Originally Posted by FStop7
Not at all true.
It is not true? Are you saying that a cast wheel is stronger than a forged wheel?
In this case, the question was... will the cast 19" wheel will be lighter than the forged 19" wheel.
All things being equal, the cast wheel will NOT be lighter than a forged wheel of the same size. However, in the event that is it, the cast wheel achieved its low weight because it may have less material, therefore, less material normally mean less rigidity in the wheel which may cause a wheel to bend or be structurally weaker.
If you think that BMW made a cast wheel that is lighter and stronger than the more expensive, super light forged wheel, then I think you are wrong.
Consider other wheel manufacturers like BBS and HRE, who are in the top echelon of wheel making. They too have trouble getting a comparable forged monobloc wheel to be lighter than the stock forged 19"s. The only wheels that I have read about being lighter and stronger are the RAC wheels in the current GB.