Help with suspension setup!?!
 

Ive gotten to the point of wanting to order parts.... and found I really dont know what the heck to order.

My car is a '69 911S, with 2.7RS MFI engine. It is on a diet and should weigh 2000-2050lb. It will be used for track days, some autocross and some street driving. It is not my only car or even my only sportscar and thus track use will be its primary mission. Im also a masochist and dont mind sacrificing ride quality for handling.

Im getting lots of varying advice. Im hearing from Smart Racing Products that I should go with Bilstein struts revalved to their specs, 23mm front and 30mm rear torsion bars, their "27" front and rear anti-roll bars, adjustable spring plates, rear monoball, and of coarse new wheel bearings etc.

That sounds pretty dang stiff to me.

What type of front camber plate with monoball should I run and what kind of strut tower brace should I run with it?

Im converting to aluminum rear control arms. Is there any way to tell from teh arms I have what year they are, exactly which wheel bearings I will need and what other parts are required (half shafts.... ???)

Who is a good source for parts on all this stuff? My criteria are: price, experience in putting together a total package and helpfullness.

What rear bar should I run? If running stiffer torsion bars (like 30mm) it seems I would run little or even no rear anti roll bar?

I want a car that gives precise handling, is neutral with mild oversteer on the edge and that instills lots of driver confidence. (I know... we all want that!)

All ideas and suggestions are welcome. My budget for this project is $4500 - $5000. The car currently has all its stock stuff including koni struts. It does already have new front A-arm bushings and ball joints but everything else will have to go.

I would call Elephant Racings' Chuck and discuss these options with him. He offers some different twists on the same stuff as Smart and the parts are available through Pelican. I think Steve Weiner in Portland is very knowledgeable as well.

Craig Watkins at S.R.P. knows what he is doing. I would also suggest you give Steve Weiner at Rennsport systems. Alot of people here speak very highy of Elephant racing bushings too.

Craig is an engineer as I recall. That makes 2 engineers involved in the Pooschey aftermarket biz....

I did speak with Chuck at length. Great guy, lots of good suggestions I will definitely have to buy some stuff from him!

The more I look.... the more it hits me: this stuff is EXPENSIVE!

I'd suggest you go with Chuck's stuff.
He's got good quality parts and his prices are good.
I just installed the swaybars, tbars, polybronze bushings and monoballs last week and it's really nice!

I think 22/28 tbar would be a good combo for your car/goals

You might also consider adjustable yellow koni's instead of bilstein dampers (since you already have koni struts)

cheers,

Jeroen

A friend had stiff torsion bars in his '69 track car and he went back to softer ones, at least in the rear. He's using my old 25mm rear bars now.
-Chris

I thought this would be just the opposite. Shouldn't everything be beefed up as the spring rate increases? I had a car that was professionallt set up. It had 22mm front and 30mm rear torsion bars, TRG adjustable sways and Bilsteins revalved by Smart Racing..

I know of a 914 which weighs something like 1500 lbs, that is receiving front coilovers because front torsion bars thicker than 23mm would bend the front control arms. Apparently, 23mm is not stiff enough. At some point I wonder why guys don't just weld axles directly to the frame. Just kidding, but kinda not kidding. Real stiff race cars feel like the axles are welded to the tub.

Jack Lewis based here in Atlanta runs a really trick HSR 2.0 '69 911. He wins. Alot. Extremely fast.... he turns 1.40 at Road Atlanta in a 2.0 car. He runs no rear bar at all.

I have read "Tune to Win" by Carroll Smith and done some study of suspension dynamics theory. In short: loose gives more grip. This means that in theory less stiff T-bars and roll bars would yield more grip. This however does not work in practice because loose also gives less control. Suspension geometry changes under load are allowed with a loose setup and these more than negate any grip advantages associated with the looser setup. So the ticket is to find the magic balance between as loose as you can go for grip, but as stiff as is required to maintain control of geometry. In theory.

My understanding of a 911s suspension geometry and base setup is that it leaves something to be desired. Because of design limitations, you need to run a pretty stiff setup in order to gain appropriate control. To really get the best... this is why folks relocate the suspension mounting points.

Regardless of all this.... Im still contemplating what to go with as an overall package. 21mm front and 28mm rear OR 23mm front and 30mm rear. The latter does seem terribly stiff for a <2100lb car. Then there is of coarse the BIG issue of exactly which Bilstein valving to go with??? I am going to go with raised spindle RSR struts, but its a shot in the dark on which valving to choose with which torsion bars.

JMZ: Craig at SRP may be a great engineer and im sure they sell fantastic stuff... but neither of the 2 girls I spoke with when I called knew anything more about suspension setups than what they read in the SRP catalogue. They could not answer any of my more detailed technical questions. Craig nor any of the other real experts available. Nobody has called me back as promised. Having all the best parts and knowledge in the world is worthless if the customer cannot access said knowledge!

Terry

I've been very happy with Smart Racing Products. All of their parts come with great instructins and are engineered great.

I just assembled my Smart Racing front antiroll bar last night. Piece of cake.

They can provide everything from raised spindled struts to spherical bearing kits. They are very knowledgeable.

http://www.smartracingproducts.com

Terry;
Since everyone has an opinion on this (as you're finding out) and you can easily spend 2X your budget based on other people's recommendations, my recommendation is to go back to basics. I think Carroll would agree.

1) Based on your current experience with your car, what are the SPECIFIC issues that you'd like to address with the handling? Is it too loose or too tight? (Your from GA, so you know what "tight" means, right?) Is it consistant?

2) When does it do it? Fast turns? Slow turns? Corner entry/mid-corner/exit?

3) What sort of surfaces? Rough? Smooth? Off camber?

Based on your response maybe we can trim the budget down to a number that will leave some dollars for more track days which will reduce all of our lap times! ;)

Terry- I think you should use the word "soft" here instead of "loose", as "loose" is associated with an oversteering setup and could make the discussion confusing.

Quote:

Then there is of coarse the BIG issue of exactly which Bilstein valving to go with??? Nobody has called me back as promised.

Call Bilstein, USA. People have had good luck in getting answers on valving for different Porsche setups directly from their engineers.

TT