This trail begins at the old pumice mine on Highway 4, just west from the East fork parking area at the top of the hill. You can park there and ride up the highway for a half mile, or park at the top. The ride is best done as a shuttle from the top down, or half way from the Jemez Falls campground.
You enter the old access road to the pumice mine and follow the singletrack across the top to the north side. From here it becomes fast and wide singletrack for a mile, then crosses over onto the narrow singletrack on the right for the descent down to the middle parking area on highway 4 at the second crossing of the East Fork of the Jemez River.
Stay to the right at all trail forks for the best ride to the falls. When you cross Hwy 4 the trail resumes on the opposite side and becomes more technical as it descends to the river. There is a new bridge across the river as of 2014. After this you climb up to the parking lot for Jemez Falls, and the trail resumes on the other side of the parking lot. There are bathrooms here. A water tap might be available in the summer, but don't count on it.
Once on the other side the trail has a short steep climb, then begins descending in earnest. Pretty soon the trail will become a black diamond-expert only ride from this point down to Battleship Rock picnic area on Highway 4 again. About half way down this section you'll come to the Macaulay warm springs, nice place to soak your feet with fantail guppies. Overall, this is a nice and challenging ride that covers several climate zones on the way down.
This trail is often ridden downhill with a shuttle. However, it is quite practical to ride as an up-and-back from Battleship Rock. Parts will need to be hiked, but it is a great opportunity to scope out the tough sections that will be ridden on the way back down.