johnr265

Okay, I've done my research and the car is going in for an alignment next week and I wanted opinions in regards to my conclusions.

Car is daily driven, and I want a good auto-x alignment as well. Track will likely come later when I am more familiar with the car. I am an experienced auto crosser but new to Porsches. Here are my proposed settings:

f Camber -1.6
Toe .04 toe IN per side

R Camber -2.4
Toe .25 toe in per side

Front bar 1 from stiff
Rear bar 2 from stiff

My rationale is, get some moderate camber that could support hoosiers for auto-x but keep a little front toe-in so the car is not too squirrelly on the street. Keep a decent amount of rear toe until I'm more familiar with the dynamics and then possibly reduce the rear toe if needed. Any thoughts or comments would be appreciated.

85Gold

I would max out the front - Camber without shims should be in the - 1.8 range.

Do not be afraid of 0 toe in the front.

Rear negative toe is a hair high, I would go .15 to .20
Rear negative Camber is spot on.

Sway bar settings depend on tire size and driving style. How easy do you want ot rotate the car in AutoX.

The SCCA 2008 SS Championship car ran front bar 1 off full stiff and rear full stiff. Hoosier A6's 245/35 front and 285/30 18 rear. The only other difference from the above settings is we ran ONLY .10 toe in on the rear. This is great for rotation but it is a little twitchy on the street

Peter

Rob in VA

+1 on the 0 toe up front. Lots of guys including me run .25 toe in on the rear...

I have very similar settings to your proposed settings and the car could use some more negative camber up front. Everything is a compromise and I do mostly track events. Maybe 1 or 2 autox events, but I'm not a very serious about autox, more just having fun.

calicoupe

great info! thanks

johnr265

How are those setups on the street? I currently have zero toe in front and it tends to not just find the grooves but will practically pull the steering wheel out of my hands, esp on hard acceleration. I thought a little toe in might give it more straight line stability.

Rob in VA

On the street the car is an ant eater. On the track the car is a blasty blast. Compromises.

NJ-GT

Peter,

I tested my car at 0.12 toe in at the rear (per side), and it really rotates. Indeed, it rotates too much. Definitely, this is the way one should run at the small tight courses at Nationals.

I went to a PCA AutoX on the West side, that thing was fast, almost 100 mph in one section (3rd gear close to redline on my car). For such high speeds, the rear was very sensitive. At the track it was a nightmare.

However, on the streets is quite comfortable, even on a Canyon run I did last Sunday.

Conclusion: If you are an experienced autocrosser, run 0.15 degrees toe-in at the rear and 0 toe at the front. The car will be fine on the streets. Do not go to the track with these settings, not even a soft rear sway bar fixes it.

Personally, I've been happy with 0.12 toe-out at the front and 0.25 toe-in at the rear.

Proof here:

http://www.stage6.com/user/GT3Rad/vi...Course-911-GT3

and here:

http://www.stage6.com/user/GT3Rad/vi...ss-Porsche-GT3

johnr265

Okay, so I'm a bit disappointed in how the car came back.

Front
R -1.2
L -1.4
Toe 0

Rear
R -2.7
L -2.6
Toe .2/.25

There seems to be a range of max front camber between -1.2 and -1.8 that folks are getting. Is this inter-car difference or is this due to the skills of the shop? Also, they were overly aggressive in the rear. They have offered to fix the rear gratis but said the front was maxed out.

I have also decided to do some DE this season so now my goal is acceptable for street, but good for track/autox. To get more camber in front, I understand my choices are shims or rotating strut bolts 60 degrees. My searching suggests that shims may cause tires to rub at full lock (likely only a problem in parking lots) and give more caster while rotating struts will give less caster.

So, given all this, should I:
a) take it to a different shop to see if they can get -1.8 without mods
b) do shims to get -2.5 (ala kussmaul). If so, what size shims should I get and who do I get them from?
c) rotate struts bolts and go for -2.5 or more camber

Two other questions
1) Are the kussmaul settings valid for street tires as well as R compound or do you really need the extra grip of sticky tires to start to utilize that much camber (for instance, I can tell I actually have LESS grip in the rear with -2.7 on winter tires than I did with the stock alignement).

