OK, so I decided to take a few hours off from the pundits at Rennlist
And in the meantime call a couple of highly regarded race shops.

The summary of what came out of those conversations are as follows:

1. The rear toe definitely makes a big difference, and the consensus seems to be minimum 4mm total, but even up to 5mm was suggested. This is in agreement with what's been said on this thread.

2. These cars really like more camber in the rear than the front. So if front is at -2.0, the rear should be at minimum -2.2 if not up to -2.5. Although the latter might start to chew up the tires on the street. This is not in agreement with this thread and the thread about the GT2 rear sway bar. Weird.

3. It didn't seem that the GT2 sway bar was deemed necessary, and the stock one should be able to do the trick. But it wasn't disparaged either. It was more a suggestion to start with stock and develop from there.

4. PASM shouldn't have much bearing on what we are talking about, and should be fine for what I want.

5. It's the tires, stupid. Inadvertently, I have wound up with mismatched fronts and rears in several turns. Front heat cycled/aged out with fresh rears. Then fresh fronts with 60% worn rears. Add to that, as has been pointed out that N-spec cups suck. Will probably try R888's now.

6. Ride height was mixed. Some suggesting that with this car I wouldn't be able to tell the difference if it was on high or low setting, and others saying lower always helps. But it didn't seem like a really big point with either. What was said was that USA delivered GT3's come with fairly random ride heights....

Essentially for what I want, which is not necessarily the fastest setup, but a good track set-up that is also streetable, and more importantly feels stable and confidence inspiring, it seems that the suggestions were: get matched tires first of all, then do a set up that is actually not that far from what it says in the manual..... Go figure.

BTW, In looking back at my notes, I see that my rear toe initially was even worse than I described. It was only .1 deg. each side which is less than 1mm. I.e. I had less than 2mm total toe-in for the rear. That was later corrected to the 1.77mm each side, which is still not enough.

The only thing that puzzles me in all this, is the big disparity in preferred rear camber. It seems that most here prefers the less camber in rear set-up, whereas the race shops unanimously prefers more rear camber than front, which is in agreement with the manual.

I'm now leaning towards starting over with fresh (and matching) tires, a basic RTFM set-up, and see how it feels. Then adjust gradually from there. That may eventually take me to the less rear camber that seems preferred here, but at least I'll do that with tires that match and correct toe.

Thank you all!

-Christian

 

it's really pref. but here is mine. i have extensive trk miles on 6gt3, 7.1 7.2 gt3/rs


rear toe, i agree with your finding. however, if you think your 7 isn't dancing as well as 6, reduce rear toe it WILL dance.

i never found GT2 rear sway did much. well. i dont do much adj with any sway bars. those adj are very fine tuning. but i find the oppsoite that "I" needed a lot more camber up front then rear and most of the drivers do run more camber up front, some by as much as 1 deg more negative front than rear.

PASM is fine.

if you are not running brand new tires, you are just chasing your tail. pick one type and one size of tire, align to those and drive drive drive. then you have baseline to move from. always new tires. used tires or even 50% old tires will not give u right feel, until you know them well.

R888, imho, is not the tire you want to start with to learn the car. i would try trofeo, mpsc and such or NT01

ride ht had very minimal affect for me.

good luck in your experiment. the 7 will always be more numb than 6.

it appears u are driving 'fake' mpsc? you need the real mpsc.

 

Thank you for your insights!

The rear camber settings definitely seems to be an area of disagreement, so I'll have to try it both ways. I wonder if you or someone else could elaborate on why less camber in rear is better? Is it faster/rotates better but maybe less stable, or is it actually more stable? I.e. what is driving the preference? (Strictly no pun intended.)

For the R- comps for this car widths rock 19's, it seems that the real MPSC's and NT01's don't come in the right size or with the right outer diameter. It seems the choice is between R888's, Trofeo's, and MPSC N-spec. From I can read, the N-spec would have the least grip, and the Trofeo's would wear out the quickest, which is why I thought R888's. (R6's can't be driven on street, so not looking at those.) Could you elaborate on why not the R888's? If I'm used to the real more grippy MPSC's and how long they last, and their semi-decent streetability, what would you suggest for this car? BTW, I'm not interested in going 18's. At least not yet.

Thanks,
-Christian

 

7.2 is a little too stable vs. 6
as such, less camber in the back makes it turn better, less rear grip. but with the toe "in", you can still put power down exit corners. i also set the rear full stiff or one from full stiff. (but i also run more less rear camber in the 6, i run less rear camber in all my cars... and i still find them pushing but i like a pushy car.)

i run 18" so dont have much knowledge on 19" sizing.
but i do know trofeo R comes in 19" and are loved by many.

R888 has no grip to me. wears out fast. inconsistent from beginning to end of a session. i have tried different pressure from 30psi all the way to 42psi. nothign works. we changed alignment every which way, no working. but that's me driving. you might find the ok. i hate R888 to the point that i rather just buy the cheapest rock from costco instead of R888.

 

I run my car with slightly more camber in the rear.

However, that is on race spec MPSC front and N-spec MPSC rear. And on my old shocks, which were dead.

Now have new shocks and Trofeo. Car push's so will need to step up front camber.

 

The 7.2 is VERY stable if you drive 7/10th like me, limited by "skill, fear, wife and insurance" (I love that quote by "mikymu" ;-) AND a camber-setting of -1.9F/-2.0R. That's all my mechanic was able to get (in the front) without messing around with rotating strut, shims etc. I wondered at first what that would feel like (more rear camber than front) but soon found out that the rear sticks like crazy BUT the front pushes like h...l to the point where my front tires were nearly worn faster than my rear, unheard of for a 911. But than again, some of that front wear is due to my driving style, "fast in, slow out"...

My REAR tires (N-MPSC's) after 12 track days (about 100min each), driving to/from the track (175miles), are evenly worn to the wear bars now. I would like a better turn-in and earlier power-on ability but until I decide to increase front camber, I'll accept the "pushy" car with a stable rear. I just can't stomach (yet?) a twitchy rear at 90mph+ (love tight corners, though:-).

I also love my OEM MPSC's (3rd set now), given that I don't know any other tire. They're (very expensive), very predictable and consistent throughout their lifespan with the only challenge of getting them (and keeping) the right pressure which for me is 33F/36R. My car is all stock, except the camber. And I leave all the nannies on. I paid for them so why not use them

 

Christain,

Trust me the alignment and the new tires.
Slightly more camber in the front than the rear and the car will be neutral - not scary. I'm #3.

 

More camber in front than rear most definitly.

 

Interesting. Just spoke to my friend who drives a Boxter Spyder, and he said the same thing. Hates them. Says there is too much tread squirm, they're greasy feeling, and he also tried all different tire pressures and alignments.

I really wish the original sticky MPSC's were available in the proper size for this car.

Can you elaborate on why you say the 997 will always feel more numb than the 996? This is a really, really important point for me.

Thanks,
-Christian

 

Were they shaved or full tread? R888 are terrible at full tread in the dry.

 

i also raced a spec boxster on R888.
i ran R888 on 6gt3 as well.
no matter what cars i put on, they are garbage for ME.

i dont know WHY 7 is numb vs. 6.
maybe b/c it's stiffer? maybe different suspension geometry.
but it just is.
if u drive 6 back to back with a 7, you see that right away.

 

shaved to 3/32.
driving it full tread... you might as well just not drive at all. yes, i REALLY hate R888.