<ul><li><a href="http://forums.audiworld.com/allroad/msgs/141376.phtml">some explaination.</a></li></ul>

You may want to try this link to see the effect on inner clearance and outer position when changing wheel sizes.<ul><li><a href="http://www.1010tires.com/WheelOffsetCalculator.asp">http://www.1010tires.com/WheelOffsetCalculator.asp</a</li></ul>

spacers and that was the correct fit. I did run 20mm later on and it worked fine too with plenty of clearance all around.