Jean

Anir,
You can use these settings with 245 or 265 irrespectively. I have also a set of 235s and 295s Corsas on my Mag GT2 wheels and the balance is just as good.
I don't know if this is the best setting at all, I know that one of the best Porsche race shops in Germany set it up for me specifically to cure such problems, as well as having a great track setup (not pure race). I did change a LOT of other suspension parts as well, but unrelated to this specific problem.

I have a conservative (-2) camber front and rear and 8 min Fr. toe, Caster is per RS specs. Height is about RS height, and I don't need EVO uprights. I even asked them since I wanted to buy a set but they said there is no need. The car handles very well on both soft and hard settings and with both sets of wheels and tires.

As Bob said, I would try a good suspension setup and if it does not work, go for the uprights, bump steer can be dangerous.
Jean

pstoppani

My first question would be, when did this start?

Did it start after you accident? Maybe the chassis is damanged and needs to be straightened? Take it to a chassis alignment machine at a good body shop.

You alighnment seems reasonable. But, after checking the chassis, I'd go for stock ROW or US alignment. If the problem goes a way you can incrementally go more aggressive. Not cheap though...

Finally, sorry you're have these problems... Always a pain and takes away the joy of driving the car. Best wishes on finding a solution.

Anir

Jean,

Thank you for alignment settings and feedback.

Pete,

I was also worried about possible accident effects, but I've been assured independently by 3 shops that the frame is straight and the alignment is within specs. Hopefully, they are right. I'll raise the ride height, realign, and recorner and let ya'll know how it turns out. Thank you again for the support and all the help. I love this car and want it to be right. After all, it's got to serve the family for at least another 40 years.

pstoppani

The other thing to check is all bushings and the wheel bearings; you might start there since everyone is telling you that the alignment and frame are ok.

BTW - A final note on bump steer. Unlike kickback and skitishness, bumpsteer does not have steering wheel movement as a symptom. That is why it is dangerous; your car turns but the steering wheel does not. As far as I can tell from your symptoms, you have too much kickback and skitish (wandering) car and the steering wheel does move in these... right?

Anir

Will do. Thanks!

Good point. Most of my problem is indeed associated with steering wheel movement.

Anir

I wanted to provide an update, and thank everyone for their helpful input.

Basically, after a ride height adjustment, and a methodical alignment and corner balancing by an awesome gentleman named Chris at Porsche of Lexington, the car drives like new again. All bushings and bearings were fine (the right side bearings were replaced after the Road America shunt).

The previous Cincinnati race shop had apparently set up the car at even lower than RS spec. Even after a 20-25 mm ride height adjustment, my car now sits slightly lower than ROW sport, at 142 mm front and 125 rear. It still looks great, and the suspension doesn't bottom out anymore and the tie rods sit much closer to horizontal than before.

The previous alignment was totally cocked, possibly as a result of the extreme lowering. It's no wonder if drove so weird.

Before:

Front camber L -0.7, R -0.6 // Caster L 5.2, R 5.4 // Toe L +0.12, R -0.05
Rear camber R -1.4, R -2.0 // Toe L 0.19, R 0.34 // Total toe 0.53 // Thrust Angle -0.07

And after the alignment:

Front camber L -0.4, R -0.4 // Caster L 5.5, R 5.4 // Toe L +0.03, R +0.02
Rear camber R -1.3, R -1.4 // Toe L 0.19, R 0.17 // Total toe 0.36 // Thrust Angle -0.01

The corner balancing is now (Porsche recommends side-to-side weight within 44 lbs):

LF 709 RF 676
LR 1067 RR 1040

Man, I haven't been this happy in 2 years. It's so nice to get my girl back into proper shape again!

As an aside, one of the principals of our dealership is Brian Cunningham - the grandson of Briggs. I've always wanted an early 1950's Cunningham C3. It was cool to talk with Brian, who is an all-around nice guy and fellow race nut. More info

Thanks again to all the cool Rennlisters who pitched in.

chris walrod

Anir, this is great news! Glad to hear of a good result!
Thanks for the conclusion!

viperbob

That is great Anir. Glad it is bringing a smile back to you...

Just a small clarification. The 44 lbs is the cross diagonal weight difference that you want to achieve. So LF+RR vs. RF+LR. Yours is in good shape...

Anir

Cool...I didn't know that. That's even better (only a 6 lb difference).

sonny1

Hey Jean amigo,
Do you have spherical bearings on your suspension arms?? if so I will say kinematic adjustment is not an issue,'cause you no longer have the compliance off the rubber bushes in the rear, 'cause that may be the reason for those align. specs., funny it is 'cause I have very,almost identical align specs on mine, the only diff is that I have evo uprights,spherical bearings all around and the smart racing tie rods up front, probably you too exept the uprights.,kind regards, Sonny.