I recently replaced the original tires at 45K miles, and went with a 255-60-18. It fits perfectly - maybe .5" shorter, which is fine. Made a noticeable difference in handling - the car is much more stable now.
That is the OEM size for a BMW X5, which is a similar sized vehicle - slightly smaller even. And I think maybe also the Porsche Cayenne. I went with a passenger car tire from Yokohama - YK580 at Americas Tire (Discount Tire).
Happy so far with them. I would not run them in snow, but I have dedicated snow tires for that when needed. If it ever snows again here in the CA sierra's....