Suspension gurus. Spring rates for my car, w/ Konis.

Post by **thrdeye** » Tue Nov 23, 2004 12:29 am

Well,

I think it's gonna be Koni Yellows at 450 (deabting 450F/500R) all the way around with the Ground control coilover setup. This should cost me right about $950, and do everything I need them to do.

You do get all 4 perches and springs with the GC coilover setup for $399, right?

ConeJunkie · Post by **ConeJunkie** » Tue Nov 23, 2004 6:28 am

I have the Ground Control & Koni yellow set up on my car. I have 350F/450R springs and I find the ride to be a little on the harsh side and you do pick up a extra rattle or two. The Koni’s for your car are they inserts or a replacement?

Post by **thrdeye** » Tue Nov 23, 2004 7:10 am

They are inserts, gotta hack the stock struts.

MARKP · Post by **MARKP** » Tue Nov 23, 2004 8:08 am

The Ground Control kit for my car came with every bit and piece I needed to make it an easy installation (easy for grinding and welding on new perches). I would definitely suggest using their kit--top notch.

Keep in mind that comparing spring rates between different models of cars is pure speculation. There is a lot that goes in to the ride of a car other than the spring rate alone. The rates I run on my car, for example may be way too soft off for an SM Honda. You have to take into account the leverage the spring has on the wheel based on where it is located, among other things.

Williampreza · Post by **Williampreza** » Tue Nov 23, 2004 8:19 am

The spring rate you want depends for the most part on what ultimate suspension frequency you need. According to Don Alexander in "High Performance Handling Handbook", the "best" suspension frequencies for various surfaces are:

Smooth surface- 3.2 cps (cycles per second)

Moderately Bumpy Surface- 2.2 cps

Very Bumpy Surface- 1.2 cps

With that in mind, do you want me to post the formulae for getting suspension frequencies from spring rates? I didn't want to post until I knew you wanted them. (used to have it all worked out in a spreadsheet, but I deleted it when I sold the wagon

)

Post by **thrdeye** » Tue Nov 23, 2004 8:54 am

I have been looking at the supplied spring rates with the popular coilover setups out there.

Most are 7kg front/ 5kg rear, except the TEIN which is 8/6.

Autocorssers usually run either the same rate all the way around, or a little higher in the back than the front. This helps the Impreza rotate much easier, and would probably allow me to turn down the sway bar in the back, and have a more independent suspension - hence my inclination to go with 450/500.

Some people say the Konis can handle 600, some say 400, I figure I play the middle of the road, see what happens, and revalve if necessary.

I appreciate the offer for the formula, but I suck at math and I'm really not doing anything different than other people have done. Just trying to spearate opinion from fact.

I've got a couple months before I start buying.

Thanks

dfoulk · Post by **dfoulk** » Tue Nov 23, 2004 10:44 am

Just remember that when you set your car up to rotate really good in an autoX, you may be end up with a street car that will be an oversteering handfull in an emergency.

In a past chapter of my life (30 years ago), I used to do this to Saab Sonetts. Sticky tires, a couple of degrees of negative camber and a Saab 96 sedan front antiroll bar for the front. Shortened Saab 95 station wagon rear springs and rear axle, which was stronger due to thicker tubing, for the rear. Driving one of these was a blast but every time I lost control, I spun. I was lucky, only once did I have to have one pulled out of a ditch.

With ABS and modern tires you may be able to get away with it on the street but do be careful.

Dewey

Post by **thrdeye** » Tue Nov 23, 2004 11:32 am

dfoulk wrote:Just remember that when you set your car up to rotate really good in an autoX, you may be end up with a street car that will be an oversteering handfull in an emergency.

In a past chapter of my life (30 years ago), I used to do this to Saab Sonetts. Sticky tires, a couple of degrees of negative camber and a Saab 96 sedan front antiroll bar for the front. Shortened Saab 95 station wagon rear springs and rear axle, which was stronger due to thicker tubing, for the rear. Driving one of these was a blast but every time I lost control, I spun. I was lucky, only once did I have to have one pulled out of a ditch.

