[Cloud9...68]

I've been doing some reading to educate myself on the subject of suspension set-up, and yes, it sounds like Firefish has gone about things correctly. It's good to hear that in the real world, using firm springs, in conjunction with appropriately-chosen shock firmness, creates a more tolerable ride than on a car with the inverse set-up.

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[flash]

absolutely - it's all about choosing the right combination of components, and then tuning them correctly - i have springs that are twice that of stock, but the ride is not compromised at all - i could easily go stiffer, but as this is a street car, i don't need to - besides, if i went much stiffer, i would need bigger sway bars than i already have - that is really one of the limiting factors in choosing springs - in having my bars made, i was able to go with a softer spring, making the ride quality quite compliant without adding body roll

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[steve g]

I appreciate what's being discussed here since I'm in the same situation.



Since I want to keep my stock torsion bars, what is the method or formula for determining the spring rate of the coilover spring.



I'm installing Moton Clubsports which, I am told, can take 700 F and 900 R or something close to that.

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[flash]

the stock torsions are 175#



the effective rate of the coils added is 56%



so, take whatever spring you want, multiply by .56, and then add 175 to get the new wheel rate



realize that once you get past a certain point, you want to shift that balance front to rear



stock is 160 front and 175 rear - once you get past about 1.5 times that, you need to start shifting things - by the time you get to double stock rates, you need to be about equal in rate all around - when you get past that, you start shifting things more, with the front now being stiffer than the rear



then you get to start playing with sway bars - to run the 400/600 setup (no torsions) i had to have a 31.75 front and 22.25 rear made - the M030 bars were not nearly enough



with springs like what you spec, i would guess your front sway bar should be about 34mm, and your rear should be about 24

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[Cloud9...68]

So the sway bars need to get considerably beefier as the spring rates get into the mid-to-high hundred's; who make bars of this size for the 968? Thanks.

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[flash]

yup - unfortunately nobody makes bigger ones, which is why everybody runs the M030 or Cup stuff



i have the only set i know of in my sizes, and i had them made - nobody i know of makes larger bars - you would have to have them made, just as i did



my bars will work in a spring rate range of 300 to about 500 front and wheel rate of 275 to about 450 rear

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[Cloud9...68]

A sway bar doesn't look like that complicated a piece of hardware. Couldn't a competent machine shop fabricate what you need, provided you can find the correct raw material?

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[flash]

there are a few ways to make them, and the answer is "yes" - it was not that complicated to make mine - i thought about making more, but there was no demand - the key is being able to do the torsional and materials math to get the right spring rate on the bar

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[firefish]

There is the Tarett, although I don't know the data, and the rather new sway from Racers Edge (only front afaik) but I don't have any data on that one either. Of the two, I prefer the Tarett design as it is easier to adjust and we don't have the clearance issues on our cars that would motivate going blade style.



Maybe Smart Racing, they make super beefy sways for the 911s and perhaps they'd be willing to produce for our cars too, provided that the interest is big enough.



One nice thing about the Tarett is that is very light compared to the stock unit as it is hollow. And the service from Ira at Tarett is great.



I'm not agreeing completely with flash about having to go for mega thick sways if you go high in the spring rates. It all depends on what you want to achieve. High spring rates by themselves mitigate body roll and thus weight transfer and I use my sways primarily to work with oversteer/understeer (together with shock settings) in order to get what I want as I don't enjoy playing with springs as that messes up my corner weights and front alignment.



But I not very scientific about this - if I find the rear too loose I just back down a tad on the shocks or set the sway to a softer setting. I don't normally toy with the front although I would go stiffer on the sway if I had stiffer tyres, the Toyo R888 (r-spec compound) are a little to weak in the shoulders.

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[flash]

that is what most people do, usually due to lack of other choices



if you think about for a minute though, while the stiffer outside spring may mitigate roll by resisting compression, the inside spring is actually fighting you more for the same reason



i was very disappointed in the M030 sway bars, as they were unable to keep up with my springs, and as soon as i swapped them out for mine, the car became a lot more predictable and cornered flatter



do set it up right, you really need to measure the loads on each corner in a corner, and then add what is needed to balance that back out



it's tricky and complicated stuff, and most people end up just doing it by trial and error

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[craigawoodman]

Guys,



Paragon Parts have 30mm fronts (M030), Weltmeister 28mm fronts and 22mm rears.



I am running the Weltmeister swaybars (which were apparently a real pig to fit at the front) which have made a massive amount of difference to how flat the car corners.



There is another design (more complex, but easier to adjust) - but I have had no need to play with mine since installing them.



The whole car had to be re-setup once installed as it will not sit right and will pre-load the swaybars.



I am running fairly light springs (from the invoice - 350 and 275's) but I have retained the torsion tubes/bars in the rear.

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[Cloud9...68]

I have a very simple question - Proposing one set of boundary conditions, which I think are what most people who seriously track their car would desire:



1. We are dealing with exactly one type of car (a Porsche 968 with a six-speed manual); no 944/968 hybrids

2. Keep the torsion bars (for the sake of simplicity)

3. R compound tires, section width in the 255-275 range.

4. Car weight in the 2800-2900 lb range (lightened a bit, but not a fully gutted race car)

5. Normally aspirated engine, with at most a few minor mods, delivering no more than 250 hp

6. Brakes can be upgraded a bit, but no mega-dollar aftermarket kits

7. All available bracing in place (shock tower and lower front suspension brace, and some kind of a chassis brace/roll/harness bar), but not a full race roll cage.

