Gray Butte Loop Professional Review and Guide
"The outing involves a loop of 7.1 miles, and a 2 mile out-and-back. The trip includes 5 miles of single-track. After three miles of roads, you get on single-track. Here, the route continues to climb, traversing around the west flank of Gray Butte. This stretch provides views of familiar landmarks like Black Butte, Green Ridge, and Three Sisters.
An exhilarating single-track descent off of Gray Butte into Skull Hollow highlights the excursion. The route dodges trees, banks past rocks, and swoops through swales. The trail leads the way, but it's up to you to negotiate its sandy corners, rocky sections of tread, and occasional steep drops (fun stuff). The trailhead is Skull Hollow Campground in the Crooked River National Grassland, about 15 miles northeast of Redmond."