Eh? Staggered wheels do not use the same tire size all the way around. A wider wheel must use a tire with a larger section width in order to match the bead and hold air in the tire.

The 335 9" uses 255/50-19, 10" uses 285/45-19.

Just like for 214 20" staggered: 9": 275/40-20 10": 315/35-20

If you have 255 all around (written on the tire), that is 255mm, or ~10". Now, that's the section width of the TIRE, not the width of the rim. X5 10" rims take 315s=315mm=12.4". (Little wider rim, little fatter tire...)

If you put a 255 (10") tire on a 10" rim, it wouldn't hold air.

Perhaps I may not know exactly the width of the rim from the section width of the tire, but I DO know that if I have the same section width on all the tires on my car, all the rims on the car are the same width.

And, given those previous two statements, given that we know that a 255 tire can't run on a 10" wide rim, and all I have left is to be running 9" all around (because the only choice I have for 335 is 9" or 10").

Is there a flaw in that logic?

However, I did as you suggested and went out and did my best to measure the width of the rims mounted on my car. Both front and rear appeared to be 10". HOWEVER, that is the "overall rim width". The number that we are concerned with here is the "rim width", which is measured from the inside shoulder to the inside shoulder of the rim lip, which can only be done if you remove the tire. If the overall rim width is 10", then there is no way that the rim width can be 10". Which again, doesn't guarantee that my rims are 9", but by process of elimination with these specific wheels, leaves us with 9".

So -- 9" all around for the 35i Sport Activity also? (since there's 255/50-19s all around)