Just got back from the alignment shop, got the front end dialed in near perfect! Cost only $38.00!! Rear camber is -1.50 left and right. In order to get it into "acceptable" limits, I need to lose 1 degree or 60 minutes of camber. The stock shim that is in the car is a 2mm. As I understand it, for each 1mm of shim I will get 10" of camber change. If that's correct, I will need to add 6mm of shim to each side! Problem is that I can only find shims as large 4mm. Is it acceptable to stack shims? Say 2 or even 3 shims on each side to total up to the required amount, or do you need to use a single shim?

Absolutely, that is why they sell different sizes, I have like 3 on each side of mine.

mine had three on each side. Now it has 2 1/4 camber on the rear to clear properly.

Yup I have 2 thick and one thin. going to put in 1 thick and 2 thin this weekend.
If you go screw around with replacing shims YOU WILL SCREW UP that perfect alignment. My personal opinion is .... 1.5 is just fine. Go autocross it and then you will want more

What is the spec @ ride height? The trailing arm has 1 1/2 degrees built into it as it is, but that's dependant on the mounting points.

Andy

so what you are saying is that 1.5 is ok for everyday driving, but won't my tires wear badly?

Call Chris at Tangerine Racing.

http://www.tangerineracing.com/

He is a member here too. Just tell him how many shims you need to adjust it to and he then will make you a new solid trailing arm bracket that will be much closer to what you need.

http://www.tangerineracing.com/suspension.htm

Then you may only need a much thinner shim or two. They are $200 a pair and stronger than the stamped stock part.

If you want to do it right you will need to raise the rear suspension points by three inches. Chris sells or will be selling a kit that once welded in will do this too.

It just depends how $$$ you want to go.

so is the car ok to drive around in for a couple weeks until I get around to getting the shims? I wont hurt the car or anything will I?

-1.5 won't hurt anything. I run -2 front and -2.5 back on my Boxster and it runs fine. I am probably wearing down the inside edges of my tires a bit on the street, but I more than make up for it by wearing the outside edges on the track and at autocrosses.

So what is a good measure for neg camber on the rear for mild to aggressive street driving?

Zackly what you got. Just drive it and love it. any good on.off ramp will probably stand the tire straight up anyway. if not DRIVE HARDER.