. Every damper is different and every manufacturer is going to have a different valving based on their target application of the product.

Mike's 10/12k set up is on Tein SRC with their custom valving. My 9k/11k set up is on JRZ RS with settings for my driving style. I'm sure Andy has his own thoughts with the RCE set ups.

I will say that my JRZ's came default with 10k/11k springs and after driving for several months with that set up, I found that the car would be easier to drive with a rear that has a little more progressive oversteer bias. So with that in mind, we've found that having a stiffer spring ratio in the rear is better for high speed transitions and we can tweak with tire pressures/sway bar settings for fine tuning on specific tracks. And we softened the front rather than going stiffer in the rear just for a little more street compliance but I think the coilovers could've been set up to work either way.

Your driving style will dictate what will work best for you.

I am using Kumho 225 V710 on track. My concern is/was about running 10k/12k for daily driving.

Yeah, pardon me. CSGMike had already read a previous post of mine where I was asking about AST 5200s so I didn't think to re-post that info here.

Aaaarrrrggghhhhhh!

What did you think of those rates for street driving at sedate speeds?

You'll likely have a different set of damper settings for street driving, but once you dial it in for ~1.5 oscillations, you'll have a surprisingly smooth ride.

I wish you were local; we have a LOT of high end damper users in SoCal. It only takes one ride to be convinced that it's money well spent.

Just get really stiff 18k springs. Then, if you want to adjust to softer rates and a lower height, cut coils off..two birds in one stone and super versatile! Boom! Top secret trick bro.

I think the 9k/10k with stock sways that you're thinking of will work well. If you feel you need more roll resistance, you can think about adding your aftermarket sways back on.

I think we were running 9k springs on our RS1s when we were testing them for JRZ....they were VERY smooth. AST 5200 probably won't be quite as smooth, but they are quality dampers.

- Andy

How about STi Pinks? Are they any good?

You would never guess that the spring rates were that high - it almost feels like stock. You can feel a little stiffness on impact with speed bumps and what not but the car settles very quickly. On the freeway it's very comfortable.