Blacksport350

Okay, in an effort to dial out my handling gripes, we have managed to make it worse. I went to a local GT3 experienced set up shop for a corner weight and alignment. My orginal intentions were to use the Roland Kussumaul specs but as this is an 80% street driven car, they talked me out of it and into the following:

Camber front: -1.6 -1.6
Caster: 8.4 8.1
Toe Front: .05 .05
Total Toe: .10

Rear Camber: -2.0 -2.0
Rear Toe: .11 .10
Total Toe: .21

Coner weights(1/2 tank+driver):

640LF 580RF
1045LR 1023RR

The car appears stable at high speed in s straight line but is still whacked in the twisties. If you lift at all in a lower speed tighter corner, it is as if someone gave the steering wheel a quick tug(big surprise the first time after it was set up). This is a new issue.

The orginal gripe of pulling the front end light under throttle application in lower speed corners coming accross the apex got worse. With a 1/2 tank of fuel, it now feels like it did before with under 1/4 tank.

The diagonal corner weights and left side weight could hardly be better. My actual weights are a little different from the above(going of memory) but it was 49.8% and 49.9% for the corner cross weights. Left side weight is 51% which could hardly be better on a street car!

Okay, I am open to any suggestions here as I am getting frustrated chasing around gremlins on an otherwise great car.

Tires are MPSs running stock pressure.

The shop suggested taking some camber out of the front or changing the toe. It is almost feels like there is an issue with the thrust angle but I asume that was checked and is fine. There are no suspension or bushing issues that I am aware of that could explain what I am feeling.

Thanks in advance if anyone has input or setups that work!

MetalSolid

Numbers look ok... Tire pressures?

Try reducing front toe by 0.02 L/R, setting rear toe to 0.16 L/R and lowering front to Roland Kussumaul specs.

Larry Herman

I ran my GT3 with 0 front toe, as it really helped the turn-in, and it didn't wander at high speeds. I am curious about the "someone gave the steering wheel a quick tug" comment. Can you elaborate, as it is unclear what exactly is happening. BTW less front camber will make your problems worse; why would they suggest that?

Blacksport350

The best way trhat I can explain it is an exagerated throttle steer condition. In other words, take your foot out of it and the car just turns in harder and abruptly. I have not run into a condition like this before. If I didn't know better, I would say there is a bad bushing in the rear suspenion that is moving based on load. But as the problem wasn't their pre setup, I am pretty sure that isn't it.

Not sure why they would suggest less negative. I would guess less toe would help.

THe back actually wasn't touched as they were happy with it.

Blacksport350

Tire pressures are being run to stock specs and are not off.

Where does Porsche measure ride height from?

It was close to Kussumaul specs before but with the corner balancing, that has changed the respective heights by 1/4-3/8" from spec to get the 50%-50% digonal weighting.

NJ-GT

In my opinion, your numbers are not ok.

Currently, I'm running 0.08 degrees toe-out per side at the front. I made this change recently to improve the turn-in response for Solo events, even though I'm running 10" wheels with 285/30R18 tires, I was having a minor initial understeer issue. The car still drives as a limousine on the road, due to the bump steer reduction on the last setup.

I've not driven at the track with this setup yet, but I expect no surprises, because two GT3 Cups at the Speed WC are running more toe-out at the front than I do.

Your rear numbers are a problem. You need twice as much toe-in. Shoot for 0.25 degrees per side (0.50 degrees total toe-in). Anything from 0.15 degrees or less per side, will result on a twitchy car.

Please, inspect the four eccentic bolts, two for camber and two for toe. When they wear out, regardless of the static alignment settings, the car will be unsafe and undriveable.

Z06

I run my car at Mosport which is a bumpy track with allot of elevation changes the long straight is good for 145+mph..

I have slight toe in on the front with -3.5 and -2.5 camber, rear toe which I thought was low was 9 min.. the rear toe you have should work.
The car is a daily driver, even tire wear.. it could be different if you do allot of hyway driving.

My friend has the same problem...try going to another alignment shop, these cars are very sensitive to alignment ..you may be surprised.

Blacksport350

I am not surprised at all. A GT3 when it is dialed in, is a dream. When they are off, they are a handful and then some!

Blacksport350

What do you look for? On our race car, they are worn out when they will no longer hold an alignment setting or worse, move and cause the alignment to change under varying loads. My rear has never been aligned and appears to have held very well. Is there something else I should look for?

Frankly, the car almost feels as if something is loose but all appears to be spot on. So far, it has 9500 miles of mostly abuse free driving.

db_gt3

A few questions,
Have you tracked the car yet? Where do you plan on tracking it?
Where are you located and who is doing this work for you?
A few basics to keep in mind when talking alignment on a GT3:

Front caster is non-adjustable.
Rear toe is also non-adjustable.
Front toe should be ZERO when under full vehicle weight.
A good camber set up for track work would be: Front -2.6deg./ Rear -2.1deg. You will need shims to acheive this. Lots of them.

Corner weighing is fine but unless you are driving at a very high level, you will not get any benefit. Running more camber in the rear sounds very unusual. The standard for track setup is always .5-1deg. more in front for these cars.

Toe in will be more stable on the straights and under heavy braking, but steering will not be as nuetral.

