Im trying not to sound dumb but if you increase your rim size from 16 to 18 inch that should get you a 2 inch increase of clearance from the bottom of your car and the ground right?
just wondering because of have no idea...im assuming that alot of other things would effect it so im not sure how much of an increase i would see

 

Even though the rim diameter increases, there should not be a significant change in overall wheel diameter. This is possible because the aspect ration of the tire gets smaller (i.e. there is less sidewall to the tire). In the Maxima's case the stock wheels and tires is about 25.3" inches in diameter. The tire size is 215/55/16. So to calculate total wheel/tire diameter do the following:

width*aspect_ratio*2/25.4+wheel_diameter
215*0.55*2/25.4+16=25.3"

Going to an 18" wheel, you would need a wider, lower profile tire. 235/40/18

This way the speedometer and odometer are not significantly affected. By going to the larger wheel and tire package, the car should handle better with more grip. However, there will be a harsher ride and probably a little slower acceleration because the larger wheels and tires are generally heavier that the ones being replaced.

 

Personally, I noticed that my tires were at least an inch larger than my stock 16". I put them next to each other to make sure. My car sat about 1/2 inch to an inch higher before I had my car dropped.

I wouldn't say it was 2 inches though.