19's don't HAVE to be heavier than 18's. On my 535 I went from the stock 18" wheels with runflats to aftermarket 19's and non runflats...my 19" wheel/tire combo was more that 10 LBS lighter per corner than the stock 18" combo AND with the profiles of tires I selected I matched the overall diameter to stock. The difference in IMPROVED performance over stock could be felt as a reduction of +40 lbs in unsprung weight is a lot
