“An easy dirt road through the Mojave desert region of Joshua Tree National Park with lots of the namesake Joshua Trees.”
— Lost Justpastnowhere
The dirt roads in the Queen Valley area offer a better way to experience the park than through the window of a car, provided of course that it isn't too hot and you've brought plenty of water.
There seem to be more Joshua trees at the western portion of this trail. You'll also have good views of the faraway Transverse Ranges mountains towards the west guarding the outskirts of Los Angeles.
Just beyond the western terminus of this dirt road is the parking area for Barker Dam. The eastern terminus is at the Desert Queen Mine parking area, but you'll have to leave your bike to visit the mine as it requires a trip on singletrack and of course bikes are not allowed on singletrack in Joshua Tree National Park.