dannysauter

I have a 1991 camaro z28 with a bunch of suspension mods and I want a stiffer suspension setup than the eibach pro kit. I had that on but the rear was way soft. I just went up to a 160 linear rear spring than to a 190 and they were both still a little soft for my taste as i push my car pretty hard. I now have 275lb rear springs. I still have the 714lb front. I was wondering what front spring i should use to compliment my stiff rear springs. I do a lot of road racing and I have no problems with a very stiff car but it is also my daily driver. Heres my suspension setup so far Spohn torque arm TDS wonderbar 36mm front swaybar 24mm rear Koni Yellows LCA Relocation Tubular panhard rod double Rod Ended lower control arms Urethane everywhere The springs are now 714in/lb in the front and 275 in/lb in the rear What are your recommendations for spring rate in the front that compliments the rear. Also is there a ratio or rule of thumb for springrate front to back in order to balance understeer and oversteer?

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mike_c

I have Global West competition springs on the front and rear of my car. The fronts are 800 lbs/in. I can't remember what the exact rate for the rears are though... I have Koni yellow's on my car too and the combination is impressive. The ride's a bit rough on anything but a glass-smooth road, but I daily drive my car too and don't regret going with these springs at all.

Lonnie P

Not sure with such a stiff rear spring.... probably at least 1000-1100# up front.

I run 800's & 150's & could get oversteer with 36/24 bars on it. Had to go with a Strano 22 hollow on the rear to balance it out on street tires.

Your car must be scary now with your current setup.

dannysauter

If anyone else has any stiff combos let me know. I was running 714lb fronts and 190 rears with the 36 24 swaybars and it was still a little soft for me. I like my car as solid and predictible as i can with little body roll and i felt like I was still getting a lot in the back. Most of the time when i'm driving I will have at least a passenger but often I have people in the back too when i'm out in the country hitting up the mountain roads.

rayar

1000lb front, 425 rear(With a 3 link rear suspension). Small bars front and rear. Chances are it may be a little scary at higher roadrace speeds but works well on my autocross only car. Have never spun it out, but it tends to be a touch tail happy under corner entry braking. Overall it is still a bit pushy for my taste so I am thinking about trying 500lb rears. Not sure how much of this will help on a daily driver/track day car but I feel it works well on my car.

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91_5.7_TPI

That's what I was thinking. I've not seen rear rates without a relocated PHB and ~1000lbs range fronts. But, alot of it depends on the driver's taste Have you driven the car with the 275 rear springs? With 714s in the front, I wouldn't go stiffer than a 150 or 200 rear (probably closer to 150). Have you adjusted your rear shocks before putting in stiffer and stiffer springs?

Vetruck

Spring rate choices depend on the car weights, the track conditions, the shock valving choices, roll centers (ride heights and any futher added adjustment provisions welded in availiable to you for tuning), tire choices (lateral friction and resulting body roll in degrees), suspension geometry provisions (amount of geometry change in travel....etc

Spring rates are all unique for each cars modifications. It takes lots of testing to get this correct...lots of testing is lots of money. you now get it feeling good and then you change one thing like tire brand choice and you are now searching again for balance...or it could be as simple as summer weather as opposed to winter colder months and cooler track conditions that can change things.

A car is not perfect for every corner. A car needs to be set up to run a certain track best for the type of corners it will see most and will lag on the fewer corners it is not set ideal for. An example of this is California Speedway (for a local example close to me) where NASA and CMC run on the 2.8 mile road course which consists of the 1 and 2 corner high speed aprox 130 mph bank (with compression bank forced downloading the chassis so stiff springs are required to really steady the car) and then 15 other non banked various cambered infeild corners verying between about 20 mph and 80 mph. High spring rates will low roll rate on the chassis will skip a car through the low sppeed flat corners if too stiff loosing mechanical grip, however, lower spring rates will ground out the high speed bank section. most cars relax the high spedd section and focus on the harder and more timely infeild section to make up time lost on the high bank to those setting for high speed stability.

To ask the question "what spring rates" is basically an unanswerable question. Its all trial and error for the individual track and condition you plan to run. Event he pros have trouble on any given weekend even with all the history of charts and data acquistion they have availiable to them.

Dean

I H8 WWD

^ Yes sir.

As more of us get into auto-x, road racing and drifting I believe soon we will be able to get a nice starting point for a stiff track/street ride.....not comfortable, in which lowering kits are for (to me at least).

P.S. I am starting with 1000# front and 250# rear. My car will be lowered on RaceCraft Drop Spindles and a shorter rear spring. Also will use a weight jack system by GroundControl

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1988-305-tbi

i'm running 1100/200 springs with spohn 1 5/16" 1" swaybars rear roll center is1/2" higher on the chasis side unless your running no rear swaybar i would say you need atleast 1,200-1,500, not very streetable. i feel i have pushed the limits with my setup, any stiffer and the car can't handle road imperfections

i had the prokit, it's too soft in the front and too stiff in the rear, i couldn't imagine making the rear stiffer when the extra weight is in the front

from the factory the spring rates in the irocs were setup at a 5 to 1 ratio favoring the front...550/107, i would say that the 5 to 1 ration is a good starting point for a v-8 car i plan on getting the racecraft drop spindles as well,

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THE MODS
Suspension: 18X9.5" hyper black c6 wheels with 265/40/18, 275/40/18 michelin PS2, AGR 12.7 to 1 steering box .225 valve, J&M strut mounts KONI Yellow sport/ Ground Control Weight Jacks#1,000/200, double adjustable lower control arms+ UMI LCA relocation brackets, UMI Panhard relocation "chassis side" with single adjustable UMI panhard, JEGS Panhard relocation "axle side". UMI SFC's. UMI tunnel mounted torque arm, 36/ 23 mm swaybars, Iroc wonderbar, Edelbrock 3 pt STB, Moog front end steering componets, Spohn bumpsteer kit.
Intake: Ultimate T.B. + spacer, 14 X 3" open element 1.6 Comp Cams Roller rockers
Exhaust: 1 5/8" Edelbrock shorty headers through 3" Flowmaster, carsound 3" converter.