18.5 would be too big even for most widebodies
....j/k I know you mean 8.5". Those offsets seem like conservative good numbers to me on those wheel widths.
As to clearing the calipers, keep in mind that you absolutely cannot tell that from wheel offset or width information. You just have to ask the manufacturer, seller, or find somebody who tried that wheel and knows. Wheels with the same exact offset and width ...one can clear the brakes and one will not, it depends on the design of the wheel and how the "spokes" transition from the hub to the rim.