Wheel spacers

Ok guys need some help here. Just got my wheels they are Speedline corse 2118's 15x7+53 so I know i am going to need spacers. Where have you guys gotten spacers from and how big of a spacer will I need?

Here is what they look like
https://scontent-a-sjc.xx.fbcdn.net/hph ... 6130_n.jpg

Measure the mounting surface of the wheel, out to the inner edge. Then measure the mounting surface of the brake rotor (use a straight edge), out to your shock/spring/suspension where it would touch the wheel edge. Use those two measurements to decide the spacer needed to keep the wheel from touching anything. HTH