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Hey guys, I need some help here. I read from this forum about a nice handling improvement for the 996 GT3 by re-valving the shocks and pair them with 500lb Eibach springs front (7") and 700 lb springs rear (8"). Also dropping the height by .75". Do any of you have experience with this setup and any comments?
The current setup is as followed. I already have real toe link upgrade. Comparing to my old 1999 996 with track setup, the GT3 is still feel twitchy though I am getting more used to it (I bought the car around June this year)Front axle:
Camber: -2.5º
Max camber difference, left/right: 5'
Toe total: +5'
Toe difference at 20° lock: -1°20' +/- 30'
Caster: 8° +/- 30'
Max caster difference, left/right: 30'
Front height: 115mm
Swaybar – 1 from hard
Rear axle:
Toe total: 35’ +/- 2'
Max toe difference, left/right: 5'
Camber: -2.3° +/- 5'
Max camber difference, left/right: 10'
Rear height: 128mm
Swaybar – 1 from hard
By the way, I am a PCA DE instructor (for about 10 years) and club racer (SPB about 8 years). I know I should take it out as is and face the challenge. But it does not hurt to get more out of it.
Also, I would like to know the spring diameters so I can order these Eibach springs.
What a timely thread...This past summer I went from a 2003 C2 that had some suspension setup to a 2004 GT3...actually in June the same month as you. Anyhow you are probably a better driver than me but I agree the GT3 feels unstable on the track compared to my C2 and I am actually slower in it around my home track.
The GT3 I bought was setup to Kussmaul settings, with which (IMO) it drove terribly. It sounds like yours is setup about the same. The somewhat old A048 tires didn't help either. Took it to the track "as-is" (aside from moving my roll bar, seats, and harnesses over from the C2) one week after I bought it and spun the car more than once that day, driving it similar to how I drove my C2 there...had to back it down a few notches.
So then I had it re-setup by a local speed shop I use with roughly what I had on my C2: Camber at -3 front and -2.5 rear, zero toe front and slight toe-in rear. Sway bars full soft in the rear and one off full hard in the front. Ride height at basically Cup car height then corner balanced which did bring the front up a little, but not much.
The car drives light years better setup like this but I now feel like the car is under-sprung and has a harder time maintaining grip in the corners than I think it should. As you probably know the stock springs are pretty soft 228 front and 550 rear (but of course compression and rebound are important too beyond just the springs).
So my next step is new coilovers this winter. Leaning towards JRZ's right now. FWIW there is a guy on the forum selling a set of stock GT3 coilovers revalved with larger Eibach springs, you can find them in the classifieds, AFAIK they are still available. I have decided to go with adjustable instead, with some pro setup help.
That's my journey so far, not sure if it helps but that's been my "experience" so far.
make the jump to Ohlins or similar(IMHO the value isn't there for springs/hardware +revalve stock), solid rear thrust arm bushings + monoball inner LCA and align it right
people get too caught up with spring rates (very application specific) , the dampening is what matters... good dampers make the suspension
make the jump to Ohlins or similar(IMHO the value isn't there for springs/hardware +revalve stock), solid rear thrust arm bushings + monoball inner LCA and align it right
people get too caught up with spring rates (very application specific) , the dampening is what matters... good dampers make the suspension
Absolutely agree that spring rates can only be selected for overall performance and not specific to any given track. I have Moton 3 way suspension that has been rock solid from day one and provides plenty of adjustability. I have two sets of rear springs and change them depending on the the track. The more technical the track, the more you want to put the power down and the softer you want the rear. Otherwise you're spending a lot of time gathering it up on throttle exiting corners. I'm not sure if Moton Motorsport 3-way is still available.
Racer 951 - What tires are you running???, it's going to make a difference on where some of the settings need to be.
The one thing that sticks out, as Nick also pointed out, you have too much rear bar in the car. Depending on the track I run either full soft or 1 from full soft. That's going to calm down the car quite a bit and make it much more comfortable for you. This is the first thing I'd do then drive again and evaluate more.
Re-valved and re-spring Bilsteins are OK in my book, they fix the spring rate issue but don't really get you much beyond that. In that spend range I'd look at the Ohlins but even they aren't a perfect solution as I feel they need more front spring rate to really be "good" for track duty... still a much better damper than the OEM setup.
OP: I think your alignment settings are fine except the rear bar as Andy mentioned. You should try full soft or close to it. Your spring rates are very low for the car if you are running stock. I switched to 700/900 years ago and the car has been a pleasure to drive.
