Jeff N.

OK - still very much a newbie here. Did some checking in the archives but wanted to get some first hand advice.

Car's a 86 951.

- PO installed Koni sport struts (non-adjustable perch in front) all around. Stock springs
- PO provided me Weltmeister 200lb springs

Here's my understanding of what I need to do to install these - comments?

- the Weltmeisters will lower the front by an 1 to 1 1/4
- they should work with my Koni struts
- if I want keep the stock ride height, I can with some spacers (I don't)
- I will need to adjust the rear ride height; this can be done via some adjustments in the rear trailing arms. General goal is to level the sill distance front and aft.

Re the suspension setup. Stiffer springs in front will generally increase understeer. I should be able to balance the setup by making some adjustments in the shock dampening (any suggestions on settings) to maintain balanced handeling. At some point, I might want to upgrade the rear torsion bar (but not today please). Sways are stock.

Car is going to be used for DE's, looking for a balanced to very slight understeer setup.

Comments?

Thanks in advance!

Jeff

2bridges

hey jeff - no way around upgrading torsion bars if you want car to be balanced.
with 200lb front spring - you would want a 26mm torsion bar for a slight push setup

your stock 86T is 23.5mm torsion bar - ideal for stock 126lb front spring

Chart on spring rates vs torsion bar size from Sway-a-way.
22m = 98.03 lb/in
23mm = 117.11
24mm = 138.84
25mm = 163.47
26mm = 191.24
27mm = 222.40
28mm = 257.22
29mm = 295.98
30mm = 338.97
31mm = 386.47

Jeff N.

Thanks - yes, that is my concern. I've read some posts that suggest you can balance out the car via adjusting the dampening. Trying to get the real world story on this.

2bridges

no damping or sway bar adjustment will propperly fix too small spring (torsion bar) in rear.

for street/daily use is not much of an issue. Will feel ok, just a bit soft in the ***..... at the track is where it will be evident.

turboted

I'm in the same boat as you...I'm installing my new suspension this weekend. I bought adjustable Koni's and upgraded to 200lb springs on the front...but I'm leaving the stock torsion bars in the rear. (I got adjustable perches for the front struts, so I can adjust ride height) Like you, I was concerned about how this setup would affect the car's balance, so I also bought a larger rear sway bar (19mm adjustable) in the hopes it will help dial out some understeer. I have no idea how well this setup will work...but I hope that the bigger rear sway bar combined with stiffer dampening on the rear shocks will create a fairly neutral balance. I'll find out soon...

PorscheDoc

This chart is for a car with rear coilovers as well, not stock shocks. For a 28mm torsion bar, you need to run about a 400lb front spring (i tried the 28mm with a 250lb spring, and stock rear shocks, and it was so far off it wasn't funny).

2bridges

?????
not funny doc.
Just installed my 325# fronts w M030 2.5" spring restrofit - and have my 29mm tosion bars here ready to go in.

I can't remeber where I got that chart, will have to go look.
I consulted with 5-6 individuals including a few racers and they all indicated 325 w 29mm setup would be well balanced

_________________________________________________________________
Hey Doc consider this - falls on chart about where expected

160lb front 25.5mm rear (stock 944T MO30)

PorscheDoc

If you search in the archives, there are a few posts that actually show the correct rates. There are A LOT of other posts showing that chart you posted above, but it is false information....according to my findings, because that is the chart I went off to start with. Big mistake.

2bridges

have searched tons...... after having talked directly to several sources, Jason @ paragon, local PCA racers in my area.

The consensous was a basic range:
200lb front 26mm rear
250lb front 27mm rear
300 28
350 29
400 30

chart above - more or less support all other info I have collected.


Did you setup on turbo car?
what sway bars?
Keep sharing Doc. Info appreciated and you can bet I will post up after my rear setup too.

Zuba951

So with the Front being 250 * .9 =225 and the rear 28mm 257 .....?

5speed300

I am running 250lb welt springs on the front and koni adjustables all the way around. Rear end is stock other than the koni's also. I just did a DE at VIR a few weekends ago so I can give you some pretty decent input.

The car does push a bit, but I was not driving it hard enough for it to ever become a problem ( was my first DE). I would like a more balanced setup however, because entering some of the medium speed corners it was pretty apparent the car was setup for understeer especially with teh setup I have on it now.

2bridges is right however, with a full tank of gas and stock torsion bars on the back... the rear end of the car feels really loose and soft. Coming out of corners at full throttle I felt like the rear end was squatting a huge amount, it did not feel nearly as stiff as the front. Its not dangerous by any means, just not as "comfortable" as I would like.

On another note, are you going to upgrade your balljoints with a geometry correcting kit? I have not done that yet but reading some posts on here was scaring me. I have completely new control arms up front and I was still worried the balljoint would fail with the lowered car and stock(albeit new) balljoints. No issues after my first DE, but the new joints have less than 1000 miles on them.

Im curious what you guys who track your cars with the welt lowering springs do about this issue?

turboted

I have 'heard' that you can maintain a neutral balance w/ front spring rates UP TO 225-250 lbs on stock torsion bars. Above 250 lbs, rear shocks/sways (even the adjustables) can no longer keep up with the front end stiffness.

Did I dream this?? (<-- maybe!)

2bridges

no shock can increase rear spring rate.
single adjustable konis will adjust rebound. nice, but has no impact on spring rate.

I do know some who use adjustable rear sway bar to "preload" and simulate more rear spring rate. Definately not the best approach in my book, but some like it.

PorscheDoc

That looks more like the correct chart. Looks like 350 should be about right for you. After look at my records, I put in the 350's (its been awhile), so I was high on the 400. All installed on an 86 turbo. Planning on installing M030 968's here in the near future, but not sure how that will affect things. Stupid long term projects, lol

2bridges

I am running koni m030 single adjustable, and setting up with 968 mo30 30mm front sway bar and 22mm welt adjustable rear sway. Can't wait!