A mountain bike or mountain bicycle (abbreviated Mtn Bike, MTB; or ATB, for all-terrain bicycle) is a bicycle designed for off-road cycling. Mountain bikes share similarities with other bikes, but incorporate features designed to enhance durability and performance in rough terrain. These typically include suspension on the frame and fork, large knobby tires, more durable heavy duty wheels, more powerful brakes, and lower gear ratios needed for steep grades with poor traction.