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jazz guy · Joined: 26 Nov 2002 Posts: 434 Location: Colorado

Hey Guys,
I am going through the '82 931 suspension and want to share my proposed setup to get some feedback. I've done quite a bit of research and come up with a number of different opinions. I have many of the parts on the car now or in my possession but haven't sprung for the front springs yet, pardon the bad pun. I'm also not sure if my fr. sway is large enough.
The car is not a daily driver, though I drive it regularly. It will see about 80% street time with DE/AX/Club Events filling out the drive time. I'd like fairly balanced handling, front and rear, with slight initial understeer. Need enough oversteer to rotate. I love how these cars will take a set and don't want to lose that and end up with a twitchy setup that is no fun or not safe on the road. Here is what I have going on:
-Wheels: 7 fr./ 8 rr. 16 in. - Tires: 205-55 fr./ 225-50 rr.
-Bilstein HD's fr. & rr.
-27mm torsion bars
-18mm rear sway ('86 951)
-Paragon coilover conversion w/ #225 or #250 springs
-22.5mm front sway ('86 951)
-new bushings - pretty much everywhere
-Ride height - 1in. lower - rear height level with front

All comments/suggestions/help greatly appreciated!

Cheers, Brian

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

I'm no expert in these matters, but just looking at the stock setups, I think with 18mm rear sway, I'd be looking to run the larger 24mm front sway bar that was matched on the 86 951 M030 option, especially with the staggered wheel widths. I might even have a 24mm bar available for cheap.
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jazz guy · Joined: 26 Nov 2002 Posts: 434 Location: Colorado

Thanks Dan, I am looking for any ideas. Am I correct in thinking that the 24mm M030 bar is hollow. If so does it have a higher effective rate than the 22.5 solid bar, or is it just lighter?

I know that suspension setup is a blend of science and mystic art, so it is hard to give absolute answers. Additionally, each driver has different preferences. But what is puzzling me is the wide range of opinions. We have some knowledgeable board members running uprated front springs/ARB's with stock torsion bars/ARB's liking the setup; yet in talking to several places, springs up to 350lb. springs have been recommended with my 27mm torsions. Paragon suggested 250-300.

According to the Technical FAQ, 944 turbo S models used 25.5mm torsions with 160lb front springs. That seems like pretty stiff torsions with no increase in the front spring rate compared to what I'm hearing. ???

I don't mind doing some tweaking and experimenting but if I really do need 300-350lb front springs to balance out the 27mm torsions, then I need to rethink this. I want to keep the fillings IN my teeth. Thoughts...

flosho · Posted: Fri Oct 16, 2009 2:22 am Post subject:

You'll want to see how the car will react.

You are running offset wheels which will produce some understeer tendencies. You could stick with the 22f/18r to try to keep the car neutral and see how it reacts. If the rear end is sliding around upgrade the front bar.

I have a 19mm on the back of mine, and the stock bar on the front, BUT I am on 255's in the rear and 205s in the front, and just springs in the front. I have a feeling when I switch to r-compounds on 16's with 205/225 setup I may have a drift machine, but as it sits right now its pretty balanced.

Also, don't forget about alignment settings.. You can do some searching but from what I remember...
front:
-2 degrees camber
1/8" toe out

on the rear:
-3 degrees camber
zero toe or (slight toe in?)
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jazz guy · Joined: 26 Nov 2002 Posts: 434 Location: Colorado

Thanks for the input Flosho, I definitely will be getting a good alignment.

Your thoughts on the bars makes sense. Btw, what spring/torsion bar rates are you running?

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

According to the Pasha article:
FRONT SPRING || FRONT SWAY || TORSION || REAR SWAY
86 951 (M030 opt) 3250N 24mm tubular 25.5mm 18mm

87 951 (M030 opt) ??? 25.5mm tubular 26.8mm tubular 16mm

So you have a point about the 22.5 solid vs. 24mm tubular. I would expect them to be roughly equivalent in terms of torsional resistance...
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flosho · Posted: Fri Oct 16, 2009 7:39 am Post subject:

Vince Ponz · Joined: 02 Nov 2002 Posts: 3581 Location: Florida

I am running a 25 1/2 mm front sway with adjustable rear sways. Runs fine. HD shocks with 7s and 8s euro tranny etc.
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gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

924RACR · Posted: Fri Oct 16, 2009 9:43 pm Post subject:

I'm with gegge...
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'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

jazz guy · Joined: 26 Nov 2002 Posts: 434 Location: Colorado

Thanks for the replies! After reading your thoughts, doing more internet research (I've done extensive searching and reading on Pelican, Rennlist, and here, of course) and info gathering from How to Make Your Car Handle (an oldie but goodie) and the guys at Paragon; I am pretty sure that I need at least 250# fr. springs with a larger fr. arb for my car. The setup could probably benefit from springs up to 300# and that is where I start to get a little weak in the knees. That sounds pretty stiff for the street.

I know Vince and Chrenan (now Slam's car) have positive results with 250# springs and healthy arb's; in case I need go bigger, does anyone have experience with springs in 250-300# range on the street? And, as gegge brought up, will my Bilsteins handle springs up to 300#? I want to significantly improve handling and don't mind an aggresive sport feel but as I said earlier, I do want to my fillings to stay IN my teeth.

I've been waffling back and forth about this so much that I'm starting to sound like Brett Favre. And even Brett in his Sears commercial said, "I hate those guys," (who can't make up their mind)... I agree... I'm dropping the hammer on this by the end of the weekend.

Last comments anyone? I promise to make up my mind...really

flosho · Posted: Sat Oct 17, 2009 2:05 am Post subject:

I don't mind 250# 1" lowering springs on the street.

When I upgrade, I'm gonna go ~400-500#
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Shurick · Joined: 15 May 2005 Posts: 524 Location: Russia, Moscow.

I don't want to hijack the thread, but I'm also thinking about suspension setup. Which springs and t-bars should I prefer with yellow Koni Sports?
I'm looking at #250 springs at front and 27 mm t-bars at rear. The anti-roll bars are 23 and 14 mm. Wouldn't it be too stiff for my dampers?
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'79 931 -- intercooled K26-3060-6.10 turbo @ 1.2 bar, EFI+EDIS, 951S brakes, stripped interior, 951 look.
'86 924S -- R.I.P.
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924RACR · Posted: Sun Oct 18, 2009 10:32 pm Post subject:

Konis can handle up to about 350# springs and t-bars to match... they start to break down once you get up to 400#/30mm setup... basically they can handle it, but wore out early on track, I found.

I haven't run the Bilstein HD's with such a setup; have 'em on my 931, but that's stock. The racecar rolls on Bilsteins, but they're custom race units.
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Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

john h · Posted: Mon Oct 19, 2009 9:39 am Post subject:

For ride height I'd recommend lowering the back slightly more than the front so you have a slight rack backwards.
I've found in racing even with #250 springs at front if you have the car level under heavy braking you can get weight transfer and hence the rear wheels start to lock up (especially mor enoticeable in the wet)

Also with the change in wheel offsets I'd recommend the brake circuits be split to both front on one circuit and the rears on another.
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