US Patent 11852471 Rear derailleur and cassette pre-checking device

A derailleur hanger alignment pre-checking device, for use on a bicycle having a cassette comprising multiple sprockets and a rear derailleur having a derailleur cage, includes an elongated body having a longitudinal axis and an elongated planar surface disposed substantially parallel to the longitudinal axis, and including a handle portion and a hanger portion. The hanger portion includes a slot cavity having an arcuate rear wall, the slot cavity being configured to receive a portion of a sprocket of the cassette. The slot cavity and planar surface are configured so that when a sprocket is received in the slot cavity the planar surface will be positioned facing a planar surface of the derailleur cage.