333pg333

Good posts guys and I tend to agree with Skip that recent advancements can allow us to make changes to the Factory setups from yesteryear. Also the state of the track itself will dictate suspension travel too. Some tracks we run on are pretty bumpy and having the high speed release valves in the KW's help a great deal. You don't have to suffer wallowing of too soft springs or bounce-skip of too highly sprung setups. Modern technology has progressed from Escort Cup setups.

951and944S

Don't forget that many people today still run the old Escort Bilsteins too, not comparable to multi adjustable remote dampers, but fairly competitively.

Advancement in tires is probably more responsible for lowered laptimes more than anything else.

If you took a factory series turbo cup car of Jacques Villeneuve or Scott Goodyear as it was setup back in the day and fit modern tires, it'd be competitive in it's respective class in my opinion.

The mathematical formulas are not witchcraft, they're legit.
The effective wheel rates are what they are.

T

333pg333

The formulas may be legit, but it would still seem that there are people at odds with the applications?
Speaking of formulas. For the guys still running with torsion bars due to costs or class restrictions, working out the effective rear wheel rate is something you see some disagreement on. So some people may be factoring in the wrong effective spring rates into their front to rear equations?

Skip Wolfe

I'm one of them. Fairly is the optimal word

Agreed

I do not agree. Most of the guys that race the Escort Cups upgrade suspension - shocks, spring, and sway bars unless prohibited by class rules. Running the original suspension would pu them in mid-pack barring unusually high driver talent

Agreed - just need to make sure your are using the right formulas. Using the wrong multiplier will lead to the wrong answers/conclusions.

951and944S

I know these type discussions draw you two (333) in because I've seen both of you in similar threads going way back.

I don't think we're disagreeing much, it's just that, being around tracks as much as I am, under cars of 944 competitors, I see some setups that seem to work perfectly fine for the particular driver and I'm thinking to myself......WTF....?!?!?!

It's not even unheard of to see a rear rate of up to 1100 lbs/in and whether you believe the factory wheel rate ratio of .54, .60, whatever, the fronts would have to be 2000 lbs/in to mimic factory fr/rr balance.

If you think seriously about rates like those for a second (even factoring a much less stiff front), say 1000 rear and 800 front, you're talking about nearly 8000 lb/in of load necessary to compress the suspension just two inches assuming the springs are linear.

Like I said, I've done alot of research, looked at alot of cars, gotten alot of feedback....., my opinion is - these type rates aren't necessarily better suited for anything other than initial turn-in roll time reaction and much of the suspension feel/movement ends up coming from the tire sidewall (think kart).

Just two different schools of thought.

While I can't vouch for Pete's story about his friend's 'Ring times, I can take him for his word as anyone else here that I don't know personally.
Examples like that, with factory proportional setup is just as valid as someone following a totally different line of thinking and they both seem to produce equal results.

It doesn't seem cost effective though to invest a ton in quality suspension parts, i.e. - sphericals, hinge bushings and most of all.....$4500 dampers to control movement of components that will rarely move more than .500-1.00 inch.

Interesting and valid points though guys.....I enjoyed it,

T

Oddjob

That is why this topic gets beat to death, and never to any solid consensus. Yes, there are all sorts of ways to setup the suspension, and variables to tinker with. Everything has an impact. Shock valving, spring rates, sway bars, bushing material, alignment, ride height, weight and weight distribution (corner balance), wheel width and diameter, vehicle track width front/rear, tire size, tire brand/type, tire pressure, open diff, LSD, or TBD, what loaded lock%, what unloaded lock%, engine output/torque curve, chassis stiffness – bars, cages, etc, aerodynamics, and so on…

What is the use? Street, autocross, DE, racing. Some of each? What type/length of track? CW or CCW? What type of turns are predominant, fast sweepers, tight decreasing radius turns, etc? Are you going to change your setup depending on each track you run at, or will it be a compromise to be used at every track? You would not want to use the same setup for an auto-x as you would running Daytona. One setup can be prone to understeer at very low speed and oversteer at very high speed (although I have not run into the opposite)

Driving style: Trail braker? Late apex line? Do you like a loose car or do you prefer a car with a slight push? This is a big part of the puzzle – personal style and preference.

Keep in mind that professional race cars will be setup differently for each track, and the same car will also be setup differently for different drivers – so with endurance racing, where you have multiple drivers, they will compromise the setup to be most accommodating to the various drivers.

Point is, there is no absolute correct setup for a 944, for all drivers for all uses.

From my experience, I think there is some change in balance at different spring rates. A 944 with stock spring rates seems to be balanced around a 1:1 front to rear effective spring rate. But as the spring rates increase, the balance tends to swing more towards a front bias.

With PCA Racing (the most common venue for 944s in north america), most of the 944s are running in the stock classes, so that means stock weight, and within reason, somewhat stock weight distribution. I have no insight as to how the competitive europeans are setting up their 944s.

Oddjob

For the guys matching the factory setups: exactly how are you doing that?

The factory spring rates for the various Turbo Cup springs and for the barrel helper springs on the back of the 968 M030 shocks (which are the same springs as used on the 86 Turbo Cups) are not absolutely known. They are all progressive springs, so there is no single linear rate. Published numbers for both the front and especially the rear springs are all over the map. So until there is absolute confirmation of the exact spring rates of these springs, its hard to copy the factory spring balance.

