I did a quick internet search and came up with the below specifications for the stock ISF wheels (I hope they are correct). I imagine that each wheel style is different whether it will clear the breaks or not. I know that others have successfully used 18s before though.
* Size: 19 x 8 Front, 19 x 9 Rear inches
* Bolt Pattern: 5-114.3
* Offset: 45mm Fronts / 55mm Rears
* Accepts TPMS Sensors