Rep Power: 0

I'm getting ready to get a full coilover set-up soon and I thought I'd see if anyone could help me choose spring rates for my taste (don't mind being a little stiff), type of driving (will be auto-xing and on road course), and the other type of modifications I'll be using with them (strut bars high and low, bigger anti-roll bars.)

The spring rates should also match the car's weight distribution, that I understand (I believe ours is 59/41?)

Anyone wanna ?

 
Rep Power: 412

depends on how stiff you want to go. i think a consertative distribution of spring rates will be good. KW's 350/500 is good, but I would go a little higher. Maybe 400/525 or 425/525 That is REALLY stiff. JIC's are 450/506. If you wanted something like that then do 450/550 or 450/575, but that is getting really really stiff. you also would want to look into camber and caster plates. a nice combo for sway bars would be the progress bars. Rear strut bar i suggest cusco and front i suggest neuspeed. the X brace isn't legal in STS or i would have suggested that.

Once ZzyZx gets to this thread you will have plenty of numbers. He is better at it than I am.

 
Rep Power: 424

You're probably going to have to make up some numbers for yourself. It depends how stiff you want the car to handle. I personally don't mind it being a little loose (so it slides a little), so I'd probably pick something lower than someone who wanted it super stiff.
I would't base too much off RSX rates.... a K20 weighs a bit more than a D17. If KW is using 350/500 in an EM2 setup and you wanted stiffer (more neutral), I'd probably just push up the fronts a hair, 375 ish, then crank up the rears, maybe 550-575. The firmer the rear is, the more neutral the car should be, but keep in mind that the stiffer you make it, the more prone to oversteer it will be. Don't over do it. Also don't forget that if you can dial in damper stiffness (and you're getting custom valving done), you should be able to dial quite a bit of the spring out if you can set the damper super firm.

 
Rep Power: 0

what do u mean dial quite a bit of the spring out if he set it super firm>?

 
Rep Power: 412

Change the dampening on the shock from soft to hard. you use a little "dial" at the top of the shock body.

 
Rep Power: 0

thanks again!

 
Rep Power: 380

How much effort are you willing to put in to finding out what would be the "Perfect" spring rate for you????? because it can be done. it just takes some measurments and a little math, and you can calculate what would be the optimum spring rate for you.

What you need to find out is the wheel rate and the suspension Frequency. WHEEL RATE is the actual rate of a spring acting at the tire contact patch. This value is measured in lbs/inch, just as the spring rate is. With our suspensions it will always be less then the rate of the spring itself. Once you calculate the wheel rate then you can calculate the suspension Frequency which is the number of oscillations or "cycles" of the suspension over a fixed time period when a load is applied to the vehicle (Like hitting a bump). Suspension frequencys are important for racing because in a racing application , the primary job of the springs is to keep the tire contact patch loaded and on the racing surface over bumps and ruts. rather then adjusting the roll couple (handling ballance). so if you calculate the suspension frequency you can figure out what is the stiffest spring you can run for the road surfaces you drive/race on. the smoother the surface, the higher the spring rate, the rougher the surface the softer the spring rates. this dosnt mean that the springs would no longer be used to adjust the roll couple, because the amout of spring rate change needed to change the suspension frequency is larger then the amout of spring rate change that would be required to adjust the roll Couple (2% is enough of a change to notice). So you'd want to find the range of suspension frequencys that is adequate for the roads you drive on, and then find the roll couple that would give you the handling ballance that you want (that fits in that Suspension Frequency range).

So before I write a book, are you interested in finding this stuff out? I know I am, but I lack the equipment and time to do it at my appartment.

 
Rep Power: 412

see i told you...all you have to do is get him started and he is like a big book of suspension information!!

 
Rep Power: 424

basically what I mean is if you can set the damper stiff enough... it will bear a good portion of the load put on it. The spring does less work because you've got the damper set stiff enough it won't move a lot... so its like locking the suspension in one place, and the spring won't compress a whole lot.

 
Rep Power: 0

What kind of equipment and how much time? Sorry for the late reply... I've been short on time myself. Thanks for all the priceless info.

 
Rep Power: 0

Oh yeah, and why isn't the X-brace legal in STS?

 
Rep Power: 412

fro what zzyzx says, it doesn't attach to the control arm bolts and thus isn't legal.

 
Rep Power: 380

yup, the X-brace isnt legal for STS,

Strut bars are permitted with all types of suspension. Strut bars may be mounted only transversely across the car from upper right to upper left suspension mounting point and from lower right to lower left suspension mounting point. No other configuration is permitted. Additional holes may be drilled for mounting bolts. Only bolt-on attachment is permitted. because the X brace is an X and its not legal for STS same thing for the Tanabe brace..

As far as the suspension, I found a nifty java scripted wheel rate calculator its made for RC cars, but I think it will work for us. all we need is a couple of measurments off the control arms of the front and rear suspension as well as the angle that the shock/spring attach to the control arms.

once we do that we can calculate the suspension Frequency of the car by.... using the formulas found here

after that, we can use different spring rates to get the suspension frequency you want..
for a smooth surface the suspension frequecy should be around 3.2 cycles per second, for a moderatly bumpy surface it should be close to 2.2 cycles per second and for a rough surface it should be around 1.2 cycles per second. there should be about a 10% difference in frequencys front to rear with the higher frequency on the drivewheels.

 
Rep Power: 0

wow i am soooo confused, haha. but damn...that means if i install my x-brace...then i can't autocross with you zzyzx...blah!!

 
Rep Power: 380

Dont worry, I wont protest. untill your faster then me that is.
Regionally you wont have a problem nationally youd get protested in a second