outline

can i ask where you got your figures from for the alignment settings?

gt3 street specs are as follows:

Rear Axle:
Camber: -1.50 degrees +/- .10 degrees
Toe: +08' +/- 05' Total Toe: +16' +/- 10' axle angle: 0' +/- 10'

Front Axle:
Caster: +8 degrees +/- 3 degrees
Camber: -1 Degree +/- .10 degrees
Toe: +03' +/- 03' Total Toe: +05' +/1 05'

this would have been the place to have started and then taken it from there depending on how you felt the car perform. making adjustments to setup from a known benchmark are always the best process.

AudiOn19s

Kussmaul settings are pretty much a benchmark baseline for the GT3 guys as far as agressive allignments go. Dan's pretty close to those settings currently.

mglobe

My point on 245/285 isn't so much about the overall tire size as it is the ratio front to rear. With the -2.5/-2 camber he's running, I would not expect to have that much push. Granted the roll bars are probably not right, but I'm guessing (emphasis on the guess part, still learning this stuff) that the setup is overpowering the front tires. Going 245/285, or maybe dropping the rear tires to 275 might help balance the car some.

Paul 996

There should be no toe in on the front.. Toe should be zero (pretty sure I mentioned this in my pms). This is your biggest source of understeer. The only situation that you would want to go the other way and have toe out at the front would be in an autocross car setup. I still swear by zero toe at the front.

Also, the C2 stock roll bars don't help things at all. The adjustable drop links that you bought are now the wrong length in the front to use with the GT3 roll bars that you need to upgrade to next.

Fissionx

I'm really unhappy with the car now. I am taking the car in tomorrow to adjust the alignment (0 toe front and less camber front and rear a bit). The car is unpredictable on entry, and as hard as I try, I feel like I can't be smooth with it. The car just does whatever it feels like on exit too.
I knew the 911 was going to be much more challenging to drive than the M3, but damn.
Also, I have this god awful crap box exhaust that is so damn obnoxiously loud. I still can't find some used OEM muffler cans. Oh yeah the tires suck too. AND I was pushed into an insulated light pole karting tonight and my chest and neck ache bad. Tomorrow is going to hurt.
/vent

trackjunky

Fissionx, something is off here.

1) are the shocks new or did you buy them used? If used, you could have a dead shock.
2) The GT3 sways are designed to go with the GT3 shock set up, so you need the bars.
3) Sping rates. Sounds stupid, but did they F-up and put the wrong springs up front? Sillier things have happened to me. I noticed your post where you talked about 993 springs? sounds fishy. Start there.
4) Shock settings. Too stiff up front/too soft in rear will cause a push. (Same for sway bars.)
5) your alignment is not way off, but it could be better. 1 degree up front and 2 degrees out back for a compromise car. zero to slight toe in up front with some toe in out back. Remember, these cars toe out in the rear when they squat under acceleration.

Just some ideas. I usually think opposite end 1st on changes (carry over from my karting days) but I'd need to know more.

Pushing on corner entry under braking? Under throttle? How about mid phase and corner exit? Is the car darty or does it feel stable in a straight line?

Fissionx

1) used with 4k miles on them. It could, and that's what I thought at first, since the problem was much more noticible at low speeds, in turns with fast weight transfer. I don't know if it could also be poor valving from the factory, but the OEM gt3 I drove back to back with my car, felt more like my car than the ROW M030 I drove.
2) yeah i know, those are next
3) rear springs are right, the front 993.xxx spring is OEM, put on the gt3s in 2005. No one really knows why. Maybe the 996 spring was too stiff, or they ran out.
4) shocks not adjustable
5) Yeah, the difference in grip is huge when the car takes a set on exit, and feels like the rear 'steers' more, which I assume is toe change, not just weight change. But, I feel like this transition takes a while (too long) after i apply power, and it's not smooth.

Ok so all this is from my experiences on street, so take it with a grain of salt.
Car feels okay with trail breaking (ie has grip). Initially on throttle, the front end pushes a lot, i have to open up the wheel excessively to get it to bite. Car feels a bit darty, it has a lot of camber, but also toed out, which should help I guess.
I'm hitting the bed now, post more tomorrow after alignment change.

Do you have problems with bump steer in the front? When I had the car on the lift for alignment, the front toe links look like they had a 10-15degs upward angle. I have read the GT3 carriers use a lower mounting point. The car (GT3 height) is much lower than it was designed by porsche.

trackjunky

You should really use GT3 street control arms to go lower. Don't go too low on a Carrera, the suspension is not set up for it. **** binds and hits things -- bad.

If your car is understeering that bad at street speeds, something is wayyyy wrong. I'd definitely suspect a shock or spring issue. Look there first.

