Dirtbikes (also trail bikes) are off-road motorcycles that are lightweight and feature rugged suspension and knobby tires to get traction off the pavement. MX stands for motocross, the sport of all-terrain racing on outdoor circuits. Motocross is a contraction of motorcycle and cross country. The long-travel suspension on MX bikes enables incredible speed over even harsh off-road conditions and massive triple-jumps. Supercross is a variation of motocross that is raced on indoor or stadium circuits. SX got its name from an original event in Los Angeles during the 1970s that was called the Superbowl of Motocross.