Here is the suspenion setup I have on my car:
H&R sport springs, KYB GR-2 shocks, ingals front camber kit, rear ($15) camber kit. I currenty have some 03 Eclipse GT 17" wheels on the car. They are 17x6, nice rims but the tires suck.

I just got some RX7 wheels 16x8 with Dunlop SP5000 225/50/16. These are the stock size tires from the RX7. The tires on the front rub a little when the wheels is turned all the way left or right. So i put them on and did a few launches they grip great.

But when I put the RX7 wheels on the rear they rub like Anna Nicole thighs. The tires are rubbing against the suspension arm that goes up and down. What size spacers do I need for the rear???

1/8th inch spacers did the job just fine for me, but if those tires are a bit wider you might need 1/4 inch spacers, which should still be fine if you use an aftermarket cone shaped lug nut which gives you enough turns on the wheel stud.

"Tutto fa brodo."

Todd Scungio
98 RS
15.173 @ 90.70 MPH

And also a 2011 Ralliart