Problem with 18" PS2's (not N-Spec)

[TriGem2k]

Originally Posted by TriGem2k

2001 Boxster, 43,430miles, Car has never been tracked. The roads in California aren’t bad at all. I’ve actually noticed that the shimmy occurs more severe on different types of road surfaces, the car only shimmies around the 3,000-3,400RPM range. I’ve had 3 types of different wheels on the car. The first being 18" turbo Twist that came from the factory. Sold them only because I had an incredible offer on them. I was given a set of 2001 17" Boxster wheels as part of the deal. Now just recently (2-3months ago) bought a set of 18" O.Z. Racing wheels. I’ve gone through over 10sets of different tires/brands/models. I’ve used standard sizes for the most part. The only time that a non standard size was used was on the 17" Boxster wheels. I ran a 225/45/17 in the front rather than a 205/50/17. Right now I am thinking about pushing a 285/30/18 in the rears on my 18X10s for my net set coming up soon. The car was bought new with an extended warranty that just ended 9/10/05 .

Oh almost forgot the car has had 3 different suspension set ups as well.... 1st being the stock. 2nd was H&R Springs with Bilstein Shocks. Now running Bilstein PSS9... Next comes the H&R Coilovers....

Jim, any thoughts?