I wouldn't do 285 on a 10.5 but that's just me. In fact a member of our car club just posted this pic and asked "this doesn't look right does it?" We all agreed no, it doesn't. To much stretch and I'd be scared of blowing the tire off the bead. I say if you're going to do wheels and tires do it right. In my eyes that's at least 10% over the wheel, yet not above 20%. That puts you at a 295 at least, I like 305 however.
