I'm getting 18's
 

what offset should i get?

I am assuming you have a 4th generation maxima. I have 18 X 8.5 and my offset is 35 mm in back & 38 mm in the front. You could even go with a 30 mm offset in the back. My wheels & tires a tucked under the fender no rubbing inside or outside. You can go with a 235/45 or 245/40.

yeah it's for a fourth gen max. Does 18*7.5 with a +45 offset sound like it'll fit.

im running 17x7.5 with 45 offset and im having no problems so far