FR611 north of Demott CG. Do not try FR610 unless you have a crazy Bronco or Range Rover or Hummer! I damn near got stuck all night there and just made it back because there are no turnaround points, especially for anything over 22 ft. Not for the faint of heart or low riding rigs. I have a 25 ft total car and Teardrop trailer length and it was challenging but I found one spot. The views are literally indescribable. I sat there and stood there for 12 hours watching the Grand Canyon change every 30 seconds due to clouds and sun. I highly recommend this if you can get there because it was an incredibly memorable experience. The people at the Grand Canyon Lodge on the north rim were very helpful in helping me find the route and it's only about 7 miles from the Grand Canyon Lodge to the entrance to the really rough road. And then, it's about 12 miles in!