I Drive a 4wd toyota pickup and the manufacturer tire size is 215/65/15 but I have run the General Grabber AT2 size 325/80/16 load range D, for the past year and absolutley love them. There was not a selection for extreme offroad. About everyweekend these things drive me about 200 miles on road and about 20 miles on rugged offroad coarses. I have run over jagged tree stumps and been through mud 2 feet deep. These are the best all around tire. I tried the Mickey Thompson MTZ which acted the same on snow and on off road as the AT2 but, the AT2 is much quiter on road and promotes better fuel economy by about 1 mpg. I love these tires and have had them for about 45,000 miles and I am about ready for a new pair.