West of Grand Junction and Fruita, the Rabbit Valley Recreation Management Area has miles of trails to explore. The trails vary from buff singletrack with some sandy or rocky sections to packed/sandy double track. In the eastern half of Rabbit Valley, there is the popular Rim Trail (aka East Rim Trail) which has been pretty beat up in the past couple years from motorcycles.
To reach mountain biking at the Rim Trail trailhead from Grand Junction, head west on US70 to Exit #2. Head south on access road to the first intersection. Turn left for about 0.25 miles to the trailhead parking area.
Start riding south on Trail #3 to the Rim Trail (Trail #8).
Overall, Rim Trail is the 115th most popular mountain bike trail of all 175 mountain biking rides in Colorado.