psiegel

I am writing to see if i can get some help from the group in trying to decided which spring to use for my 93 C4. But to do so, I am looking for some comparative data, which will help me to understand the different effects that the various springs will have on the car. So here's where I need some assistance. I am trying to piece together what the spring rates are and how much the springs will lower both the front and the rear of the car from the stock US springs. The springs that I am interested in comparing are:

M033 RoW
M030 RoW
Spings used on the 964 Turbo 3.6 RoW
H & R for the 964

Thanks very much in advance for your help.

Peter

Kahdmus

I recall that I got some good data in this recent thread Please add the H&R 965 springs to your list. I took the recommendation received here and fitted them to my car last week along with Bilstein struts, the difference is simply amazing....AMAZING!!!!!!!!!!!!!!

Most lowering springs seem to lower the car 1.5 Front and 1.3 rear. Remember that you will need an alignment and corner balance once they have been installed.

psiegel

Howard
Not to be dense but just to confirm, Did you install the H & R 965 springs? If so did they also lower your car the 1.5 and 1.3 as advertised?
Thanks

Peter

joey bagadonuts

Here's some more info gathered over the years.

Eibach 964 Pro-kit springs
Front 82.6-250 lbs/inch
Rear 188-256 lbs/inch

H&R 964 springs
Front 190-255 lbs/inch
Rear 220-265 lbs/inch

H&R 965 (Turbo) springs
Front 250-270 lbs/inch
Rear 265-285 lbs/inch

H&R 964 Coil-over
Front 250-285 lbs/inch
Rear 265-285 lbs/inch

H&R 964 Super Cup
Front 455 lbs/inch
Rear 685 lbs/inch

Porsche Carrera RS springs
Front 250-308 lbs/inch
Rear 375-508 lbs/inch

Kahdmus

Sorry Peter..yes they did!

psiegel

Joey
Thanks for filling in alot of the blanks. That a hugh help. Now I just need the Spring Rates and Ride Heights (or how much lower) for the M033, M030 and the Turbo 3.6 (965) springs. Also is anyone familiar with the, "FVD-Sports-Suspension"?

Thanks all

Peter

Hubert

I can't tell you exactly what rates you'll need, or what the values you're looking for are... but I do have a point. Ah... I remember.

In selecting spring rates, lowering your car and and matching the appropriate damper - you should rember to do it in this order: suit the springs to the car, then tailor the shocks to the springs.

In essence (ignoring the anti-roll bars, tire sidewall, damper and other factors involved in roll resistance in the suspension) your car is a mass suspended on 4 springs. When this mass bobbles around on these springs under cornering load, the rate of weight transfer between the four corners that interact with the momentum of the chassis, and the surface, is dependant upon the stifness of the springs. The stiffer the springs , the quicker the rate of weight transfer; the quicker the rate of weight transfer, the more quickly the car responds to inputs of the driver, and undulations of the surface - something you should remember in selecting spring rates.

Most people I know, cornerweight their cars and run (for a street setup) something close to a 1:1 ratio between their cornerweight and their spring rate; i.e., 500lbs cornerweight = 500 lbs spring rate. But your cornerweights need to be determined empircially (on scales) and you should take great car to evenly disrtribute the weight between the left and right tires (i.e., the weight of the cars front should be split 50/50 between the two front wheels; and the rear should be split 50/50 between the rears) - you don't want to end up in a situation where your spring rates/ weight distribution is biased to one side! If this happens, your car will favor cornering one way, but react adversly while cornering the other way.

Once you've determined your cornerweights, and then decided on spring rates. The next step is to suit a set of dampers to the spring rates you'll be using; most off the shelf sport dampers (i.e., koni, bilstein, etc.) are rated to use with 500lbs spring before requiring re-valving (altho even using a 500lbs spring is pushing it). Usually, a 2.25 " spring will compress 1" when the spring rate equals the cornerweight. (This assumes that it is a linear spring; and not a progressive. My comments above relate to linear springs, not progressive.)

Once you've picked appropriate dampers to your desired spring rates, you'll want to have your car cornerweighted and aligned to get the most out of your new setup.

Goodluck.

joey bagadonuts

Hubert,

Very interesting and informative. As for this comment, it makes me wonder if all your acquaintances aren't professional race car drivers?
Using this approach, our cars would end up with 600-lb front and 900-lb rear springs. While there are a few forum regulars who use such rates on the street, the 1:1 ratio may be more appropriate for a track car. I think a 3:1 ratio might be a better number for a daily driver, i.e. 200 f / 300 r springs. Just an opinion.

The best advice I can think of, Peter, is to get a ride with someone whose car has the components you're interested in installed. I could go on and on about the subtle ride differences between various spring models (I'm on my third set) but I'm not sure it would be all that meaningful. Everyone has a different pain threshold and expectation--it's best to figure out yours using someone else's car

Whatever you do, please make sure to replace your original shocks as well, in case you haven't already done so. The Boge's are over 10 years old and well past their prime.

Hubert

That, or they're complete lunatics. No, you're right - my comments came from a more track focused perspective; i.e., to "us" a 1:1 ratio is soft. Some of us run 1:1.3 cornerweight/spring rate ratios and higher. I should have added a disclaimer.

I'm not a Porsche expert ( although I enjoy these forums very much) - therefore, I concede to your personal experience.

However, what most people don't consider is the fact that a jarring ride is often, and incorrectly, associated to high spring rates. This is not true. A jarring ride is almost always a result of a set of oversprung dampers; i.e., too much spring on a damper that can't handle the load. This is why I can (comfortably) use a 900 lbs spring on the street - I've got dampers valved up to 1300lbs springs.

psiegel

Yes I am looking for springs that are for street use only and that will help achieve the following:

Install a system that will help reduce under steer – Install springs with more stiffness in the rear.
Improve aerodynamic stability- Lower front by 10mm more then rear
Improve handling a bit by lowering the car but not too much due to where I live and consequently Winter Conditions.

I believe I am looking for springs as Joey says that are in the low 200 F to low300 R range or thereabouts but the ride heights need to work as well.

I am looking at the spring rates and ride heights so I can understand what I am buying and how it will effect the car. I would love to ride in some P cars with different suspension options but unfortunately were I live there are not a lot of 964s.

I will replace the shocks with Bilstein HD which seem to be the most reasonable alternative and apparently a good match for the springs on the list.

So if anyone has data on the M030 RoW, Springs used for the 965 RoW that would be great.

Thanks
Peter

NotTwinTurboYet

I have the FVD sport suspension kit on my 964. That's perfect! We are several guys using that kit here, and all happy!
In fact the kit comes with bilstein dampers and Gemballa springs (which are made by H&R).
This kit is perfect for road use and not too bad on a track. If you're searching for harder, you can think of RSR springs-dampers, or RS (europe), but it will be more dedicated to track use.
I know that FVD released a new kit (adjustable bound and rebound) but it doubles the price compared to the sport suspension kit. And I know a friend who bought the PSS9 kit, finally he never adjusts it, and the result is close to what I have with my kit.

NTTY

psiegel

Ntty
Do you have the part number of your kit. The guy I talked to said that the springs are made by Eibach and I would want to see if I could get the combination that you got. I wonder if the spring change is the difference between buying the system in Switzerland vrs US. By the way, Do you know how much the kit lowered the car at the front and Rear?

Thanks
Peter

burgass

NTTY
What is the part number of the FVD kit?
Regards

AMG ETR

FVD Sport Suspension for an 89 964:
FVD 333 964 00 - $1495retail
Evan