There are about 55 miles of well-maintained, endlessly beautiful Carriage Roads on Mount Desert Island for hiking, horseback riding, and bicycling. No motor vehicles are allowed on these hard packed, all weather roads. You'll definitely want to consult a trailmap which is available in the Campground Store. While a Cross or Mountain Bike is best for the Carriage Roads, there really aren't any trails on the island for Mountain Bikers.
All hiking trails are for foot traffic only.
The free Explorer bus has bike carriers to transport your bike from either the Campground or Bike Rental Store to the Carriage Trails if your car isn't equiped with a bike carrier.