Basically, (in regards to tires rubbing the UCAs) the offset doesn't matter as long as the backspacing is correct. For 285s, 4.25" BS is the sweet spot.
good to know, thanks! I need to measure the backspacing on my current Eagle Alloys with 285s...
Another note.. Offset can get really confusing because it's measured by overall rim width. The reason it's confusing is a 17x8 wheel is actually 9" wide (outside edge to outside edge). A 16x7 is actually 8" wide. In your case, a 17x9 is actually 10" wide.
thanks for the clarification!
My recommendation is.. don't worry about the offset unless you are trying to figure out if the wheels will clear the brake calipers.
I plan to do the 231mm TBU one day, so this is important to me with my current 285s...