twin - suspension inputs - springs and bars - suspension gurus chimein please

[jdbubb@ix.netcom.com (Dan Bubb)]

Allyn wrote:
> 
> ok, so say you had a twin engine scirocco...
> i'm looking for some input on springs/sway bars for the twin
> current intentions:
> - koni adjustables (front type) all around
> - ground control coilover kit
> - using stock type sway bars (i.e. 16v / 8v front type)
> - using stock a-arms, front geometry, rack, etc
> - intend for setup to be semi-streetable (but stiff)
> - before reading the following questions, realize this is not the typical
> awd car, as it will have a 50/50 weight distro.
> 
> i'm looking for decent spring rates and sway bar inputs
> spring rates: ground control guys were suggesting ~400 lbs/in, which makes
> sense, but they were also suggesting #50 less (i.e. 350 lbs/in) in the rear.
> honestly i think the guy was going with the typical front drive mentality
> and didnt fully grasp that i will be putting down an additional 200+ hp at
> the rear with more-than-typical rear weight. what do you guys think? will
> the 400/350 f/r be sufficient? or should it really be something like 400/400
> (or even 350/400 f/r) instead? another consideration is that i'm shooting
> for ~#2200 total weight. possibly less. this may mean that the 400 lb
> springs may be excessive for the given weight.

Spring rates can be pretty much anything you want depending on your
intended primary function. But if you intend the car to have reasonable
ride quality then the front to rear ride frequency (if you removed the
shocks and bounced the car up and down just on the springs) should be
set up so the rear has a higher frequency (there's a formula which I
don't have at hand). If your car is 50/50 weight distribution then for a
higher rear frequency the rear springs would need to be stiffer. I'd
think 350/400 f/r or something in proportion. But this is just based on
ride not handling although it wouldn't preclude good handling.

> 
> sway bars: whats better for an awd car? matched bars? stiffer in rear just
> like fwd? my current thought is either 16v bars front and rear or 16v rear
> and 8v front. keep in mind i dont need outrageously stiff sway bars as i
> will be running pretty high spring rates to begin with.

As far as sway bars they can be anything and IMO are the easiest chassis
balancing device. They should be determined after you've set spring
rates, roll center heights and any other suspension variables that
affect front/rear balance.

Dan
>