An axle is a central shaft for a rotating wheel or gear. Axles
may be fixed to the wheels rotating with them and bearings or bushings are
provided at the mounting points where the axle is supported. When an axle is fixed to its surroundings
with the wheels rotating around the axle, a bearing or bushing sits inside the
hole in the wheel to allow the wheel or gear to rotate around the axle.
Sometimes, especially on scooters, pocket bikes and dirt bikes, the latter type
is referred to as a spindle.