Hi,
I'm just about to have the suspension set up on my 914-6 GT project and wanted to see if anyone had any advice. I have never done this before (my first 914) and was looking for a fast road/track set up. I think the range of settings people seem to talk about on Toe and Caster is fairly small but camber settings vary wildly depending on what people want to do and type of tyres.
I know the theory about track set up and measuring temperatures across the width of the tyre but this car will spend more time on the road than track (albeit I could be called a spirited road driver!), and tracktime ain't cheap !
Suspension components are :-
FRONT -
Sway-a-way 22mm hollow torsion bars
Weltmeister 22mm sway bar
Bilstein shocks
Weltmeister camber plates
Fuchs 7X15s with Goodyear Eagle GSD3 205/50s
REAR -
Weltmeister 140lb springs or 180lb springs available - need to decide which ones are best to use ?
Weltmeister 16mm sway bar
Koni adjustable shocks (yellow)
Stable Energies rear strut tower camber brace.
Weltmeister chassis and suspension arm stiffening kits
Fuchs 8X15s with Goodyear Eagle GSD3 225/50s
Tyres will be

This is what I was planning to do based on some previous indications:-
FRONT -
Toe in(each wheel)- 10'
Camber- 1 degree negative
Caster- 6 degrees
REAR -
Toe in(each wheel)- 15'
Camber- 1.5 degrees negative

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I think these are the factory settings -
FRONT -
Toe in(combined) 20' +/-10'
Camber- 0 degrees +/-20'
Caster- 6 degrees +/-30'
REAR -
Toe in(each wheel) - 0 degrees +15'
Camber- 30' +/-20' negative
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I would welcome any advice or opinions. If anyone has any advice on initial settings for the rear Koni shocks then that would be a real bonus. All advice gratefully received and without prejudice.
Andrew

Your alignment seems OK for a start tho if you have rubber rear bushings, you may need more rear toe in for braking stability on the track.

Your choice of 22 mm Tbars makes an out of balance condition with your choice of rear springs (IMO). I would think that 200lb rear springs at minimum would get you closer. If you don't have threaded collars for your rear shocks, I would get some.
The stiffest rear springs I could find using the stock perches were 200lb and they were twice as expensive as those that go with the threaded perches (2.5in dia).
You need the stiff springs to help keep the inside rear tire on the ground. Weltmeister rear springs are progressive and these are fine for the street, but suck for the track.
Spring rates that change= handling that changes....not good in mid corner. The rear anti roll bar exacerabates the inside rear lifting....something to be avoided at all costs. On my car, for instance, I run 21mm Tbars with 275 or 300 lb rears with no rear AR bar.

I've never ran Konis so I can't offer any advice there.

Don't worry the tires you are goingt o use will keep you out of trouble.
The stiffer suspension and street compound will have you sliding the front or rear way before you get going too fast.
And they won't tolerate more than 15 minutes of sliding before they greasy and start chunking.

For a car that is primarily a street car, I'd ditch the 22mm torsions and go back to stock, or slightly bigger (1mm?) than stock. That and your large sway bar would help keep the handling pretty even.

--DD

I agree either you need to soften up the front or jump to at least 200 lb rear springs. My car has 19mm front torsions, 22mm front bar with 250 lb rear springs and it understeers a bit.

Thanks for the advice.
Is 15' toe in on each wheel at the rear enough ?
I will check again to make sure the 22mm hollow Sway Away torsion bars are fitted. The guy I bought the car off said they were fitted but I havn't checked.
Seemsto be a fairly common opinion that my front would be too stiff or my rear too soft with my current set up.

I notice no one has made any comments about the camber settings- To much ? Too little ?

Are the hollow 22mm Sway Away torsion bars as stiff as solid ones ?
I understand that the majority of the torsional stiffness is in the out edge but I would have assumed that hollow ones were fractionally less stiff than equivalently sized solid ones ?
Just checked the Sway Away website and the 22mm ones are their 'mid range' ones. They do 21mm, 22mm & 23mm. They do the same thicknesses in solid bars as well. It was on this basis that I thought the 22mm ones would be OK with the 180lb springs on the rear. I am a 914 virgin so any further comments/advice gratefully received.

Many thanks
Andrew

The hollow t-bars will be fractionally less stiff than the solid ones. They might (not sure) be fractionally larger in diameter than their "rated numbers", which would make up all of the difference.

