When using the 15mm and 20mm spacers the wheel studs from the factory hub protrude beyond the spacer.

This can prevent the wheel from sitting flush to the spacer. Your wheel will need a recession in the back like below to fit correctly or you will need to buy a thicker spacer size.

If you do find your self in this situation measure the total wheel stud length from the face of the rotor to the end of the stud. This measurement will help us get you a spacer that will fit correctly.