Internal forces, those between components of the bike and rider system, are mostly caused by the rider or by friction. In addition to pedaling, the rider can apply torques between the steering mechanism (front fork, handlebars, front wheel, etc.) and rear frame, and between the rider and the rear frame. Friction exists between any parts that move against each other: in the drive train, between the steering mechanism and the rear frame, etc. In addition to brakes, which create friction between rotating wheels and non-rotating frame parts, many bikes have front and rear suspensions, and some motorcycles have a steering damper to dissipate undesirable kinetic energy.[14] On bikes with rear suspensions, feedback between the drive train and the suspension is an issue designers attempt to handle with various linkage configurations and dampers. n a motor vehicle, the term powertrain or powerplant refers to the group of components that generate power and deliver it to the road surface, water, or air. This includes the engine, transmission, drive shafts, differentials, and the final drive (drive wheels, continuous track as in tanks or Caterpillar tractors, propeller, etc.). Sometimes "powertrain" is used to refer to simply the engine and transmission, including the other components only if they are integral to the transmission. In a carriage or wagon, running gear designates the wheels and axles in distinction from the body. A motor vehicle's driveline or drivetrain consists of the parts of the powertrain excluding the engine and transmission. It is the portion of a vehicle, after the transmission, that changes depending on whether a vehicle is front-wheel, rear-wheel, or four-wheel drive, or less-common six-wheel or eight-w eel drive. In a wider sense, the power-train includes all of its components used to transform stored (chemical, solar, nuclear, kinetic, potential, etc.) energy into kinetic energy for propulsion purposes. This includes the utilization of multiple power sources and nonwheel-based vehicles. A steering damper, steering stabiliser or sprint damper is a damping device designed to inhibit an undesirable, uncontrolled movement or oscillation of a vehicle steering mechanism, a phenomenon known in motorcycling as wobble, or in extreme cases, a tank-slapper. Modern motorbikes are unlikely to exhibit this behaviour in daily use thanks in part to better dampers and due to their very stiff front ends and other general improvements in design and tyre technology. Sport bikes have a short wheelbase and an aggressive steering geometry to provide the ability to make very quick changes in direction. This has the harmful side-effect of making the bike less stable, more prone to feedback from uneven road surfaces, and more difficult to control.[1] In addition, their light weight and powerful engine can cause frequent wheelies. If the front wheel significantly deviates from the direction of travel when it touches down, it may cause an unwanted wobble. Steering dampers are factory installed on some high-end sport motorcycles and fitted to most contemporary racing bikes to counter these behaviours. Steering dampers are also mounted to off-road motorcycles such as motocross bikes.[2] A damper helps keep the bike tracking straight over difficult terrain such as ruts, rocks, and sand, and also smooths out jolts through the handlebars at the end of jumps. They also reduce arm fatigue by reducing the effort to control the handlebars.