You can do the math if you know the size of the hole in the hollow bar: The bar's effective spring rate is based on the fourth power of the diameter. The hole would take away the fourth power of its diameter, which turns out to be very little in comparison to that first number until the walls of the bar are very thin. (If the hole is half the diameter of the bar, it only takes away 1/64th of the strength!)

Since the effective rate goes up with the fourth power, you can see that going up one mm does not result in nice even linear steps...

--DD

Camber is pretty dependent on how you are going to use the car and the type of tires you will be using on the track. I run roughly -2.5 to -2.75 and some say thats not enough. In my opinion anything under -2 with DOT R tires isnt enough - especially in the front.

Andrew,

One comment about the camber ... it would be slightly unusual to be running more negative camber at the rear than the front.

Have fun with the car!

Scott

You're right. Just checked the Sway Away website and they are actually 22.5mm diameter with an effective rate of 22mm. I don't have the bars out to measure them but based on your fourth power maths assumption then for the 22.5mm bar to have the effective rate of a 22mm bar, there must be a a 12.5mm hole in the middle. Sounds about right.

Sway away do 21/22/23mm effective rate bars. If the 22mm bars are most compatible with >200lb springs on the rear then it sounds like their scale of application is very top end biased if std 914 springs are about 100lbs.
I think I saw someone write that std torsion bars are 19mm. That being the case then 22mm bars are 80% stiffer than std. 180lb rear springs are also 80% stiffer than std. Seemed like simple logic to think they they should be fairly compatible. Is there some reason why this would not be the case ?
Andrew

Very interesting comment ! I had put a less detailed post in the 'Garage' some time ago and more than one person indicated that regardless of absolute camber values than a rule of thumb was that rear camber should be 0.5 degrees more than the front. I was applying this previous advice which matched . Is this not correct then ?
Would you suggest similar amounts of camber front and rear or are you actually suggesting that it should be the opposite way round !!
What is the logic behind this ?

Andrew

Problem with that logic is the stock car understeered something terrible at its upper limits. Now you have fat rear tires. You need some extra help to get the car to turn. Its not going to be terrible with 180's in the rear, but I can almost garuntee if you're driving the car at limit it will push on some turns - especially if you plan to ever AX the car.

Makes sence. Given I have the current parts installed then I will try as it is and see what it's like but I'll know what to do if it is like you suggest. What are your thoughts on the relative front to rear camber difference ?
Another piece of information I picked up was the comment that too much front negative camber compromised braking power. This seemed to support the 0.5degree less front camber philosophy ?
As you can see from my original post I'm not running Dot R tyres, just good quality sports tyres. Do you thinik running >2degrees will 'significantly' wear down the inner edges in road driving or is it still a practical compromise setting ?

I think you are at the point where you probably have good baseline settings for a street car.

Give it a shot. Perhaps for your driving style this will be fine. I think my car has had about 8 different setups in the past 5 years.

When you're at the track take tire temps from inside to outside. You'll very quickly know if you have enough camber. It sounds like this car will see more street miles so less aggressive alignment and spring rates will probably be best way to go.

Thats a first

Nope Grant is right, my rule of thumb is document everything, and then go from there once you have the base line and know what it will do you can move an see where you need to go. Bu until then it is all guess work.

BTW, suspension setup is like underwear we all have preferences. So what works for some other find unconfortable.

A tire Pryo will tell you more about what you are running and how it is set, but DOT-r are diferent than street tires, and way different than race slicks. IF what you are doing is all street and one auto-x a year don't worry so much. If all you do is auto-x and then street to get there and home, Then worry about it some more. But until you drive it and see what works for you, you will never know. Smartest thing you can do is drive the car. The rest will come with real data that being on a set of jack-stands can not provide.

BTW, a true good auto-x setup might not ( probally won't) be optimal for the street or the track.

There is no silver bullet for this one.

Also if you can get pictures of your car as it makes turns both left and right, video is even better. That will give you an idea what the car is doing, and more importantly what the suspension is doing. Last weekend I stiffened up the front and rear, and started carrying the front inner some corners and rear inner on others. So it now back to the orginal bar setup, which did not allow the tires to lift, and provided faster lap times. But with out pictures I would not have had proof that it was happening, I know what I felt, ( driven FWD cars ) so I know how to hang a rear tire in the air, pissing dog style. But pictures and times told the story.

I'm intrigued. What exactly is auto-X ?
Is it some kind of mixed surface racing? We would call that Rally-X in Europe.

This car won't see the rough stuff.
Tight UK race tracks, hillclimbs and sprint events on variable tarmac surfaces.

