The standard winter wheel/tire package provided by BMW Canada for the E53 4.4 is 18". In my case, it is 18" BMW Style 74 wheels with 255-55-18 Pirelli Scorpion Ice and Snow. Great package for the snow and looks good too.

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2005 X5 4.4 (Sterling on Truffle) w/sport everything
2011 Audi S4 (Prestige, DSG)
2012 Audi Q7 (Sport, S-Line)