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      11-23-2012, 09:14 AM   #4
mikew2069
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Drives: F30 335i MSport
Join Date: Oct 2012
Location: Houston

iTrader: (1)

245 is the width in MM.... 45 is the ratio to the width that gives the tire wall height. 18 is size of wheel.

245mm X 0.45 = your sidewall height. Take this side wall height, multiply by 2 and add to your wheel size to give you the total diameter of your tire. don't forget to convert mm to inches or visa versa.