Meet a rare breed of devoted racer: Stacy Kohut, the world's fastest mountain biker on four wheels. Brought up in a drag racing family, as a grom Kohut rode full throttle into everything — an accident on a swingset in 1992 nearly ended all that. Today, Kohut credits those experiences for the athletic prowess needed to master the custom four-wheeled mountain bike of his own design. And as unique as his machine, Kohut is one of the most devout athletes to his sport.