S14specR

i recently purchased some 18's but they are 18x7.5 are they gonna be any good on the 240 and what tire size should i get??

Silviaspeed

They will fit fine on your car. The 240 can handle up to 285(i've heard to 295 also) in the rear and like 255 up front. All you need is some nice rims now to go with your tires. Just find some rims to match the 7.5" width and you'll be all set.

S14specR

sorry i meant the wheels is what i have not tires. 18x7.5 konig tantrums.

Import Fanatix

7.5" rims I would go past 245/35 in the rear and 225/35 in the front. This will give you some rubber for the street so you wouldn't bend those rims.

thoraxe

do a google search for tiresize calc

and remember that you are driving a 240SX not a corvette, and that you aren't gonna use (power wise) much more than a 225 or 235.