Pair attached to an axle

Wiktionary Word definitions in Wiktionary
n. A wheel and axle combination. For example, it can refer to: the front and back bicycle wheels (with axles) sold as a ready-made set; or an axle and mounted left and right pair of railroad wheels.

Wikipedia Word definitions in Wikipedia
A wheelset is the wheel - axle assembly of a railroad car . The frame assembly beneath each end of a car, railcar or locomotive that holds the wheelsets is called the bogie (or truck in North America ). Most North American freight cars have two bogies with ...