The first 1/3 and last 1/3 of this route is a manageable gravel bike route (graded gravel road, dirt 4WD double track, and a welcome couple miles of paved road), but the middle 1/3 cannot by any stretch of the imagination be considered a gravel bike trail. I wouldn't even dream of doing some parts of it with a downhill mountain bike. It is down a steep, narrow canyon hiking trail. Toward the bottom, it is more manageable. So, plan on walking your bike down a couple miles of this single track. That would be in the counterclockwise direction. Don't even think of doing it in the clockwise direction unless carrying your bike up a thousand vertical feet sounds fun to you. Fortunately, the rest of the ride is true gravel bike bliss if you are fairly well conditioned and have low gears on your bike. The whole route would probably be a bit more fun on an XC mountain bike, but it's doable on a gravel bike (other than the steep canyon single track descent). Again, take this ride in the COUNTERCLOCKWISE direction. If you don't, you'll be very unhappy... and tired. Oh, and if you get to the single track portion, look down the trail, and think it looks scary... just turn back and take it as an out and back route. That single track only gets worse.