I would look into who is the most experienced Porsche tech at your dealership(preferably someone with a lot of track and GT3 experience). These guys you are dealing with sound like hacks; just the fact that they would recommend more camber in the rear tells me they are suspect and do not know what a sound GT3 track setup should be.

As far as lifting in a corner, well, this is sort of 911 basics. This will cause the rears to lose traction and thus the heavy back end will begin to go around, feeling like massive oversteer. You should be lifting prior to entering a corner, apexing late while trail braking(if you are smooth enough with your inputs), and applying power increasingly all the way from apex through exit.

Hope this helps. If you are in SoCal I know the best guy to get this sorted for you.

Blacksport350

Thanks for the post!

I have tracked the GT3 and live in Colorado. When pushed up towards its limits, it fell into a nice groove and was a joy. When driven down below its limits or in the bends on the streets, it is simply not there but I know it can be.

I will point out that this is not a driver issue(I do not brake in corners, I trasnition smoothly to the throttle, etc), I have just been using some examples of what is really unsettling the car as I think this can help to better explain an issue.

The GT3 is not my race car, it is my fun street machine so I need a setup that works for the street 90% and track 10%.

As to the corner balancing, I did this out of habbit and am aware that it helps very little unless you are on R compounds puchig the limit but why not do it anyway.

The shop actually was recommending to take some of the camber back out of the front(back towards stock(1*) and also taking out a little toe.

Right now the car exhibits the following issues:

1. Any application of throttle off the apex of a lower speed corner will cause the front to lift bigtime, no issues in higher speed corners. This has always been there.

2. Any lift of throttle even in a gradual sweeper(where you should be able to shift with weight transfer) causes the car to turn in to the corner abruptly. It is NOT an oversteer condition, it is a directional stability issue. This is new.

It does fine under threshold braking on uneven surfaces and straight line at speed.

The guys I am using are GT3 experienced and short of the local Cup car guys, are probably the most experienced around for Porsches and GT3s specifically.

db_gt3

I must admit I am a bit confused. It sounds like you are really more interested in getting the car to be more compliant on the streets at lower speeds, rather than getting a good track setup dialed in? You cant really have it both ways. If this is the case you should still have more camber in front; perhaps -1.5deg front and -1deg rear. This will give you a more balanced car as the fronts are doing the steering and thus require more camber than the rears. Taking more camber out of your already rear biased setup would make for an even more unbalanced car.

This car is a bitch to drive on uneven surfaced roads and will pull from the slightest ripple in the pavement. The more camber you run in front the more pronounced this will become.

If the shop you are going to has experience with GT3 for street/track they would be able to tell you all of this regarding street compliance vs. trackworthiness and the inherent trade-offs you will have to live with for one or the other.

Of course the front is going to lift upon throttle application out of a slow corner; it is a rear engine 400hp car.

If I were you, I would go to the Cup Car guys. I would maintain that the guys who recommended your current setup are hacks; no matter how many GT3s they have "setup" in a similar fashion.

Phokaioglaukos

Not to hijack this thread entirely, but for a car with RA1s on the track and in driving to/from the track, how do these settings look (and what do they really mean?):

LF (RF)
-1.2 (-1.2) degree Camber
8.3 (7.7) degree Caster
0.05 (0.07) degree Toe
18.7 (19.1) degree SAI
17.4 (17.8) degree Incuded Angle

Front
0.0 degree Cross Camber
0.6 degree Cross Caster
0.12 degree Total Toe
0.02 degree Set Back

LR (RR)
-2.0 (-2.1) degree Camber
0.08 (0.13) degree Toe

Rear
0.21 degree Total Toe
-0.02 degree Thrust Angle

Bob Rouleau

Blacksport - Your alignment settings are not bad as a street/track compromise. I prefer more rear toe in myself, the car is more stable when you lift. I run 34 mins total (17 per side). To the gentleman (db-GT3) who says rear toe is NOT adjustable, I say 'huh"?

You say tire pressures are stock. Cup tires should be 32F 34R HOT pressure. If you are higher than that your car will be twitchy. Street tires should never be above 40 hot. My car likes 36F 38R HOT on Michelin PS2.

I also caution against zero front toe if you drive on the street, the car will turn in well but straight line directional control will be compromised. The GT3 turns in fine if you drive it correctly and only the autocross experts NJ for example who deal with slow, tight turrns mostly like any toe out.

What are your sway bar settings? I like one from full stiff in front and two holes from stiff in back.

One last thing, the GT3 has a lot of compression, if you lift even a little abruptly while the car is still pulling some lateral G's it will twitch due to the abrupt weight transfer caused by the high compression drag on the rear wheels.

regards,

db_gt3

My most trusted and well respected mechanic explained that my rear toe should be left alone as it is a result of how the kinematic toe link adjusts to ride height and camber. He was happy with the overall setup as it was supplied from the factory in combination with his adjustments to camber and ride height. Unless I am forgetting something, this is how toe is "adjusted" in the rear. That being said, there is no "toe adjustment" for the rear suspension. It is a constantly variable value based on the aforementioned settings as it changes through the travel of the rear suspension. You can measure it from a standstill, but you are only getting a static impression of what the kinematic toe link is doing while driving.

Does that make sense?