8. Leave the car in a condition where it is still drivable on the street (i.e. just short of a full-race set-up), but with the primary intent to be as capable a track car as it can possibly be



The over-riding goal is simply to have the car described above get around a corner on a race track as quickly as possible. Period.



Why do there seem to be an endless set of combinations of spring rates, sway bar diameters, shock damping rates, alignment set-up etc., to achieve one common end goal? Isn't there something resembling a "universal" set-up, at least to use as a starting point (OK, that's two questions)? Especially since the 944-968 family has been tracked for several decades now.



I realize that tracks differ greatly in layout, which of course can influence the car's set-up, but when I say "get around a corner on a track as quickly as possible," I mean a reasonable variety of corners that drivers are likely to encounter at most tracks. I also realize that different people may have slightly different interpretations of condition 8), but still, I would think the above boundary conditions would cover such a large majority of people who are serious about tracking their car, but can't afford or don't have the space to store a truly dedicated track car, that by now, a BKM (Best Known Methods) set-up surely must have evolved into being. However, despite the fact that I haven't read many heated disagreements about suspension set-up on these cars, I really haven't come across a BKM set-up, which strikes me as very odd. Thanks.

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[flash]

there really aren't ................ sort of



what you describe is a dual purpose car - what others are talking about is a track setup



in a dual purpose car there are a few variations, depending on your personal tastes and limits - what one guy thinks is too harsh is tame to another



for a dual purpose car i would keep the springs down below 400# net wheel rate at any corner, and likely more like 300-350 (which is where i am now)



sway bars i find to be better are the ones i have, which are about as much stiffer than M030 than M030 is over stock



shocks and struts are subjective - i find that hydraulics work much better at dual duty than gas - this is why i spent the extra money to get dual adjustable hydraulics all around



i wish you were out here - i'd let you take the car out and see for yourself

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[Cloud9...68]

Yes, I'd love to find an excuse to go out to the 968 mecca that is Southern California one of these days and sample a well set-up 968 or two.



What I'm trying to describe is a car whose primary purpose is as a track day car, that may possibly be used in club racing, that isn't a daily driver, but can still be driven on the street (to and from the track, if nothing else) on occasion, preferably located in a town with smooth roads. Correct me if I'm wrong, guys, but I think this pretty well describes Firefish's and Craig W's cars.



So, after all the experience with tracking these cars, the only universal truths are:



- The more bracing, the better

- Monoball spherical bushings and polybronze spring plate bearings are a very good thing

- Get a set of R compound tires

- LSD is always good (somebody could REALLY get the wrong idea from that statement...)

- Lighten the car as much as you can get away with



Considering we're dealing with Newtonian physics (nothing quantum mechanical), and only one type of car, I'm surprised the the above list doesn't include a pretty tight range of spring rates, sway bar diameters, maybe a different set of shock bump/rebound damping rates for gas vs. hydraulic, and a fairly common set of alignment values. But it sounds like suspension set-up is still more art than science.

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[flash]

pop out for the paso robles run or detail day or.......................



then you will have a frame of reference

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[savvas968]

just my 2 cents here,for those that are willing to consider,which i believe the original question was all about.



Running a DUAL PURPOSE 968,with about 265 hp,spec AL flywheel,turbo rs LSD,manual ,3 inch through exhaust and big reds,std 175 rr torsions

9JX18 ,240/640 FR MICHELIN CUP slicks fr ,270/650MICHELIN CUP on 10jx18 ,I found after several experiments with KONI,

bilstein,eibach ,spax and others that the best compromise set up to be the following.



MO30 fr and rr roll bars with delrin bushes and rod attachements to the arms.REAR rollbar at the softer.

951 cup car fr and rear coil over shock/struts with 500/550-600 rr/fr spring rates.

couple of negative degrees camber in the front on the camber plates and throwing way the std castor blocks,made the car

cornering more flat at speed even at 120 degree bends.

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[Cloud9...68]

savvas968,



Your car matches what I envision mine to become soon very well. Thanks much for the recommendations. When you say 951 cup car fr/rear coilover shocks/struts, what brand are they (excuse my ignorance)? Or will any reputable shop know the specs on these?



Not that this is my primary concern by any means, but how did you suspension set-up affect the ride quality on the street? I don't care for myself, just wondering if any potential passengers will end up boycotting the car <img src="/forum/images/smilies/968/tongue.gif" class="smilie" alt="" />

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[Cloud9...68]

savvas968,



Just thought of another question: When you say you're running a 500 rear spring rate, I assume that's the combination of the torsion bars and the springs associated with the coilovers, right? So that would be a 325 lb/in helper spring at the rear, correct? Thanks.

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[flash]

remember the effective rate conversion factor - any coil spring in the rear is only 56% effective, so you have to calculate accordingly

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[Cloud9...68]

Yes, good point. So that would equate to about a 580 lb helper spring (325*1/0.56), which when added to the 175 lb torsion bar, would give a cumulatiove spring rate (assuming the two are directly additive) of 500 lb/in. But I assume nobody makes a 580 lb spring, so a 600 lb spring would then produce a total wheel rate of 511 lb/in. Did I do that right?

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