Front Coil Springs for M030 Cars

[Spencan]

I have been looking around for stockish options of replacing my old original coil springs on my 1989 Turbo. I have found lots of information like this:

"The regular Turbo had a range of springs, depending on the tolerance group of the parts. These were marked by yellow dots (on the springs themselves). One yellow dot had the wimpier springs , while the "heavier" springs had three yellow dots. Two yellow dots fell somewhere in-between. These springs were 15.6 inches (396 mm) long uncompressed.

If it had the M030 suspension, however, then it had P/N 944.343.531.01, spring rate 28N/mm, inconstant wire diameter 11.7-12.2mm 12.9 inch (329 mm) progressively-wound springs. The lighter spring had a one white and one yellow dot, and the heavier spring had two white dots and one yellow dot.

Finally, the 1990 Turbo had springs P/N 951.343.531.03, spring rate 28N/mm, constant wire diameter 11.6mm, at about 14 inches (356 mm) in length. These constant springs went from one grey dot to three grey dots to designate the spring range.

Spring Rates (approximate):
944 normal stock rate 140 lbs
951 stock/M030 rate 150 lbs.
Turbo S rate 150-175 progressive rate
Cup car springs 375-410 progressive rate

If the spring rates are the same what performance difference does constant versus inconstant wire diameter make?

The constant wire diameter will be stiffer than a variable or inconstant wire diameter. Varying wire diameters are frequently used on progressive springs. The smaller diameter wire will compress first because it has a lighter rate. Once you pass that point, the thicker diameter coils should produce the same rate on either spring if you had them on a checker. Porsche doesn't usually stamp part #'s on their springs, rather they identify them with paint marks. If you look on the fiche, different spring part #'s will say, blue, purple, yellow etc. No spring rate info on the fiche unfortunately and Porsche, as mentioned above, measures rate in Newton meters."

I also found this part from Sunset Porsche: Coil Spring - Porsche (951-343-531-04-104) as a stock replacement, but from other sources but the other sources listed as non-M030.

So I could use anyone's help deciphering what options I have. TIA!

[Latitude48]

Spencer, if I were going to the trouble of replacing springs on a 1989 951 and I was using the stock Koni struts, I'd be inclined to do what I did with my S2, which was to fit 2.5" ID linear rate springs using a custom lower spring seat that threads onto the M030 collar, a jam nut, and upper seat, all from Racer's Edge. I've been running a set of Hyperco springs on this setup for close to 25 years now (wow, time flies!). I also have Racer's Edge camber plates.

The issue with progressive springs on the track is the handling can change once you compress the spring in a turn and hit the higher rate, making them trickier to drive, I think.

Cheers, Tom

Edit: here's pic of the front spring setup.

[Spencan]

Thanks so much for the practical advice! I have been searching and searching online trying to figure out a way to do just that. I spoke with Ian and Steve at 944 online and found out that the Porsche stock replacements were over $400 and in Germany right now. I did see somewhere about the change to the lower spring seat size.

What are the specifics of your setup (spring weight, etc.)? Any negatives/issues or things that you would change?

Thanks again

[SpeedMax]

Tom, what spring rate and length is that spring? Thanks

[Latitude48]

Tom, what spring rate and length is that spring? Thanks

I'm running 300 lb/in spring rate, and the spring length is 10 in, but could possibly be a bit shorter (especially if you go stiffer and can avoid coil bind) since there are plenty of threads on the collar. This rate is stiff enough for me on the street

[Spencan]

How many turns on your struts do you have it? All the way stiff, 3/4, 1/2?

[Spencan]

From Racer's Edge:
We would recommend you order two of the following seats at this link: https://racersedge-inc.com/lower-spring ... query=M030



And two hats at this link: https://racersedge-inc.com/upper-spring ... query=hats



Then order some springs at This link: https://hypercoilonline.com/hyper-coilo ... /2-25-i-d/

Stock M030 rate is approx. 170 Pounds per inch. Most street drivers that want a stiffer street spring go to about a 250 pound/in spring. You would need a 10” at this rate. This of course will increase understeer unless you do something to stiffen the rear as well.

[Latitude48]

How many turns on your struts do you have it? All the way stiff, 3/4, 1/2?

No idea. My struts are the double adjustable ones, which of course I never adjust

For the rear I have Koni 3012 coilovers with 275 lb/in 2-1/4" ID helper springs running in conjunction with my reindexed stock 24 mm torsion bars.

[Spencan]

Gotcha. At this point, I'm just trying to understand what I should buy for my current situation; single adjustable Koni Yellow Sports. Do I go with 300 lb or 250 lb and use the adjuster to dial it in?

Currently, I am on full stiffness with my worn springs. I only notice it when autocrossing. This last time, one of the corner workers noticed that my front was really diving and I actually had one of my rear wheels lift!

[chrischrischris]

I got a complete coilover kit from Ground Control for my car w/o torsion bars. They set me up with 450lbs in front and 650lbs in rear.