SunTour aRX GT (4500)

SunTour aRX GT derailleur (4500) main image

In response to Shimano’s radical 600 AX aerodynamic groupset, SunTour transmuted the Vx series into the aRX series (the name being something to do with aero and x). At first this seemed a brilliant move - the aRX 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.

But SunTour’s problems with controlling prices as the Yen sky rocketed were starting to tell. The Vx was all aluminium, the aRX had significant steel parts. And there were quality niggles - the aRx’s cable clamp bolt wasn’t quite of the quality it should have been and had an irritating tendency to strip.

The design also had its problems. Feeding the internal cable routing, acceptable on a deluxe low-volume product like the Cyclone, seemed a bind on the mass market aRX (I imagine manufacturers were particularly pained by this). I also suspect that SunTour had subtly changed its geometry - the aRx never seemed to shift quite as well as the older models.

Finally, 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.

Before the aRX appeared, the Vx series was still strongly out-selling the Shimano 600 series. A few years later the Shimano New 600 EX (6207) was comfortably out-selling the SunTour aRX series. I personally used numbers of V’s and Vx’s, but shifted to Shimano at this time.

The aRX GT is the long arm version. Because of the steel pulley cage it weighs in at a fairly meaty 250g.

  • Derailleur brands: SunTour
  • Categories: SunTour - the V story
  • Country: Japan
  • Date of introduction: 1981
  • Date of this example: 1984 (two letter date code is AB)
  • Model no.: 4500
  • Weight: 250g
  • Maximum cog: 34 teeth (Source: SunTour assuming 29mm dropout)
  • Total capacity: 32 teeth (Source: SunTour assuming 29mm dropout)
  • Pulley centre to centre: 67mm
  • Index compatibility: friction
  • Chain width: 3/32”
  • Logic: top normal
  • B pivot: unsprung
  • P pivot: sprung
  • Materials: aluminium knuckles and outer parallelogram plate, steel inner parallelogram plate and pulley cage plates.