Here's my story.

I purchased my Cayman S used over the summer. Since I've never had one, I never knew what one should drive like.

The main problem I have had with the car is when I accellerate through an apex, the rear end washes out. Or, to put another way, I have a severe oversteer.

My first though was that this must be the open ended differential issue. So, I ordered and had the Quaife installed. It helped quite a bit, but didn't solve the problem.

So, my next thought was suspension. Had my intensions on the PSS9's, but came across a set of used JIC Cross coilovers for the same price and jumped on the deal.

My mechanic is a serious Porsche tuner. He has set up a winning Le Mans GT3, and has several race prepped 911's in various stages of preparation. The guy knows how to set up a car.

I left him my Cayman a week ago for mounting and corner balancing. At first he said he couldn't get the car set up right. The toe wasn't right. He installed an adjustable rear toe link and now said the car is set up perfectly.

However, he can't get the rear end from oversteering, or sliding out. He has used all 15 suspension adjustments to screw with it, and it doens't help the rear end to hook up. He said he doesn't want to give me the car back because he thinks it's unsafe. So he keeps working on it, on his own dime, and can't get it to stop over steering.

We had a conversation about a rear adjustable sway bar, but he doesn't want me to spend anymore of my money because he's not sure it will help. So, on his own valition and to satisfy his curiosity, he disconnects the rear sway bar altogether, and it still oversteers in corners under accelaration.

He said he's running out of ideas. He thinks it could be a bad set of tires, but doesn't want me to spend the money on a new set as my rear tires have a good amount of tread on them.

The rear tires are Pilot PS-1's. He said he's seen a problem with that tire where the steel belts separate inside the tire and cause this very symptom.

Before we go to the next step, or I buy tires, I wanted to find out if someone in Las Vegas can help me out and meet me at the shop to swap tires/rims for a test run to ferret this problem out. It would be a huge help. Anyone?

Also, if anyone else has experienced anything like this, please let me know.

I really appreciate your help in advance.

Brian

We have seen very few complaints of over-steering in this forum - more folks have had to work a bit at reducing under-steer. Also most here seem to have PS-2s on their cars, with few complaints. Are your PS-1s a Porsche-approved tire for the Cayman? I don't believe so. Perhaps the tires are your problem. You might PM beez - he is very experienced and lives in Las Vegas.
Marty

Before I even finished reading your post I was going to say that it sounds like a tire problem to me, one where the backend is losing grip as compared to the front end, are the front tires also PS-1's? or are they PS-2's? I would try a tire/wheel swap with a local member and compare cars and see what happens. It is either that or someone gave you a bunch of HP that is causing the rear to brake loose all the time.

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K-Man S

Brians - give me a call at (702) 496-5269. I have a 08 CS in Las Vegas w/KW Var3 and other mods.Willing to let you try my setup 19x8.5 & 19x10.5 w/ 245 & 285 KDW2's. I'm interested in driving your lmtd slip setup since I plan to do this mod next.

Just gave you a call. Anytime today or tomorrow would be great. Premier Sports Car Service is off of I-15 & Russell. Happy to meet you down there for the wheel swap/test drive. You are more than welcome to try the Quaife setup in my car. My number is (702) 400-2818. Thanks, Brian

That "issue" sounds familar to me. I think you cant overcome the laws of physics. But I am talking at very tight turn, and wash down pavement surfaces. I have sway bars front and back, and still have some oversteering, but only in very few tight corners. But I can also see a GT3 or even the turbo doing the same thing.

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QFT

Well, good and bad news. DesertCaymanS graciously met me down at the shop. My mechanic went to swap the wheels, and his don't fit because he some really sweet after market wheels (Valero?) and the rears were rubbing my fatter JIC Cross' (he has KW Varient 3's). The good news is his car doesn't oversteer unless really provoked. The bad news is mine does with hardly any throttle imput.

I emaild Beez. Maybe he can meet me at the shop to lend a hand. My mechanic is going kind of nuts.

Brian

Makes no sense at all-

I've got -2.6 camber in front, -1.5 in back, significantly increased rear sway bar relative to front and still have understeer in a skidpad test.

And I know of no need for special parts to adjust toe- mine adjusts just fine and more than anyone would want.

I don't trust your mechanic. I think he has stolen your car and is enjoying it without you.

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996 GT3 lower control arms at all corners
997 GT3 front sway bar
Tarett rear toe links
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DMC harness bar/G-force harness

New update on the tire issue. It isn't the tires. First of all, they are PS2's, not PS1's. Secondly, my mechanic sourced a 9/10's new used set of PS2's for the rear for $80. Swapped out the tires and went for a ride.

NO CHANGE!!!!

My mechanic has charged me for the alignment and the toe parts, plus the labor to install, and that is it.

I went through the undercarige with one of his employees and he tightened and checked every bolt. Nothing looks out of place.

He said he is determined to solve the problem on his own dime. I drove the car home and the set up is beautiful. I just can't give it any kind of power coming out of a corner until the wheels are almost pointed straight, or else the rear end breaks loose.

Ideas anyone?

Sounds like you need to take off all the aftermarket stuff. Get a dealer to reset your specs and go from there. I don't think your "mechanic" is doing you any favors.

Santa Fe may be right. My first thought was that the "PS1" tires (which I'd never heard of) were the problem. But then we learned that they were PS2s, and we already knew that the car had extreme oversteer after you bought it used. Even if you were using too much throttle in turns, the PSM should be operating to keep the rear from coming around, but that's apparently not the case. My thought now is that something on the car is very wrong, starting with PSM. If that's the case, the dealer that you bought the car from should fix it.