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Suspension - Anyone with experience with 500/350lb spring setup?

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Old 06-11-2009, 11:05 AM
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leonard928
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Default Suspension - Anyone with experience with 500/350lb spring setup?

Hey folks,

Can anyone tell me their experiences with the above spring setup. I beleive Carl from 928 Motorsport sells this combination as his Road/Sport setup.

Anyone have this? If so, please, what is your opinion of the combination?

I'm currently running 500lb Eibach coilovers on KONI shocks on the front with S4 springs on Konis on the rear.

Now thinking of replacing the standard rears for the 350lb coilovers.

TIA!
Old 06-11-2009, 01:34 PM
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Lizard928
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I would recommend spending the extra and getting the bilsteins.
600/400 is better IMO
Old 06-11-2009, 05:12 PM
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Okv
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https://rennlist.com/forums/928-foru...y-1991-gt.html

I would recommend replacing all springs front and rear, as the handling of the car may become very strange if spring rates front vs. rear does not match up.
The balance of the car may be seriously affected, it may get severe understeer or oversteer.
I also understand that the Eibach springs are progressive, and that will make it even more difficult to match.

I suspect the 500/350 set-up is a bit soft on the front, which will give the car more oversteer.
They are a lot stiffer than stock, but this is still not a very stiff suspension.
How soft, or comfortable it feels depends mostly on shock absorber settings.

If the springs you have are 500 ib linear, they may match up good with 350 rears, I would not go stiffer in the rear.
Old 06-11-2009, 09:54 PM
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Chuck Schreiber
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Leanord,
I've been thinking about this one for a loooonng time. First for the 79, then after I got the GTS after the driver side rear shock gave up the goat and lost all it's oil on the garage floor!!

I've been in the bilstein/eibach cars and they seem to handle good, but a bit bumpy. I've been in several old Devek setup cars that had the koni/hypercoil setup 600/400 and every one of them seemed solid as a rock, but NOT bone jarring. Looks like Carl is the only one that can reproduce this setup as you can order the springs in 50lb increments. Now the Devek setup offered externally adjustable koni's and unless I'm mistaken, DR is the only one who offers that flavor. (I think you can send internally adj to koni and they will make them externally adj) Someone correct me on all this if I"m wrong.

Doing my own research from folks that run the Devek (or similar setup) of 600/400 w the konis -I haven't spoken to one person that did not like it who ran it. Also, I've found it hard to find a post here on Rennlist on someone who complained about the setup. (Maybe a couple, but nothing that really stands out)

I originally wanted to go with the Bilstein/Eibach setup but I thought it was a bit "bumpy". That's just me though. It definatly was a great improvement over stock though!!!

Doing a search on the Bilstein/Eibach setup (There are TONS of posts on this setup) Seems that folks either love it or hate it and the debate rages on, regarding linear vs progressive rate springs.

Roger Tyson and many of the guys here in DFW land run the Eibach/Boge. Seems to be firm but comfortable.

I'm swaying toward the koni/hypercoil setup, but have a few more must do's on the car before hitting the suspension. I think the bottom line is, try to ride in someone elses car that has the setup you "think" you want. Everyone's taste is different and it's good that we have a few choices for our 928s!!

Good luck, let us know what you do!
Old 06-11-2009, 10:22 PM
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Ispeed
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Factory 928 springs are about 285/185 front to rear.

I have had 600/400 hypercoils for a while and am very happy. I however would counsel the average guy to try 500/350 as the 600/400 is a bit extreme for a street car. I have revalved Bilsteins to go with the springs. My friend George just did SITM (2000 miles round trip) on the same set-up as I have and had no complaints. After driving my car last year he insisted on doing the same set-up as mine.
There is no brake dive and no body roll with my set-up, but if you never flog the car on some twisties and haul some butt it will seem too stiff. When driving the car hard it feels perfect.

If I had to do it over again, I might go softer with 500/350 or even 450/325 or 400/300 or something. I am NOT NOT NOT NOT AT ALL a fan of progressive springs (the eibachs) because your shock valving is not progressive or speed sensitive and unless you do a revalve I think the Bilstein/Eibach set up sucks. As soon as you push past the soft rate on the spring, the rebound bounce is like a pogo stick.

I think just doing Bilsteins with stock springs is a good basic street set up, but for stiffer springs you need either adjustable Konis or revalved Bilsteins.
Both Bilsteins and Boge are made for stock springs and don't do well when you increase spring rates. The Bilstein do better than standard Boge in that case, but at 600/400 you NEED more dampening particularly rebound.

That's my opinion on a street car set up, I don't go to the track unless BRP counts...
Old 06-11-2009, 10:29 PM
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Chuck Schreiber
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Great feedback!
Ok, so how do you know just how much to re-valve the bilsteins? Do you send back to the factory and tell them what spring rates you have?
Old 06-11-2009, 10:55 PM
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Ispeed
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Chuck, it does not seem very scientific over there at Bilstein. Maybe it's just me, but the shock dyno graph they sent me is hard to make heads or tails of. I asked for 50% more rebound and 40% more low speed compression. My friend George's recently installed stuff we asked for 60% more rebound.

If I were sending them shocks now for the 600/400 I would ask for 30% more low speed compression and 60% more rebound. I am happy with my stuff.
Old 06-12-2009, 12:56 AM
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leonard928
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OK .. so far so good.

Firstly, my experience with the 500lb Eibachs coilovers on the Konis on the front of my GTS has been VERY positive. I don't believe these springs are progressive? For the kind of roads I'm experiencing down here in New South Wales, Australia I'm very happy with the front ends performance.

Sydney based Greg Gray, also a regular poster on this Forum, has the 600/400 setup and feels it is too hard for a road/sport setup.

Based on all your replies, I plan to go ahead and buy the 350lb Eibach coilovers for the rear. I'll also have the rear Konis wound up, as we did with the front set (then back them off a tad) and see how this works.

I believe this should give my GTS as close to the optimum I can expect with this combination. I'll let you know how it goes!

Thanks again for all your replies, much appreciated.
Old 06-12-2009, 01:49 AM
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justaguy
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I have hyper coils 400/250 from Carl with Bilstiens I find them better than the stock set up but a little softer than I would like. Feels good on the street but too soft for the track in my opinion



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