Question about tire fitments (rim/tire)

275's on an 8" wheel has been done. Plenty of guys are riding around in them.

However, it's not generally acceptable and handling may suffer because the sidewall bulge may allow the tire to roll over onto itself in a hard corner...which is why many consider it unsafe.

For a 275, a 9" wheel is really required. Max recommended for an 8" wide rim is 255.
 
It can be done, yes, but it won't bennifit you over a smaller size because the footprint will be distorted and you will probally have less traction, the tire will wear unevenly, and it will not handle that well. So the footprint will actually be smaller.

The lower the profile you go, the more picky the wheel size is. 245/45 is perfect for a 8" wide 17" wheel. 275/40 is perfect for a 9" wide wheel, and a 315/35 is perfect for a 11" wide wheel.