Smallest wheels & largest tires for an 09' X6 50i
 

I recently sold my 01 X5 for an 09 X6. I was impressed with the off road capabilities of the X5 and since I do a lot of camping, dirt bike riding, etc., I am interested in picking up a spare set of wheels & tires for my off road trips. Specifically, I was curious to know what would be the smallest wheels that would clear the calipers and with the largest off road tires that would fit. I have the 50i with the sport package and 20" factory wheels currently. Any help would be appreciated. I would also be interested to know if anyone else has attempted a similar setup for off road driving. I have attached an example of an X6 with a similar setup, however, I could not find any particular information on this tire/wheel combo.