I personally use 275-55VR-15 Pirellis on 8" rear rims. They aren't too big for the rim which supports the casing properly, plus this size is 26-1/2" in dia, which lets the speedometer work perfectly with those highway mile-markers. Sadly, they are no longer available anywhere in the world (in V-speed-rated compounds). Hoosier makes a DOT tire for cometition, but the wear rating is likely to be a matter of days rather than thousands of miles...