rear spring rates to limit squat

[nazar]

Ok i have an lt1 making 330whp with a q45 rear end and 6 speed and 275/45/17 tires

 

I am getting flares for the rear and have cut out about 2" of the rear fender height.

 

Right now i have about 2" gap between tire and fender and even though the car has some blue springs on it(i think zcarparts springs) it still squats way way way too much under acceleration and is shreading my tires, and under turning as well

 

How stiff of a rate should i go in the back to limit my squat to about 1.5", not much more.

 

I am not used to the z world because my eclipse has a tein coilover setup on it that came with 500lb springs up front and 340lb in the rear(FWD)

 

So when you guys talk about max springs being 250lb, it makes me laugh, cause i guess that sounds way way way too soft for me

 

Why do you guys use soft springs like this?

 

Anyways, I was thinking a 300lb but am worried that it will still be too soft

 

Im not running a rear sway bar. I will be using illuminas for shocks, or konis

 

I would like limited squat, and i have driven stiff cars all my life so im not too worried about loosing the cadillac ride, its a fun car, not a daily driver, i dont care how stiff it is as long as its not stupid stiff

 

The front surprisingly is much stiffer then my rear, not sure why. I can practically push down hard enough to hit the tire to the fender, which is about 3"

 

THanks guys

[Guest iskone]

Well, I can't really give you themost info but I can tell you that 300lb in a Z is very stiff and I like a stiff ride too. I wouldn't worry about it being to soft at all as a matter of fact I'd try 275lbs first.

 

Someone else could chime in.

 

Isk

[260DET]

You have a Q45 rear end in a S30? Don't know what a Q45 is but guessing it has the usual Nissan multilink setup.

 

The problem could well be caused by soft springs but it may also be related to how the multilink sub-assembly was installed. Tilting it forward, down at the front, will increase squat by effectively altering the suspension geometry.

[JMortensen]

Different suspension systems have different leverage ratios, plus an Eclipse is probably 800 lbs heavier than a 240Z. Some suspension setups need MUCH higher spring rates to get the same effect at the wheel (wheel rate). I don't know what the Eclipse is like, so I can't say that this is definitely the difference, but I'd bet that 500 lb springs on that car are like 250's on a Z. http://e46m3performance.com/tech/wheel_rate/index.htm

 

On a Z, once you start getting over about 250 you're getting into race shock (read really uncomfortable ride) territory. And in order to make springs and shocks that are that stiff work in a Z you'll need to beef up the chassis, otherwise the body becomes the spring and then the handling really goes to crap.

[Dragonfly]

Different suspension systems have different leverage ratios' date=' plus an Eclipse is probably 800 lbs heavier than a 240Z. Some suspension setups need MUCH higher spring rates to get the same effect at the wheel (wheel rate). I don't know what the Eclipse is like, so I can't say that this is definitely the difference, but I'd bet that 500 lb springs on that car are like 250's on a Z. [url']http://e46m3performance.com/tech/wheel_rate/index.htm[/url]

 

On a Z, once you start getting over about 250 you're getting into race shock (read really uncomfortable ride) territory. And in order to make springs and shocks that are that stiff work in a Z you'll need to beef up the chassis, otherwise the body becomes the spring and then the handling really goes to crap.

 

I agree with Jon on this once you get over about 250lb springs they will destroy your strut inserts. I will also tell you that I am running 300lb springs on the back of my Z and 250lb springs on the front. I was also running with about a 1" gap between my tire and fender lip and the only time I was ever able to get the tire to hit the fender was when I had a passenger and hit a bump at a high rate of speed.

 

Dragonfly

[Guest zfan]

I had the same problem and found the fix. I converted to the ground control coilovers with 8" 250 lb. springs and new struts. I used to have the Arizona Z springs in the back with Tokico blue struts and under a hard launch the rear would squat and rip into the tires.

 

It doesn't happen anymore. I am not running the fastest Z around, high 10 second quarters with 1.50 60 ft's and no squat and the car is faster now that it doesn't squat as much. I guess it is less wasted motion.

 

Mike

[Dan Baldwin]

Shocks will go a long way to limiting squat. Too much spring rate (and commensurately increased damping) will not hook up as well. The S30 rear geometry is not as squat-prone as semi-trailing arm IRS setups are. Even with 330hp, I'd say 200-250 lb/in springs with good shocks and you won't have too much squat.