The problem here is that the offset of a wheel does not guarantee it's ability to clear your brakes, it is merely a measurement of the relationship of the bolt-face of the wheel and the centreline of the wheel,
for frontwheel drive cars offset is positive, therefore the bolt face is nearer the outside of the wheel, how the wheel is constructed has more of an impact on whether your brakes will catch, a lot of modern alloys have very curved blades in order to achieve the deep dish look that is associated with negative offset wheels (usually found on the rear of v powerful rear wheel drive cars) ie F40, these can catch your brakes if the radius is so severe that they need to be made very heavy gauge in order to have structural rigidity.
So as stated above, a spacer will reduce the measurement 'c' below, by moving the left hand red line defining 'c' to the right.....
It's what the metal to the left of this line is doing that I would guess is causing your catchin'
