Allgemeines Diskussions-Forum » Backspacing questions for wheel upgrade

On the rear, I currently have 17x8 with 4.81" backspacing and a 8mm offset. Fits well in the wheel well. I want to go to 17x9.5. Is my math correct in assuming all I really need to do is add 1.5" to the backspacing?

There is a size that has 6.35" backspacing and a 28mm offset. This should fit pretty close to the same, correct? The offset is confusing me.
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