This weekend I tested my new rim/tire rear clearance with the combo that will go on the vehicle. The pictures below show that there is some serious meat on the rears. That it stands taller then stock is no surprise. The online size calculators that I used confirmed that.
Volk Racing GT-C 18x10 +44
BFGoodridge g-force KDW 275/35/18
Eibach Springs
Tokico Illumina II
I was a little worried about clearance from the inner side of the rim/tire to the shock housing. My mistake was taking the measurement when the car was on a jack and the rear suspension was fully extended. When the suspension has the full load of the car, I have about 1 inch of clearance.
The clearance from the top of the tire to the bottom of the fender is 1.5 inch.
If you look at the installed wheel from the rear, the rubber sticks out beyond the stock mud flap (for lack of a better term). Since I will be using the Bomex Rear Under Covers, I do not forsee this to be much of an irregularity. We'll see.