According to TireRack.com, it looks like anything wider (and therefore lower-profile) than 255/35 would require at least a 9" rim:
http://www.tirerack.com/tires/Spec....&vehicleSearch=false&fromCompare1=yes&place=0
http://www.tirerack.com/tires/Spec....&vehicleSearch=false&fromCompare1=yes&place=3
http://www.tirerack.com/tires/Spec....&vehicleSearch=false&fromCompare1=yes&place=7