Lizard928

I have run 1000/500 on the internally adjustable Koni's.
I then went to 1000/600.

I found that the low speed dampening needed to be stiffer, but the higher speed was not too bad.
That said though, the high speed only really took effect at around 140kmph or so. I5 is a horrible drive with that suspension.

And there is no 1 right suspension, everyone drives differently.

I found the 1000/600 ok on the street, and pretty good on the track. I had very little roll with this setup, but that said, I am building a track suspension right now for my car and I will be running with much higher rates in that car.

if you are driving on the street then I would recommend 500/350 with Koni's. I like Carl's Koni coolers, but I dont like the rest of the kit as IMO it is over priced. I did this setup recently, and got the shocks for under $600, and the rest of the needed hardware for around $100. Compared to Carl's $1500 price tag.
This setup was good for the street, but does have some roll, and is ok at the track with street tires. But the same shocks with much higher spring rates will be faster around the track.

And yes suspension work is the black art, what works for 1 will not work for the other, and then there are drivers that can get into any car, with any suspension and make it fast.

hacker-pschorr

I'm starting to think Mark Anderson just might be The Stig

tv

Well this is what I mean Mike S says 2000 and Lizard says 500



There is 1 ideal suspension for the STREET and it has nothing to do with how you drive the car. As long as you agree that zero dive, zero body roll, and non-jarring absorption of road irregularities for a street car is the ideal then achieving that is ALL up to the suspension and has nothing to do with how you drive.

Zero roll is zero roll whether you take the on-ramp at 35 mph or 85 mph. Zero dive is zero dive whether you slam the brakes at 20 or 100.

and springs that are 1500 lbs apart will result in a difference.

FBIII

I don't think you want zero roll or zero dive. A small amount of weight transfer is a good thing.

Lizard928

500# springs will dive, and roll.

I would not put most drivers into a car that had zero roll/dive.

you also forget that the new cars have electronic shocks.

hacker-pschorr

That's where the new Koni FSD shocks would come in if made for the 928.

I've talked to a few people that have them and they seam to live up to the hype.

There isn't any reason why they couldn't be produced or our cars, just takes one vedor to make a phone call........

tv

So lets agree that the higher spring rates will achieve the less roll/dive which is what we want. I am actually aware of many different types of suspensions from air cushions to magnetics to F1 hydraulics in the 80's. But we have to use what is available to us.








1)The widest, stickiest tires possible for avoiding slippage and loss of traction.

2)The least roll/dive attainable for driver feel/position/comfort and to feel g's of braking/cornering (like a rollercoaster) and to keep weight of vehicle from shifting too much and making tires lose their traction.

3) The correct damping of the right shocks to absorb holes/bumps w/o jarring driver or making car hop.


The rubber bushings and the comfort/padding of the great seats doing their part. You are just in a better position to control the car and enjoy the ride if the car stays level, then you can use the pedals to affect where you go.

















Some highlights from that article;

Coil springs can also be upgraded to shorter, stiffer versions that reduce the lateral weight transfer and sway

Dampers that are properly selected and valved, actually dampen spring oscillations and keep the tires in contact with the pavement. They also manage weight transfer during cornering and braking. Dampers control both the amount of weight transfer and the rate at which this happens. Basically, this means that all weight transfer transients, such as when entering and leaving a corner or changing direction, are controlled by the damper settings. The rate of weight transfer caused by braking and acceleration is also affected by damper valving



we feel that the vehicles’ springs should carry the majority of the desired roll stiffness, not the swaybars. These should be used as tuning tools, not primary roll stiffness components.

Mike Simard

Speaking of Astons, their recent DBsomething racer uses no rear swaybar.

I also use no rear swaybar in mine. That's because I don't want rear grip compromised at awkward times. There are times when you're on an uneven surface and having the inside rear wheel be light can cause your car to lose control. That's not such a problem in the front. Too much rear swaybar is a dangerous thing!

tv

do you mean FSD? http://www.koni.com/190.html

Sounds good and reasonably priced, that is a good idea. Wonder if we can get them?




Edit: quote from a 3 series bmw owner on another board;

Always a fan of cool engineering, I was intrigued. These sounded awesome. I did some research, and decided I'd buy a set and install them in the spring, once I had switched back to my summer tires. But sometime in January, I decided "Why wait?" and bought a set from Tirerack.

It was a bit of a risk, because I could only find one review (the one from Roundel). But I've had them on the car now for about 1000 miles, and all I can say is: they're amazing.

I was initially worried that, despite the promises, they would make the car ride like an old Buick: soft, mushy and floaty. That is definitely not the case. When I drove away from the shop that did the install, my immediate impression was that they were significantly stiffer than the stock shocks. The car feels tighter, lower to the ground (even though it isn't), and just more stable and controlled in general. The difference is especially noticeable when cornering and changing lanes - the FSDs allow a lot less initial body roll than the stock sport shocks.

