i just bought rims for my 1987 mazda rx7. the rims are 18x7.5, i wanted to know if i should go with 225/40/18 tires or 235/40/18.

my second question is about lowering springs. im ready to buy a set of arospeed lowering springs, but they drop 2.0 inches. with me using an 18" tire. i want to make sure that dropping the car 2.0 inches is not too much. i dont want the tires to rub the body from the 2.0 inch drop.
can anybody give me any ideas. i have the rims already. im ready to buy the springs and tires now, but i want some input from you guys before i buy. i dont want to mess anything up.
if anybody has any pics of different set-up, please post. thank you in advance for the help.