Most questions I have I can find the answers to by searching, but I'm coming up with nothing on this. These pics show the way Porsche measured the ride height on the 911 by measuring the spindle centerline and the torsion bar centerline. Are there specs like this for both the front and back of the 914.

All the reading Ive done on ride height has been related to measuring to the rocker, donut on the floor or fender lip. Im interested in the geometry Porsche used for the road cars, and also what they suggested for racing. Any link or book would be appreciated.


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You know this is an interesting question because I did the same thing recently when I re-did my whole suspension. Setting up suspensions is relative to many different things.

I know the stock specs are available, however I don't believe anybody uses them. The stock tires are coming harder to find and set up from the factory it wasn't optimal for handling that the car was capable preforming at.

I used the setup in Scruggs alignment procedure I'ts here on the site. Recently I have been playing around with the camber in the rear suspension.

Yes, if you look in a Haynes manual there are specs, same as the 911 method.
If not Haynes then Bentley and certainly the 914 factory manual.
I have seen it in both factory and Haynes manuals.
It is very clearly a relationship between the pivot point of the system and the centerline of the wheel, so tire size is not relevant....just shod be the same diameter front and rear.

For racing, the setup is quite different and you should confine your searches to the offroad and racing forum here....it's really quite different and really depends upon the track, your wheels, your engine etc...

Rich

The rear of the 914 is not the same type as the 911. Coilover shocks going
to the trailing arm. With stock shocks, there is no adjustment of ride height.
With aftermarket shocks or collars you can move the perch to adjust the height.

Thanks guys. I'll look up that alignment thread tonight. I understand the factory parts have limitations. Rear height adjustment would be factored in to my plan . The goal is to have an optimized street car with small flares. I have already assumed the guys who are raising spindles and moving rear trailing arm points are beyond the normal street/autoX setups are running big power, big brakes and big tires.

Adjustable rear shocks (koni) with adjustable perches using smaller diameter springs is the right way to go if you do not plan to change the overall suspension geometry in the rear. If you do not have some method to adjust the rear springs, you will never be able to corner balance the car properly.

In front, you won't need to raise the spindle for a street car, you can go really low on 205/50 tires and lowering the front adjusters....too low for a street car to do speed bumps and holes, so there is no need to do raised strut.

I hav had my car as low as it can go with all stock front and rear suspension, and adjustable rear shocks. It's way too low for a street car...and I ended up raising it up a bit to deal with bumps etc.

Rich

From the "914 Technical Specifications Booklet"

Front

Ride Height: A-B=90mm +/- 5mm
Total Toe: +20' +/- 10'
Camber: 0deg +/- 20'
Caster: 6deg +/- 30'

Rear

Ride Height: Fixed by Spring
Camber: -30' +/- 20'
Toe: 0deg +15'

Tire width will weigh in on how you want to set the suspension geometry.

With that said....I would definitely recommend adjustable perches in the rear.

Positive toe in front might work fine with 4 inch wide rubber, but sucks with normal width modern tires.

Same in rear...

17x7 and 17x8 was the planned wheel size with 205-225 and 245-255 width tires. I have read the positive toe isnt good for modern wheel/tires.

There is a few threads that touch on the connection between roll center and roll stiffness and the changes that occur when a 914 is lowered. If the RC gets too low, stiffer springs and bigger sway bars are needed to keep roll in a corner under control. This could lead to a stiffer than necessary ride just to be "in the weeds".

Now I'm the first to admit I know just enough to be dangerous, but its the basis for asking what the proper and sorted geometry would be. I'd rather have an inch more ground clearance and a compliant ride that a cooler looking car that rattles my filling out.

914 teener: are you suggesting to make the pivot points on the rear suspension adjustable up and down to adjust the trailing arms angle? Or just to have adjustment for camber caster and toe?

Now maybe this is overthinking thing a bit too much, and if so, please say so. No need to ponder things that dont matter. :-)

I am also having a hard time finding Scruggs alignment procedure. Anyone have a link or a search phrase?

No...not the pivot points... the shock perches. As Rich has stated this adjusts where the spring will load and unload. It also affects the "ride height"..but ride height is a consequence of how the suspension geometry is configured. If you just want to lower the car so it looks cool....that's a different question

It really depends on the way you want to drive the car and what handling characteristics you like. Feel...not think. There are a lot of dynamics that affect this...Roll centers...pivot points.....springs rates ect.

I'm an engineer so.....if we get into the math it isn't linear....meaning in a straight line. When you start talking about springs M x A = F doesn't apply in that fashion.

If I am reading your thread right you plan on running flares with those size tires.

So is this car currently set this way or is this your plan? What do you think you want to do with it?

Just my experience for a street car that I setup for pure autox, now back to street.

The front control arms should never be horizontal. The ball joint should always be lower than the pivot point. You can get pretty close, but never level or more....it creates bump steer and ruins the geometry.
If you feel the need to go that low, you need raised spindle struts to keep that steering geometry correct. For now, shoot for slightly lower on the ball joint side...

Then, for looks I like about 3/8 inch rake so the rear is a bit higher.
Simply measure the front and rear of the rocker panel to a level surface.
Once you have the look you want you will need to corner balance the car which may change things....but you need to start somewhere.
Now, in reality the car will handle better with the front about 3/8 inch higher than the rear' but it will look odd to most people.

For toe in at front I use a total of 1/8-1/4 inch overall toe IN at the front
In the rear, I use abut 1/8 in total toe IN in the rear.

Now, for autox, toe OUT in front and rear makes turning in a whole lot faster and easier....almost like cheating...
BUT! It sucks to drive on the street....can be done, but it sucks
It also will wear out the tires quickly.

Rich

so what's your backlog for an alignment at this time

Hopefully this attachment will help.

It might if it worked!

914 teener; Like i said, I know just enough to be dangerous. Definitely will be welding on flares.

I have a '74 that I am collecting parts for, planning for, and working on. I have the wheels off a boxster s sitting beside the car (I have some of the 5 lug parts already, and will probably need spacers). I would say the end result would be a mean street car/autoX-er. Something my wife will hate to ride in, and my buddies will mess their drawers in!....On the other side of the garage is a 05 Legacy GT with a ej255. I've already started dissecting the wiring.

I have done a few muscle cars myself and watched friends also try and build a project without a plan. It never goes well. This is my thought process of what I need for suspension. Parts-wise, knowledge-wise and also reference materials.

Orbit; thank you for that pdf!

r towle; that sounds like a sound plan to follow. Follow whats known to work! Thank you.

It's something you can learn to do at home.
Happy to show you, and happy to help.

Rich

Wow...well sounds like fun.

If your are talking more sprung weight I would seriously consider talking to Chris Foley here about reinforcing the trailing arms and or chassis with increasing the horsepower and speed as this changes the dynamics on the chassis itself.

I think you are doing it right. I did the suspension first and the 914 is a really cool platform to play around with being mid engine.

It definitely is a cool platform. This is my first project outside 60's Gm muscle. It's a steep learning curve, and I love it!

Low power
Tunable suspension
Momentum driving.

Take the time (and money) to setup the suspension, get adjustable rears, and get it aligned and most importantly corner balanced.

You will love how well this car handles when it's done right....4 -6-8 won't matter unless is planted...then it's just an amazing car to drive.

Also, spend money on brakes....a setup you can stomp on with total confidence that nothing will fail....then you can drive fast and know you can stop.