West of Aspen, the Snowmass Mountain ski area has an extensive network of purpose-built mountain bike trails. Some of the ski area lifts and gondola do carry bikes from mid-June through August, but the days and hours of operation vary. As of July 2011, the Elk Camp Gondola carries bikes daily starting at 10am, and the Elk Camp chairlift carries bikes to the summit Friday through Sunday to access the new Summit Trail.
To reach the Snowmass trailhead from downtown Aspen, head west on SR82 for 6 miles. Turn left on Brush Creek Road for 4.5 miles to the Snowmass Village Mall base area where parking is available and there is a bus station which connects with Aspen.
If going downhill is not your thing, you can try cutting across the mountain on the rocky, rooty Government Trail.
Overall, Snowmass Mountain is the 135th most popular mountain bike trail of all 176 mountain biking rides in Colorado.