Also planning to do some long distance rallies in UK and across Europe which involve odd speed tests in various types of venues from car parks, to race circuits to farm yards.

From comments so far it sounds like I should go for mild negative camber of about 1 degree all round and about 10'-15' toe in on each wheel, front and rear.
The original manufacturers settings were 0.5 degrees of camber on rear and none on the front. Seemed like another bit of simplistic logic to stick to this front to rear differential on first set ,up but no one seems to have supported this philosophy so I'll drop this. Please speak up if you think I have misunderstood things.

I understand the comments about measuring tyre temperatures at the track but might not get on track until next year and just want to get it as close as I can based on the best advice from you guys who have experience.

Auto-x "Autocross is a form of motorsports that emphasizes safe, low-cost competition and active participation. An autocross is a timed competition where drivers navigate one at a time through a temporary course marked by traffic cones, rather than racing on a track with multiple other cars, as in road racing or oval racing. Autocross tends to place more emphasis on car handling and driver skill than on sheer horsepower, and events typically have many classes which allow almost any vehicle, from economy sedans to purpose-built vehicles, to compete. Speeds are slower in absolute terms when compared to other forms of motorsports, usually not exceeding highway speeds, but the activity level (measured in discrete turns per minute) can be higher than even Formula One due to the large number of elements packed into each course. Autocross courses are typically 40 to 70 seconds in length. In addition to being a national-level motorsport in its own right, autocrossing is a good way to learn skills that transfer to road racing, as drivers learn vehicle control and club ethics.
Autocross events are usually held in large paved areas like parking lots or airfields. Typically, new courses are created for each event so drivers must learn a new course each time they compete. Prior to driving, a competitor will walk the course, taking mental notes, and developing a strategy to be refined upon subsequent runs. National organizations such as the Sports Car Club of America (SCCA) and National Auto Sport Association (NASA) sponsor autocross events throughout the United States, and many areas have independent autocross clubs. Automobile manufacturers and their associated clubs (e.g. the BMW Car Club of America) sometimes hold marque autocross events."

Unlike Autcross in your part of the world which is akin to a rally stage over here.

"In the United Kingdom, autocrosses are typically held on a grass or stubble surface. In fact the attraction is the challenge of driving quickly on challenging and difficult surfaces. Cars compete individually against the clock, although more than one car may start at the same time if the circuit is long enough and wide enough. Because the course is usually bumpy and there is a risk of contact with other cars, most competitors use specially prepared cars (which vary from very inexpensive to specially engineered racers) brought on trailers. Events are usually held on a region-wide basis, with the RACMSA (Royal Automobile Club Motor Sports Association, now often called MSA)) overseeing rules and regulations."

LOL! I didnt realize you were in UK. AX is timed circuit event around cones. If you plan to do hillclimb you may want to jump to a higher rear spring rate. My car in a recent hillclimb was pushing terribly with 250 lb rear springs (no rear bar) and 19 MM front torsions with a 22mm bar set at soft. I had same size front and rear radial slicks. But again I think it depends on your driving style and the track or hillclimb venue. 914's are great cars as often on bigger courses you can change your driving style to accomodate a car that pushes in the turns.

Camber is fairly easy to change, start at -1 and see how it works for you. From my perspective the 914's dont turn as well with less than -2 degees of camber in competive events with radials. Remeber stock specs from Porsche were for general public - always better to put a car with understeer in the hands of those with a wide range of drivning skills. The 914 will bite anyone who goes into a corner and lifts and doesnt get back on power smoothly regardless of setup.

Its important to note that some of us here only drive track or AX cars so we are a bit jaded. I want the car to turn at expense of car being a bit darty on the street.

You may want to go to 914club.com site and ask there too. Brad Roberts is the suspension guru that I would trust with suspension setup questions. Send him a PM.

Wow ! what a comprehensive definition of Auto-X and Rally-X !

Sounds like Auto-X is a bit like out 'Autotests' but at a bigger venue with bigger turns. Out Autotest events are often very tight involving lots of handbrake and reverse gear going in and out of cone garages.
We also have classic car 'Regularity events' that tour the countryside, sometimes with complex navigation tests on the open road based average speed. These event also feature 'Special Tests' which are more similar to your Auto-X on a variety of surfaces.

Many thanks for all your advice.
Keep it on the black stuff
Andrew

Better than an explanation - here is a video of a local California Autocross (AX) http://www.youtube.com/watch?v=sIicMwEeElY

Looks like fun !