Sugarloaf bike park manager Adam Craig jumps his bike July 23 while testing a jump built by trail crew members at the resort's bike park in Carrabassett Valley. In all, Maine has nearly 600 miles of mountain bike trails documented by MTB Project, an online crowd-sourced mountain bike guide. AdvertisementAnd as mountain parks have popped up, so have lift-served bike parks. Dunfee, a seasoned mountain biker and skier, believes lift-served mountain bike parks have loads of potential here. Lift-served mountain bike parks grew out of a desire to extend the usefulness of ski resorts, and transition to a profitable year-round season.