i purchased rx-8 rims with tires, but I ended with Motegi DP12 hyperblack rims instead, but kept the same tires.
I had to roll the rear fenders , the ride quality is nothing like 17s. Often my CD player would skip on bumpy roads. Something that wouldnt happen often on the 17s. (I live in Montreal Canada, roads are like war zones) My car rattles much more now, especially the dash.
I attribute the effects to the 18s rims. I have not lowered my car, I cant imagine how it would feel like with my mazdaspeed springs.
I also noticed that after I put the 18s, it is harder to turn the wheel.
A) my rear fenders are rolled
B) ride quality is comprised
C) Much more road noise.
That may be only me....
Am I satisfied? For look yes, for comfort no. Overall, OKAY