2) If I do shims vs rotate struts, I assume that puts me out of the stock class in SCCA. Does anyone know which class they would be legal for (likely ASP or SM2). Also, if I do toe links or other minor suspension tweaks, which class would that put me in?

Thanks in advance. I want to get the basics sorted before the racing season really gets under way here. I really appreciate everyone's knowledgeable advice.

-John

NJ-GT

The rear toe should be equal, the 911 is very sensitive to differences on rear toe, it messes up the trust angle, the car doesn't drive well.

In your case, 0.05 degrees of toe difference between left and right is too much. You should get it equal or at most 0.01 degrees difference.

Your rear camber is fine. 0.03 degrees difference between sides is not noticeable. Obviously it is better to have it at the same measure.

You need 7mm of shims to get the front to -2.5 degrees, the tires will rub. You should be able to get more negative camber with the stock settings, somewhere around -1.6 to -1.8.

If you do shims or rotate the strut tops, you could be out of SS.

Wording on the GT3 WorkShop Manual:


"Note on front axle camber adjustment
Unlike the 911 Carrera (996), a basic camber
adjustment is made by means of two
intermediate plates on the 2-part control arm
of the front axle for the 911 GT3.
A 1 mm thick adjustment plate (arrow / Figure
78_99) is fitted as standard on the right and
left in the 911 GT3 MOO2 and MOO3.
By using thicker adjusting shims, the 2-part
control arms permit a correspondingly increased
camber value to be obtained for circuit use."

The three unused bores in the spring strut
mount are intended only for driving on racing
circuits. The three fastening bolts (M8) are fitted
in these holes in this case. This increases the
negative camber"


You would need to send a letter to the SCCA, so they can determine whether these two adjustments can be used in SS or not.

Anyway, you can safely use these two adjustments in ASP. The toe links will move you to SM2.

85Gold

NJGT is correct that you should be able get 1.7 to 1.8 degrees neg in the front without shims or rotating the struts.

If you are running SCCA SS then you CANNOT rotate the strut tops, ask me how I know, but you can run camber shims.

Peter

johnr265

Peter,

I'm curious, is there a reason you don't use shims then given they are legal? I was always under the impression with hoosiers that they really like as much camber as you can get. Thanks.

-John

85Gold

John,

I did tire temps and we were good @ -1.8 degrees. I am also ultra cautious with legality and I personally think the shims could be declared illegal if anybody did a protest, the reasoning would be for the same reasons strut rotation is illegal. Something must be right about my setup as Ian Stewart drove it to both the Pro Solo & Solo SS championships @ Topeka in 2007.

All that being said you need to set up your car for how you drive as there is no correct answer. The conventional wisdom 2 years ago was you had to run 245/315's to be competitive when we were running 245/285's. Now almost everybody in AutoX is running 245/285's. My car was also set up the stiffest, rear bar full stiff and front bar 1 off full stiff, while other GT3 pilots thought the car was way to loose with that setting. I will say , it sure rotates well set that way with .10 neg rear toe each side.

Peter

AllanJ

Hi Peter,

Were the temps taken after a regular run at a prior event or did you set up a g-circle?

Thanks,

85Gold

I took the temps at a T&T multiple times as we were also playing around with rear tire size 285 vs 315's . I know you are supposed to use a skid pad for AutoX tire temps but my theory is use a regular run as a skid pad is steady state which you never get in an AutoX where the car is constantly changing directions.

Peter

AllanJ

Thanks Peter. That's probably a reasonable theory. How close were your temps left/right? Last time I checked mine I was about 10*F from left side of the tire to the right side (inside a little bit hotter). I'm also about -1.8 to -1.9 degrees camber on the front.

Cheers,