A mountain bike or mountain bicycle (abbreviated Mtn Bike or MTB 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 a front or full suspension, large knobby tires, more durable wheels, more powerful brakes, and lower gear ratios for climbing steep grades. Mountain bikes are typically ridden on mountain trails, single track, fire roads, and other unpaved surfaces. This type of terrain commonly has rocks, roots, loose dirt, and steep grades. Many trails have additional TTF's (Technical Trail Features) such as log piles, log rides, rock gardens, skinnier, gap jumps, and wall-rides. Mountain bikes are built to handle these types of terrain and features. The heavy-duty construction combined with stronger rims and wider tires has also made this style of bicycle popular with urban riders and couriers who must navigate through potholes and over curbs.
Since the development of the sport in the 1970s many new sub types of mountain biking have developed, such as cross-country (XC), all-day endurance, free-ride, downhill, and a variety of track and slalom types. Each of these place different demands on the bike requiring different designs for optimal performance. MTB development has led to an increase in suspension travel, now often up to 8 inches (200 mm), and gearing up to 27 speeds, to facilitate both climbing and rapid descents. Advancements in gearing have also led to a "1x" (pronounced "one-by") trend, simplifying the gearing to one chaining in the front, and a cassette at the rear, typically with 9 - 11 sprockets.