Hello! im buying these (rota Grids) http://www.my350z.com/forum/wheels-a...0-concave.html

in 18" by 18.5 wide.. .. what offset do I need for infiniti g35x sedan from 2007, also, does any one know what the tire dimensions would be if I wanted to keep the stock rolling diameter of the 17s? so i just need to know the height and width of the tire I would need. Thank you very very much!

 

You would want an offset around 30-35 but i dont think wheeldude has them in that offset for an 18x8.5" but i could be mistaken. For tire size, you would go 245/45/18.

 

can you please explain those numbers? Im a tire newb.. and would those dimensions keep the tire at the same rolling diameter at the stock wheels

 

Read this to understand more about tires.
http://www.discounttire.com/dtcs/infoTireTerm.dos

The rolling diameter of a 245/45/18 is 0.06" smaller than the stock 225/55/17's. It is the closest you'll get to stock diameter.

 

245 is the width of the tire, 45 is the length of the sidewall, and 18 is the diameter of the inner circle (or rim size)