SunTour S-1 (S120)

SunTour S-1 derailleur (S120) main image

Ever the inventors, SunTour introduced the radical S-1 design just when its fortunes were at their lowest ebb. It was an updated version of the 1938 Nivex and 1955 Altenburger designs, mounting on a braze-on under the chainstay and using a horizontal parallelogram. SunTour went one step further than these hallowed forebears and incorporated the rotating cam indexing system from the Bridgestone Klimatic.

Designed for commuting bikes, it all looked quite well thought out - but a SunTour system that demanded special unique frame fittings was never going to catch on a world in which Shimano was now totally dominant.

This example is a short pulley cage S120 version.

  • Derailleur brands: SunTour
  • Categories: SunTour - indexing insanity
  • Country: Japan
  • Date of introduction: 1992
  • Date of this example: 1992 (two letter date code is ID)
  • Model no.: S120
  • Weight: 322g excluding braze-on fitting
  • Maximum cog: 28 teeth?
  • Total capacity: 24 teeth?
  • Pulley centre to centre: 42mm
  • Index compatibility: 7 speed
  • Chain width: 3/32”
  • Materials: aluminium front knuckle, plastic rear knuckle, steel parallelogram plates and pulley cage plates
SunTour S-1 derailleur (S120) additional image 01

Browse associated documents.

US Patent # 5,380,253 - SunTour

US Patent # 5,380,253 - SunTour

US Patent 5,380,253 - SunTour S-1 thumbnail
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