A couple things I'll add to the driving style for an older GT3:
1) 6GT3 trail brakes and accelerates very differently from the SPB (and even a standard C2). In my SPB, things happen in a "twitchy" kinda way. The car trail brakes in little squirts that you have to control with a quick cadence. The GT3 has the engine at the rear and trail braking happens in longer sweeping motions. To me, it's actually much easier to trail brake the GT3. You really need to trail brake deep to be fast. You can find 2 or more tenths a corner trail braking [most tracks you'll see ~2 seconds a lap with better trail braking].
2) on corner exit, there isn't really a progressive throttle in these old mechanical cars. If you try to roll onto the gas, you are leaving free time on the table [a tenth a corner = more than a second a lap]. You almost need to treat the throttle as a 2 way switch. You transition from brake to 1/2 throttle, and if it sticks, immediately to full throttle. The 1/2 throttle puts weight on the rear and sets the car. Once set, it'll take all the gas you can give it. You might need a hair of countersteer somewhere, but eventually) get to full throttle.
When I switched from a C2 to a GT3, I was running identical lap times because I was driving the GT3 like a C2. But after some pro coaching, improving just those 2 things netted many seconds a lap.
On a separate note, at it's best, the SPB is only ~3 seconds slower than the GT3 - with 1/2 the HP. On average (with me driving) it's 4-5 seconds slower.
That's the exact thread I used as a reference for my alignment setup. I setup to AudiOn19s' settings but I don't have the JRZ's that he has, stock coilovers still for me.
Hey guys, I didn’t check this thread for a couple of days. Thanks for all your great feedback and comments! To answer the question about tires, the stock wheels have new Sumi HTR Z 3 and Fikse track wheels have an old set of Michelin PS2. Since I bought this car 4 months ago, I haven’t taken it to the track yet. I have no idea how the old PS2 will hold up.
i mentioned I’ve been racing SPB for 8 years. But I recently crashed it at Laguna Seca right after I had the PSS 9 rebuilt, corner balanced and re-aligned. The day that I crashed, my SPB felt extremely twitchy. I guess my previous setup was ok for worn shocks but with newly rebuilt shocks, the car felt totally different. Long story short, with this recent crash, I’m a bit nervous about tracking a twitchy car like the GT3 especially it costs more than 2x of my SPB. I like the idea of softening the rear sway bar. I have to do the same with SPB, some racer even disconnect the rear sway entirely.
“Himself”, sounds like you and I have 2 things in common: 04 GT3 and SPB . Thanks for sharing your experience. I assume you had the bilstein struts re-valved to match the 700/900. With these spring rates, how does it feel for street driving? I still want mine to be streetable. Also, did you send the struts directly to Bilstein and where did you order your springs? H&R or Eibach? Diameters, length etc. these info will be helpful. Also, ride height?
Speaking of trail braking, my daily driver BMW 228i M Sport trail brakes surprisingly nicer than the SPB. Much early to dial it in. As for the throttling with off/half/on switch mode driving coming out of a turn, I guess that’s generally our SPB driving style . I did the same with my old C2 with LSD. It works great. I had to tell my students to just stay on the gas even when you drop two wheels off the exit berm, especially if you have LSD. I can’t wait to test my GT3. I guess I’ll just soften up the rear sway first and see how it feels before spending money on it.
PCA doesn't run my home track, so I have been running SCCA in E-production. I'm going to make my first PCA race at MSR-Cresson (Maverick Region) next month. The other close tracks that we run are COTA, NOLA (Louisiana) and Hallet (Oklahoma). Circuit of the Americas is a cool venue!
himself, I just called Bilstein regarding the re-valving of the struts. They said they cannot simply re-valve the struts and try to match the spring rate. What they normally do is to re-valve it based on the percentage increase on compression and damping specified by the customers. How did you have your struts re-valved to match the 700/900 spring rates?
Glen Lee can rebuild stockers as you wish, i went that path as i drive around chicago still. Dont forget to completly evaluate all rubber bushes before making a change, perished rubber will have huge effect on everything.
Theres a bunch of other stuff but ill leave that for experts like andy.
10-22-2018, 08:59 PM
996 GT3 Suspension Improvements
. Thanks for sharing your experience. I assume you had the bilstein struts re-valved to match the 700/900. With these spring rates, how does it feel for street driving? I still want mine to be streetable. Also, did you send the struts directly to Bilstein and where did you order your springs? H&R or Eibach? Diameters, length etc. these info will be helpful. Also, ride height?
