Located southeast of Crested Butte, the Trail #400 is a singletrack that climbs for the sky near Crystal Peak at 12,700'. The trail leads up the East Brush Creek drainage towards the many huts near Pearl Pass. The 400 also provides access to the beginning of the Double Top Trail (#405).
To reach the mountain biking trailhead from CB, follow SR135 south for two miles. Turn left heading east onto Brush Creek Road (FS738). After fjording West Brush Creek, continue and park near the intersection with East Brush Creek (FS738B). Continue riding up FS738B which turns into Trail #400.
Overall, East Brush Creek / Trail 400 is the 44th most popular mountain bike trail of all 175 mountain biking rides in Colorado.