Shimano launched the MJ with much fanfare as a derailleur specifically designed for children’s bikes. The cynics amongst us noted the similarity to the Shimano Tourney TY30 and wondered whether the ‘child friendly design’ went any further than the rather alluring ‘holographic’ nameplate.

I can’t remember if Shimano claimed any mechanical differences between the MJ and the Tourney - but the MJ did not seem to be a specifically ‘children’s design’ - unlike the Shimano Lark Mini (DD400) or the SunTour Love.

• Derailleur brands: Shimano
• Categories: Shimano - weirdness
• Themes: Small wheels on my wagon
• Country: Japan, manufactured in Singapore
• Date of introduction: 1993
• Date of this example: 1993 (two letter date code is RD - yes, really)
• Model no.: MJ10 SS
• Weight: 308g including hanger plate
• Maximum cog: 28 teeth (Sutherland’s 6th edition)
• Total capacity: 28 teeth (Sutherland’s 6th edition)
• Pulley centre to centre: 55mm
• Index compatibility: 6 speed (Sutherland’s 6th edition)
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: steel (the plastic is decorative!)