Can we just clarify what the normal offset is Would it be 40 by any chance
Anyway the standard offset is of no relevance when you are putting wider wheels than the original 7j ones on! The et40 was obviously chosen to give the correct clearance on both sides of the wheel for the 7j rim and 205 tyre. Try using a 40 with 8j 18's and 215's or wider and i promise you they won't fit without fouling the front suspension and looking stupid