Biking -- Cycling is allowed on the 1,000 miles of dirt and paved roads used by motor vehicles in the park, but not on hiking trails or anywhere else. Weather conditions between May and October make bicycling at the lower elevations dangerous at times other than early morning.
There are no bike rentals available in the park, and given the park's isolation, the only practical option is to bring your own. You'll need a pretty rugged mountain bike to do most of these routes.
Good choices are Racetrack (28 miles one-way), Greenwater Valley (30 miles one-way, mainly level), Cottonwood Canyon (20 miles one-way), and West Side Road (40 miles one-way, fairly level with some washboard sections). Artists Drive is 9 miles long and paved, with some steep uphill stretches. Other favorites include Titus Canyon (28 miles on a one-way hilly road -- it has some very difficult uphill and downhill stretches) and Twenty-Mule Team Canyon Road (a one-way 2 3/4-mile graded gravel road through colorful badlands).
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.