Also, understanding the effect of progressive springs, front and rear, and the rears combined in conjunction with torsion bars (anyone here know how the factory indexed the torsion bars when run with the rear helper springs?) is more complex than running linear springs front and rear w/o torsion bars. How the actual spring rates change over the range of motion when the car is diving/lifting and rolling, what impact the varying spring rate has with respect to the static shock valving, and how all that changes the handling balance into and through a corner is an unknown to the average amateur.

So unless youre using the actual factory Turbo Cup springs, shocks (either the Turbo Cup Series Bilsteins or the old US Escort Series Konis), and swaybars, Im not sure how close you will actually get to the factory suspension/handling balance.

Also, I can understand the point of trying to match the Turbo Cup suspension for use on a track car. But Im skeptical that matching stock street suspension, then multiplying the assumed rates by 3+ times, for use on a track car, is good logic. The M030 suspension, is a sport suspension, but it is still for street use. Its not race suspension, and I think the factory suspension setup/balance between street cars and Cups may vary quite a bit (for any version, from 944, 964, 993, 996 and 997).

Oddjob

Pete,

Where did you find specs on the barrel spring being 100 lb/in?

400 fr/ 850 rr sounds like it would very much be a tail happy car, and very well suited to auto-x'ing; so that makes sense that your friend is successful at auto-x with that car, and prefers that type of setup.

I cant find it in the link, what spring rates do the H&R setups come with?

Regarding your last comment about compensating handling with tire sizing - you are running 235/295? Considering the factory setups were 205/225,225/245, and 225/255, have you tried your car with less tire stagger?

Skip Wolfe

Jim - can you confirm 160# front spring rate. I thought the Turbo S was 175# and would think the Club Sport would be equal or higher

Skip Wolfe

I think we are agreeing on most of this as well. As I said, there a lot of guys (myself included) who will adapt their driving styles to whatever they are driving and be almost if not as fast.

My point about Pete's buddy is that he is running front to rear ratio of 1:1, not the Porsche ratio of 1:1.5 that Pete stated. 1:1 is not that uncommon and can easily be compensated by sway bars, shock settings, tire stagger, and driving style.

Oddjob

The Turbo S/M030 front spring is 28 N/mm, which does convert to approx 160 lb/in. The 968 M030 (CS or not) used the same front spring.

So confirming the actual rear barrel/helper spring rate is critical to comparing the spring rate balance.

The other unknowns comparing the Turbo S to the 968 M030 suspension, how were the torsion bars indexed on the 968, what is koni shock valving front and rear (the fronts are different part numbers), what is the effect of the larger 968 M030 sway bars on balance, and any slight differences in the vehicle weight distribution. The 7 & 9 x 16" 225/245 vs the 7.5 & 9 x 17" 225/255 is probably not real significant.

But, as I mentioned above, Im not sure how relevant it is to determine spring rate balance on a factory street car, when you are building a race car that will be running 3-4 times higher spring rates, and used for a dedicated track application. Maybe not a bad rule of thumb for stiffening up a DE/Street car, and it may give you a ballpark starting point, but I dont think it will get you right on target for a race car.

Skip Wolfe

I agree with you Jim - was just curious.

renvagn

Ian,

Jim presents all good information. There are numerous set-up theories out there. I suspect some of these very high spring rates (650 -700) that you hear of are making the car lose compliance over bumps and not allowing the cars shocks to work properly. Furthermore, I believe many drivers attempt to decrease body roll by beefing up the spring rates, further causing the car to skip lateraly. These cars need a little rear roll, then they set and shoot forward. Too much rear spring makes them edgy and want to walk out quick.

RS Barn is developing a set of F & R bigger sway bars to address this issue of body roll, which is what the Cup series had. More so , if you haven't put the bigger bars on the car, they really help the car to rotate significantly better.

If you have a frequently street driven 951S but want the slop taken out of the suspension. Keep your T bars. The turbo cup suspension is not a bad way to go. You will want to get the upgraded control arms and camber plates, bilstein turbo cup struts, find the original progressive turbo cup springs, get the 968 m030 30 mm and 19 sway bars, set the ride height, bray kraus castor brace and get the car properly alligned like Skip mentioned. You will have a very neutral handling car which provides controlable throtle on over steer. This set up is a very nice DE track package until you max it out in the corners once you hit the advanced run groups. Also I like the 16" or 18" wheel packages. 17 inch wheels IMHO are for looks on the street and are not the preferred track size do to making the gears tallers creating more lag off the corners, which non of us want.

Call Pete at RS Barn 215-968-2599 he has set up two firehawk cars this year, plus I just recently converted my progressive springs to linear and the car was 2 seconds quicker at VIR. The initial front rates you mentioned are far to low. Maybe somewhere in the area of 350 - 375 F linear and what is calculated for the rear based on your T-bar size, or just get the turbo cup springs F & R. Good luck, it is a complicated decision.

333pg333

renvagn, my point being that with the advances in shock technology you don't necessarily have to compromise. In other words you can have quite high spring rates and not bounce skip all over the track when encountering bumps/ripples. In the past you either had compliancy or grip. Not both.

billthe3

What would you guys recomend for a new front spring to match the stock t-bars? Would a 250 front be to much with adjustable camber plates? Or would something closer to 200 be better? (How low do the 2.5" hypercoil springs go?) What is the spring rate of the stock rear t-bars for an 86 anyway?