With ABS and modern tires you may be able to get away with it on the street but do be careful.

Dewey

Thanks Dewey.

I have thought about this, and I have decided that although I cannot control the action of others, I am a pretty safe driver overall and I really don't drive hard on public roads (ask anyone who has driven the dragon with me).

Once I get used to how the car will handle, I think I'll be okay.

TonyBolton · Post by **TonyBolton** » Tue Nov 23, 2004 2:26 pm

I ran 400's and 600's on my Integra way back when. The ride wasnt bad at all in my opinion. It was coupled with some OPM coilover kit and some revalved/shortened shaft Koni's.

The car was very oversteer prone with the huge rear swaybar, but with the LSD up front and a sensible head, it all worked well together. Your car being much heavier, I dont think 500's and 600's would be out of the question.

Williampreza · Post by **Williampreza** » Tue Nov 23, 2004 8:12 pm

thrdeye wrote:I have been looking at the supplied spring rates with the popular coilover setups out there.

Most are 7kg front/ 5kg rear, except the TEIN which is 8/6.

Autocorssers usually run either the same rate all the way around, or a little higher in the back than the front. This helps the Impreza rotate much easier, and would probably allow me to turn down the sway bar in the back, and have a more independent suspension - hence my inclination to go with 450/500.

Some people say the Konis can handle 600, some say 400, I figure I play the middle of the road, see what happens, and revalve if necessary.

I appreciate the offer for the formula, but I suck at math and I'm really not doing anything different than other people have done. Just trying to spearate opinion from fact.

I've got a couple months before I start buying.

Thanks

I don't blame you. There are a lot of great setups out there for the WRX sedan. The wagon was terrible to buy parts for. Even when I bought tires, I felt like I was reinventing the wheel.

Post by **thrdeye** » Wed Nov 24, 2004 8:46 am

Update.

Step one completed. Picked up a set of stock WRX struts for $40 shipped. Now, I don't have to hack my stock ones.

tnturbo · Post by **tnturbo** » Wed Nov 24, 2004 9:10 am

Are you talking rates for coilovers or conventional springs. On a Mustang I have personally run 1100 pound front springs and 300 pound rears without too much complaint on the street with conventional placement. On the Mustang switching to coilovers gives a different motion ratio and spring rates, for the front anyway, go down dramatically. 400-475 is the stiffest fronts I am aware of anyone running on coilover Mustangs that EVER drives on the street. WRX may, probably is totally different. Are all the springs you are looking at linear rate? are the coilovers 2.5" or 2.25"? any possible clearance problems switching to coilovers.

I'm a little bit down on Koni right now personally, but I know plenty of guys running 400lb fronts springs on Koni DAs 475s are fairly common too among the more track orienteed guys.

Post by **thrdeye** » Wed Nov 24, 2004 9:18 am

I think in the mustang, the wheel has a big mechanical advantage over your springs, right?

The stock WRX already has a coilover setup, stock.

The springs will be linear, and I believe that they are 2.25"

Post by **thrdeye** » Wed Nov 24, 2004 11:05 pm

Update.

After some searching, found that my current springs are somewhere around 180lb/in

gbwrx · Post by **gbwrx** » Fri Nov 26, 2004 5:28 pm

Man I thought those spring were just a little bit stiffer than that.

Well I too have been reading quite a bit about this on the boards also. Was thinking about getting coilovers untill I found those Koni's for so cheap. I had been noticing that most people have been running around 800/600 or 700/500 (others a little bit stiffer too). I mostly have heard people saying that the konis will go up to 400 lb springs and will have to be revelved for anything more. I personally have been thinking that I am going to keep the prodrives springs with the konis for a little while then send them out and go somewhere around 500 or 600 lb springs so that it wont be too harsh as a daily driver. Just my $0.02