West of Moab, the Poison Spider Trail is a 10 mile network of doubletrack and slickrock with some sandy steep climbs. Poison Spider Mesa forms one of the cliff features that is part of the Moab landscape northwest of town. The mesa is bordered on the east by Moab Valley and on the south by the Colorado River.
The trail climbs to the rim along with the sloping rock layers. The first few miles of trail must be retraced, but most of the travel time will be spent on a loop that reaches the rim. It has deservedly become of the most popular trails because it has great scenery. After some switchbacks that traffic is making rougher and a fairly flat stretch, a sandy canyon leads to some switchbacks about 2 miles into the trail. There are steep slickrock climbs, one sand hill may be difficult to climb.
Most mountain bike ride this as an out and back to the long sandy stretch since the trail beyond that leads back down to SR279 gets extremely technical.
To reach the mountain biking trailhead from Moab, head north on US191 for 1.5 miles to SR279 (aka Potash Road). Turn left heading southwest on SR279 for 6 miles and look for the trailhead on the right, just past the rock climbing zone.
From the trailhead, the route goes to Little Arch and back. The trail starts by climbing up onto the mesa on a rocky, cobbly road. After ascending several switchbacks, the trail hits a lengthy section of sand at mile 2.3. At the end of the sandy canyon, the trail goes up a series of rock steps to get atop the mesa proper (ignore the numerous spur roads along the way - the main route parallels the river). At about mile 5.1, the trail descends a hill. The bike route to Little Arch stays right (ignoring the road that takes off to the left). Head to the northeast and be particularly alert to trail markings at this point. At mile 5.7, you will reach the approach to Little Arch. The arch cannot be scene from the trail - you must park your bike and walk toward the river for 100 yards. The best route back is the same way you came. The route beyond the arch leading toward Moab is very treacherous.