Skull

The bottom section of Skull was recently reclaimed, the trail is now shorter.
If riding from town, the grind up 110 to the Little Rainbow trailhead can be monotonous. Ride into the new parking lot along CR 110, on the west side. Access the Spartan Connector on the south end of the parking lot. Turn left where it meets Spartan West. Cross CR110 and start Spartan East. After the first arroyo turn right, up Skull. It's a steady climb but not overly steep or technical. Watch for loose rocks and sandy corners. Once you hit Little Rainbow, you can turn right to go a short distance to the CR110 trailhead and further up to Double Rainbow, or Spartan West. Otherwise, turn left and take Little Rainbow over to Lost, Dead Bird, or Race Track.
Give Skull a try downhill too. You can see for a long ways and can really open it up, until you get to Spartan East.
Be careful of loose rocks in the corners.