The entire dunefield and most of the park and preserve's mountain trails are within federally designated wilderness, where mechanized equipment is not permitted.
While regular bicycling and mountain biking options are very limited, fat bikes (mountain bikes with extra wide tires for sand) are permitted on the Medano Pass Primitive Road, a challenging road with extended sections of sand, creek crossings, and rocks. The road is open to fat biking both for day use and for overnight camping in Medano Canyon. However, these bikes are not permited on State Highway 150, so plan to transport the bikes into the park inorder to access the primitive road where they are allowed.
You will be sharing the single lane road with 4WD vehicles, some traveling at higher speeds in order to make it through sandy sections. For your safety, listen and watch carefully for vehicles as you ride.