From VisitMT.com:
The area around West Yellowstone boasts a wealth of great mountain biking. One of best-advanced rides is the 14-mile Lionhead Loop. Meadows brimming with wildflowers in summer, stunning views down into Hegben Lake make the 2,500 feet of climbing worthwhile.
The trailhead is located 7 miles east of West Yellowstone off of Highway 20. Turn right onto Denny Creek Road and drive 1.5 miles to the trailhead. The trail begins as an ATV trail and it is a good stiff climb for about 3 miles along Trail #217 where there is a fantastic view down into Hegben Lake. Go past a gate in the road and then turn left onto another small two track past meadows of wildflowers and the face of Lionhead Mountain looming to the west. Another 2.5 miles of climbing will bring you up to 8750 feet and around the shoulder of Lionhead Mountain. You are near the Continental Divide and the Idaho border. Then it is a fast downhill on Trail #114. This is followed by a couple of lefts onto forest roads, before coming out onto Highway 20. Turn left (east) onto Highway 20 and head back to Denny Creek Road.
