Not sure if you know, the offset is the difference between the center of the wheel and the mounting surface of the wheel. A higher number pushes the wheel inward, a lower number pushes the wheel outward.
A 305/35/20 is a big tire, it "fits" on a 10"-wide wheel, but the sidewall bulges, you end up with a much narrower footprint, something around 275mm or so.
A 305/35/20 is a big tire, it "fits" on a 10"-wide wheel, but the sidewall bulges, you end up with a much narrower footprint, something around 275mm or so.
48-50mm is a very safe range for the rear when running a 10"-wide wheel back there.
You start running into issues when you run a 10"-wide (or wider) wheel with an offset of about 40-42mm or less. But only when running a wide tire on that wheel. If I was to have run a 285 tire (285/35/20), even a 40mm offset would've been fine.