In response to Shimano’s radical Dura-Ace AX aerodynamic groupset, SunTour transmuted the Cyclone series into the Cyclone Mark-II series. At first this seemed a brilliant move - the Cyclone Mark-II series looked smooth and aerodynamic and modern, but was simple and practical unlike Shimano’s dangerous radicalism. Natty modern touches included allen key pulley bolts and an allen key cable clamp bolt.

However, by acknowledging the aerodynamic trend, SunTour had granted Shimano the status of ‘radical technology leader’ and taken up the role of ‘sensible conservative follower’. With the exchange of these roles the SunTour brand lost some sparkle that it never got back.

And ‘sparkle’ is the one issue that I have with the Cyclone Mark-II GT. The previous generation of Cyclones were highly sculpted, intricately detailed and lustrously anodised. They looked considerably more desirable than the lower price V series derailleurs. The Cyclone Mark-II GT deliberately used plain forms (the tyranny of aerodynamics), was anodised a slightly grey shade of silver, had printed rather than embossed branding and looked extremely similar to the lower price aRX series.

At 173g the SunTour Cyclone Mark-II GT is one of the lightest touring derailleurs in this collection. It is an engineering tour-de-force, but it hides its light under a curiously anonymous bushel.


  1. Brand: SunTour

  2. My category: SunTour - the Cyclone story

  3. Country: Japan

  4. Date of introduction: 1981

  5. Date of this example: 1982 (two letter date code is YC)

  6. Model no: 3700

  7. Weight: 173g

  8. Maximum cog: 34 teeth (Source: SunTour)

  9. Total capacity: 34 teeth (Source: SunTour)

  10. Pulley centre to centre: 66mm

  11. Index compatibility: friction

  12. Chain width: 3/32”

  13. Logic: top normal

  14. Pivots: two pivots, front sprung and rear unsprung

  15. Material: aluminium


SunTour Cyclone Mark-II GT (3700)