But the improvements in handling are absolutely nothing compared to how these things handle bumps. For most irregularities where the pavement is unbroken (dips, rises, gentle lumps, etc.) the car still feels stiff. But anything more abrupt (usually anything that breaks the pavement - potholes, expansion joints, sudden surface elevation changes) just gets soaked up. I'd say it takes anywhere from 50% to 80% of the edge off.

It's really almost surreal, because at no point does the suspension feel soft. Yet somehow, the same bumps that used to feel and sound like driving over exploding grenades just turn into muffled thumps.

hacker-pschorr

Oh yea, FSD......

FBIII

I ended up with bars that were way too big on my DB4 initially. Inch and a qtr in the front and 3/4 in the rear. The car just slid off the track. I couldn't weight the outside wheels suspension. I was using the setup Herb Adams recommended for the f cars. The flaw in my thinking was tire size and track. The f cars could run a much larger tire and the cars track was also considerably greater.

ptuomov

I read about those shocks a little bit and they seem to be exactly what the doctor ordered for me. I'm in if someone gets this done.

I sent Koni a message thru their web page, but I am not holding my breath for an answer. Perhaps some of our vendors who carry Koni products would get some traction.

Okv

I have 500/350 with custom Bilstein BM5 adjustables.

When driving the car out from the garage after mounting it, I immiediately got the impression that this is too soft and will not work as I had predicted and wanted.
This is confirmed when driving the car.
Nice, but not the solid feel of a well tuned sports car suspension, and cranking up the shock settings really does not help since it then gets very harsh and hard especially over edges and similar sharp irregularities.

The suspension frequency is too low up front, meaning, the front springs should be stiffer.
The rear end is rather stiff in relation to the front.

When setting up a suspension, one should start with deciding the desired suspension frequency, and then select spring rates according to that.
Then you need to know the weight on each end of the car and the spring ratios, and the springs can be calculated.
No voodoo, only simple and pure engineering.

An undriveable POS would have a frequency less than 1 Hz, a racing car around 2 to 3 Hz, and a nice sports car set-up around 1.5 - 1.8 Hz.
The front should be slower, i.e. lower frequency, than the rear, to avoid undesired pitching motions.
This is what the experts say.

If I had been more careful doing the calculations I would have ended up with a stiffer front spring, or softer rear spring.
Simple measurements on the car confirms this error, front is 1.35 Hz and rear 1.68 Hz.
(Numbers are well within expected tolerances of the measurement).




So, I here by present some approximate numbers of spring rates and corresponding frequencies, for the S4/GT/GTS:

Front spring (ibs) Rear spring (ibs) fs front (Hz) fs rear (Hz)
257....................186....................0.91............1.16
500....................350....................1.27............1.59
600....................400....................1.39............1.70
850....................450....................1.65............1.80
1000..................500....................1.79............1.90
2000..................750....................2.54............2.33



If the car is lighter, the spring rates must be adjusted accordingly - lower weight -> softer spring for same response.

From the table, we see that the stock springs are very soft in rates compared to what some prefer, and the car response is around 1 Hz, for a not too soft but still comfortable GT-ride.
On the other end of the scale, as you approach 2.5 Hz, this is a very stiff suspension which I suspect would be very strange to drive on the street.

In between, there is a huge range where most of us will find our preferred settings for a given day and trip.
The 1.27 Hz front (500 springs) feels much more stable and planted than stock, but will still give some noticeable body motion in terms of roll and pitch.
I suspect my preferred setting is some above that, may be in the 1.5 - 1.8 range.

The stock springs are still kind of driveable, perhaps because the roll stiffness is still good and the center of gravity is reasonably low.

I suspect shocks should be adjusted according to springs, so that when the springs are selected, the shock settings are also already decided within some range, because the repsonse should be reasonably damped (Like does not bounce several time up and down by itself), but not too much overdamped, as it then will induce slow-motion offsets because it does not return to ride height fast enough.

IcemanG17

while I am far from an engineer......I have driven many different 928's on track and the different suspension setups make a HUGE difference in feel....I've driven everything from worn out S4's to full race 928's (but not the super stiff springs like Mike, though I would love to try it)

http://www.youtube.com/watch?feature...Fcobrastrike27

At about 2:00 the above video shows a great angle of the 928 estate with bilsteins and cut eibachs (just about 600f 400R) set to a pretty low ride height on track going over a bunch of bumps....while it is STIFF, it is not harsh...& roll seems pretty well controlled running bone stock sway bars....

928 at last

So, quick question then, as many of us are going to / are running them, what are the specs on the Eibach's Mark had on sale?
I'm new to the science and engineering here too.