How well it works depends on sidewall height. Larger profile sidewalls will accept a narrower wheel easier. It's best to see what the tire manufacturer recommends for your size and make/model if you want to get it right, but 8" should be safe enough to do. You'll probably just notice early tire wear in the center of the tread from the tire bowing out slightly (not dramatically or visibly bowing out in the tread, but the weight would be focused in the center of the tread).
I just looked some tires up, and the manufacturers all recommend 9 to 11 inch wheel widths for 275 width tires, so take from that info what you like.