The darty feeling is from toe out up front. I don't like this. Zero toe is plenty darty for me. I like about zero to .03 toe in up front on each wheel. That is on a Hunter 4000 alignment machine. Rear is about .05 now, but we'll see what happens. I like the car to be "lively" at the track and change positions quickly, but this really makes the car a handfull on the street. You need to be on top of it, especially with the camber changes.

Do you have aftermarket drop links? If so, make sure you did not dial in any "pre-load" to the drop links. In other words. set the drop links with the car level on the ground and they should each be movable with your hand. If they are bound --- fix it. I also like 1 degree greater camber up front than out back as a general rule. So -2.0 up front and -1.0 in back, and so on.

PM me with any other questions.

Sleep tight.

LVDell

Bill, I have to absolutely disagree with you on the toe in up front recco. There is NO SITUATION you want toe in up front and these cars already push like a dump truck.

Unless you are a hard core track junky and spend most of your time on track you need to have a street alignment and by all means have nothing other than ZERO (neutral) toe.

My guess is that there are 2 things playing into his problems right now (and I doubt it is the springs or shocks)........ (1)Improper ARB's and drop links....(2) crappy alignment settings that keep getting "guessed". As far as ride height, he might have dropped the car TOO low and does NOT have adjustable toe arms in the rear to bump steer the car properly so his rear toe change is exponential under load. FISSION......can you take a picture of your car from the rear under the car so on a level surface we can see the orientation of the toe arms?

These cars do NOT like half *** pieced together setups. You need to do it properly or leave it at is in STOCK form.

Further, he could have a bad tire issue which is causing his woes. There are just TOO MANY variables that got thrown at it and now it's a fishing expedition.

My recco is to get the alignment situated pronto! Very basic stuff but you need to make sure that is in fact what it is.

Up front? ZERO toe and negative 1-1.5 camber
Rear? 1-2mm toe IN to help with straight line stability. Camber (same as front but you can go up to 2.0).

Check ARB's to make sure they are not loaded in a resting state.

And if all else fails, swing on over to my place and let's go for a drive.

Paul 996

+1 totally agree
This is my guess as well. He has stock C2 ARBs with GT3 Shocks/springs. The closest parallel would be me running my gt3 front bar on soft and disconnecting the rear bar. And yes it would push like crazy!


I really hope that it is not too low since I emailed Dan screen grabs of critical assembly and height measurement pages from my service manual.

LVDell

The frustrating part of this is that his car is setup in such a way that makes it "un-fun" to drive. And nobody wants to see another Porsche brother not have anything other than "fun" when they drive.

We will get this sorted out soon enough but the OP doesn't seem to be approaching this pragmatically. Rather his setup seems to be driven by anecdotal suggestion and personal desire for an outcome not supported by the current potpourri of parts and settings. Maybe the initial desire was based on published settings but that is obviously not where we are.

trackjunky

Dell, somewhat agreed. The difference between zero toe and .03 toe in is miniscule. For example, if a fan is blowing on the side of the car, you could see a .03 change. .03 is almost neutral, but compensates for when the car is depressed and will toe out. Next time your car is aligned, put tension on the wrench and see how easy it is to simply "lean" your way to a .03 change in toe or camber.

Trying to diagnose things over the internet is a challenge, since there are just too many unknowns, but I think we all agree that you must first rule out a simple alignment issue or an improperly installed part, then go look at a part failure.

If, at street speeds, 35-70mph his car is pushing this poorly, then something is very off. Usually these cars will "push like a dump truck" more towards the limit and at track speeds. I've never had my car push on the street. Anywhere. Now at the track, some push.

LVDell

True but he is nowhere near the high lateral G loads to induce a toe out condition up front. That is VERY rare and one I have NEVER experienced on track and that is with lateral G's approaching negative 2! There is absolutely NO REASON to create a toe in situation up front no matter how small. The fact is you still have INCREASED your propensity to understeer with each and every mm past neutral. The ONLY toe settings your car should have up front on a street car are neutral and neutral to slight toe out for the track. I have run both neutral and toe out on track and I much prefer neutral as the benefit of initial turn in is NOT worth instability on high speed straights.

trackjunky

[QUOTE=LVDell;5899011]
As far as ride height, he might have dropped the car TOO low and does NOT have adjustable toe arms in the rear to bump steer the car properly so his rear toe change is exponential under load. FISSION......can you take a picture of your car from the rear under the car so on a level surface we can see the orientation of the toe arms?

Check ARB's to make sure they are not loaded in a resting state.
QUOTE]

Excellent first step.

It's doubtful that he's gone too low, but it's possible. For example, we've gone to almost cup car height and the car still drives fairly well. But, that is with very stiff springs (much stiffer than GT3 stock), so the car may not be bottoming out.

If he went lower than GT3 stock, with anything softer than GT3 stock springs, the car will bottom out the rear suspension under power and the car will push.

LVDell

Cup car height? I assume you have bump steer adjustable toe arms?