Kind of a bummer, it doesn't go down to 125 section width. One common Mercedes spare size is 125/90-16 but a 225/50-16 is basically the same diameter and is very common. (125*.9 = 112.5 same as 225*.5)
That site has the simplest way to quickly show rim clearance and backspacing issues. I need to plug in actual crossfire stock rim sizes now.