For everyone asking how big of a spacer to get... measure it first. This will get you in the ball park of what you need.
Grab a long straight edge (piece of wood, even a cardboard box) and a tape measure/ruler. Hold the straight edge against the fender and straight down. Then measure the distance between the wheel/tire and the straight edge. I always measure from whatever point sticks out furthest. In this case, the rim since the tires are stretched.
So as you can see, if I want this rim to be in line with the fender, I need a 10mm spacer.