I am getting ready here in WI to get the snows out for the winter. My snows are 18"s BMW wheels, but, my standard tire is a 20, any concerns or things I am forgetting?

THX in advance for your replies!

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2009 E70 White w/black int
2006 E53 X5 4.8is Sold
2000 SVT Cobra R #193
2003 SVT Mustang convertible