MAGK944

About to pull the trigger on the Ground Control front & rear coil-overs (torsion bars deleted).

This is for the road car so a little bit of understeer would be good. I have the MO30 30/19 sways and am planning on 250# fronts 425# rears for the coil-over spring rates. This makes an effective 240# at the rear. I will have some 'tweeking' adjustment with the rear sway bar, tire choice and height settings. So just checking for any stupid errors in my calcs before I buy.

V2Rocket

how does a 425# spring turn into a 240# spring?

MAGK944

Because of how it is mounted on the rear suspension. A 425# coil spring has an effective rate of 240# on the Porsche 944.

alex

cause of the torsion delete-

tifosiman

The effective spring rate of the spring would change regardless of the torsion delete. It has nothing to do with that.

Lemming

I run coil overs all around on my trackcar (torsion bars deleted). My first set of springs were 400 front and 450 rear and that set up was completely neutral . Based on that I would think that your 250/425 would lead to oversteer.

Also running M030 bars on my track car (rear set to middle), but I'm guessing that I run a bit more negative camber (-3.5F/-2.25R) that will also affect under/oversteer.

ucrackaass

off topic, but how did you install that front 30 mm. i just finished installing this setup in my car and the sway bars making a thud noise in the front, im gonna take it back into my automotive class and take a look at it as well as check the alignment b/c i install new poly lower control arm bushings aswell.

but how did you install it? i had to hone out the bushings that were there already b/c the guy at paragon told me the bushings that it was meant for would not fit my control arms. i have an 87 924S.

did you have to do it like this too?

MAGK944

They fit fine, I got the complete M030 kit with all the correct busings. You need the end bushings also + the circlips for the ends. I think on the 924S you might need larger suspension clips too.

MAGK944

Confused here, glad I asked the question to clear this up b4 I order.

The 425# rears have an effective rate of 240#, so I will be running 250F/240R which should give me neutral to mild understeer (all else being equal).

Your set-up with 450 rears (effective rate 253), would give you 400F/253R and huge amounts of understeer. You need to move to an 800# rear spring to get to 400F/450R and a neutral balance.

It's a learning process for me, so please tell me if I am completely wrong.

shiners780

Don't forget the front effective rate is approximately 90% of actual.

I would think your chosen rates are a good place to start. Rear springs are easy to replace, and pretty cheap too. The shock valving should allow for a fair amount of spring rate variance.

Also, what feels neutral to one person may feel pushy or loose to others. There is no way to know without experimenting.

Lemming

I would not have thought that 400/450 would be a good setup, but I took the advice of John (Redlineman) and was extremely happy with the setup. I now run 600 lb springs all around and it is fantastic.

MAGK944

Perfect Jim! I wasn't sure of the multiplier for the front springs and now I know.

So 250F/425R springs would give me 225F/240R effective rates. Therefore I might go more neutral by dropping my initial rear spring rate slightly, say to 400#. That would give me 225F/225R effective

JM3

Instead of dropping the rear rate, you should go up on the front rate.
250 is REALLY soft.

I know that 250 sounds high, compared to the stock number, but if you stop and think that whenever a shorter 250 is used on a -standard length- strut, that the car is the bumpstop very often, so the actual rate you feel is HIGHER than 250.


JM

white924s

I think that the ground control coilovers have custom springs, so shorter springs shouldn't be an issue

also, I think he said its a street car, so it may be easier to start soft and work up in spring rates rather than going too stiff and suffering until you can get softer springs.

slightly off-topic, but I've actually been looking into those coilovers a bit online (read: staring at GC's website and drooling) and I would be very interested in hearing any feedback you might have on the system when you get it on the car

roman944

hey gina, is this for that early car? or do you have another?
because you are doing pretty much what I had in mind, so this is very interestign to me and is getting bookmarked!