I had the same issue that drove me crazy until I finally figured it out.
1. Measure hub opening on wheel
2. Is there a difference between this and your your hub size?
3. If so go to this website
http://www.justforwheels.com/hub-centric-rings.jsp and buy hub centric rings that make up the difference and problem solved.
I had a set of custom rims that were supposed to be hub centric but weren't and caused me to balance my front wheels over and over.