Holger B

That's exactly my setup and it works great on track without destroying the tires during street driving. NO shims needed. Just rotate (turn) the strut. That's what my guy did.

Holger B

That said, you still need a static setting. Mine's at 30' and it makes a big difference. IMO the rear toe is the GT3 suspension's Achilles' heel. The stock arm doesn't hold the setting very long, some will argue it changes under load and the car is a nightmare to drive when the setting is off. As a solution I got the Tarrett arm and the problem seems to be solved.

http://www.tarett.com/Browse_Item_De...ontrol_Arm_(pr)

Bob Rouleau

db_GT3 - You are correct in saying that rear toe-in is a compound adjustment. On the other hand it is designed to be adjusted. The settings often referred to as the Kussmaul indicate that. They got on this list of as a result of an email I sent to Alwyn Springer of Motor Sports who sent it on to Weissach. The result was an email from Roland Kussmaul with suggested alignment settings which I shared with this list. For a track driven car, more static toe in back is a good thing because the suspension will be more heavily loaded on a track with Cups (the alignment setting were specific to Cup tires) than on the street with N rated tires.

Regards,

Blacksport350

Okay, I am realigning to the Rolan Kussmaul settings on Monday and will hopefully banish my problems as this setup is known to work.

As many of you questioned what I use my car for...It is split between the track and the street with far more use on the street but is not a daily driver or trasnportation by any means...I have Euro seats, Cup harnesses and the rear cage.

I am not trying to set the car up for the street, I am trying to dial the alignment in so that the car "works" as it was intended with a skilled driver behind the wheel and I have driven GT3s that fit that bill. I have driven many more that are setup just like mine and handle badly. There is an art to setting up a GT3, or is it luck?!

Bob Rouleau

Blacksport - the Gt3 is very sensitive to alignment and ride height settings. That's part of its charm, the car is very adjustable. To get the required negative camber in front I suggest you follow Holger's suggestion of rotating the top of the struts. If you use shims on the lower A arm to get the required camber, you will increase the caster. On most cars this results in the tires rubbing on the fender liner.

NOTE: you do not have to go to the Kussmaul settings. If you drive the car on the street a lot you will wear out the inner edges of the tires. On the other hand if you track the car with a stock alignment you will wear out the shoulders.

Your 1.5 degree negative in front is a good compromise, as is neg 2 in back. If you track you car even once a month you will probably like the track settings.

You didn't comment on tire pressure. If you are running the factory pressures cold on the track your car will handle badly after a few laps. The hot pressure will be way up and the car will be unstable. See my note above please.

regards,

Blacksport350

The comment that I would have is that your toe should match left to right-your LR to RR is off .05. I would also want more negative camber in the front, either maxed out at 1.6 or rotate the strut top to get 2.5.

Phokaioglaukos

Thanks, Blacksport350. BTW, my sway bars are at OEM setting except one extra hole softer in the rear. I'm getting pretty even wear across the face of the front tires so I was not sure that the increased camber made sense. What would the effect of going to -2.5 degrees be?

Next year I'll probably try MPSCs, almost certainly if I get a second set of wheels, and try the Kussmaul settings.

What is SAI, Incuded Angle, Set Back and Thrust Angle, anyway?

Blacksport350

I do not speak from experience but I have talked to plenty of people with experience about this and it seems that on the GT3, -2.5* will not eat your tires unless you have too much toe. So with a total front toe of .08 or so, it should be fine. That is what I am probably going to try next. The increased negative camber should keep the front much better planted in corners by keeping your RA1s flat to the road or track as you corner hard.

Thrust angle is the relationship of the front to rear suspension assemblies. you want to make sure that they are set up paralell to each other. As an exaple, if for some reason the rear suspension was off in one direction or the other, it would actually steer the back end of the car and cause it to "dog track". Ever noticed those trucks on the highway that look like they aren't driving straight down the road? That is a thrust angle issue. Not sure about SAI or included angle.

With your bars, one hole softer in the rear will give you an extra bit of safety margin as the car will tend to understeer. This is also an argument for running more negative camber in the rear on a street car for this very reason.

Z06

I drive my car dailey.. 3.5 & 2.4.. toe fr .4 rear.9. even tire wear. If you do allot of hyway driving this could change the wear pattern.

The Toyo is a very tall tire.. your going far away from stock.. I think you should stick to the same diameters. The taller side walls make the car sloppy.

Larry Herman

No, it doesn't seeing as how 996/GT3s do not have kinematic rear toe links. Only the 993s do. The toe setting in a GT3 is quite simple and straightforward, and the links runs in parallel with the lower control arms to minimize any toe changes on suspension movement.

NJ-GT

What you have said.

Let me add that playing with ride heights, typically lowering the car, changes the angle of the rear toe link. This reduces the range of suspension travel before drastic toe changes.

By lowering the car, the rear toe settings under compression will create a toe-out condition (or less toe-in). Toe-out at the rear is exactly what we need to avoid.

If a street GT3 is to be lowered, adjustments to bump steer need to be made.

Phokaioglaukos

Here are the manufacturer diameters:

OEM Pirelli P Zero Rosso F: 25.4" R: 25.0"
RA1 F: 25.6" R: 25.6"

Not too much difference.

Z06

This is from the Toyo page... what sizes are you using?

225/40ZR18 25.1
275/35ZR18 25.6
335/30ZR18 25.9
245/40R18 25.6
305/35R18 26.30

Phokaioglaukos

I'm using the two RA1s that are 25.6" in diameter--245 front and 275 rear. The 335s and 305s rubbed on the fender lip under heavy suspension compression.

Blacksport350

How do you like it? With the setup, you lost 20mm of rear section width and gained 10mm in the front. I would be concerned that it would be tail happy unless you really altered your bar settings to compensate for the imbalance.

That being said, the car desn't really need the section width of a 295 in the rear for straight line traction and could use more in the front for braking.

Other opinions?