Amasa Back is one of the top three recommended trails in Moab. I love it for the views and the good workout that it can give you. Otherwise, it's a beat up rocky/technical double track with a very technical/many a hike a bike moments downhill (called Jackson's trail) that provides more stunning views of the Colorado River. Many (most) do Amasa Back as an out 'n back, leaving off Jackson's trail. Don't get me wrong. This is a great trail but I like Poison Spider Mesa linked with the Portal Trail way better.
Ride Type: Loop utilizing rocky double track to top and extreme technical singletrack downhill
Distance: 8.92 mi
Elevation Gain: 1979 ft
Time: 1.75-3hrs
Season: Spring & Fall to avoid extreme heat
Recommended Map: Moab West by Latitude 40
(includes Amasa Back, Poison Spider Mesa, Gemini Bridges, Hurrah Pass, Jackson's, Sovereign and many more)