SunTour Gran-Prix

SunTour Gran-Prix derailleur main image

The Suntour Gran-Prix introduced the slant parallelogram to the world. It is the most famous of the many brain-children of Nobuo Ozaki, SunTour’s legendary chief designer. The idea is brilliantly simple - as the pulley cage moves inwards, it also moves downwards, following the shape of the freewheel and maintaining a reasonably constant chain gap. Virtually every modern derailleur of any quality uses this design. The 1964 patent on this design (US patent # 3,364,762) allowed SunTour to gradually dominate the derailleur industry, until it ran out in 1984.

The SunTour Gran-Prix was also notable in a number of other ways.

It fits a Campagnolo hanger (and has an adjustment screw) - starting the Japanese move away from Huret (SunTour’s original choice) and Simplex (Shimano’s original preference). The hanger plate on this example is particularly unusual with two holes for drop-out bolts - but it has the tell-tale Campagnolo tag position.

The Gran-Prix is low-normal (‘Rapid Rise’ in Shimano-speak). And, in addition, it uses SunTour’s unique single spring design - the same spring operates the parallelogram and also tensions the chain. These last two features are a touch too mad for my tastes - and I have never found low normal gears to be very positive - whether they are the ancient, cheapo, SunTour Skitter or the ultra-modern, fantastically refined and expensive Shimano XTR.

Finally the Gran-Prix illustrates a problem with naming a product in an alien character set. Sometimes SunTour labelled the actual derailleur as a Gran-Prix, sometimes as a Grand-Prix, and, on at least one occassion they advertised it as a Grand Prix (without the hyphen) - all of which should be just enough to avoid having to pay royalties to the impishly charming Bernie Ecclestone.

  • Derailleur brands: SunTour
  • Categories: SunTour - the V story
  • Country: Japan
  • Date of introduction: 1964
  • Date of this example: unknown but before 1970 (the parallelogram plates and pulleys are stamped ‘Maeda Iron Works’ )
  • Model no.: unknown
  • Weight: 289g including hanger plate but excluding drop-out bolt(s?)
  • Maximum cog: 24 teeth?
  • Total capacity: 24 teeth?
  • Pulley centre to centre: 46mm
  • Index compatibility: friction
  • Chain width: 3/32”
  • Logic: low normal
  • B pivot: two pivots, front sprung and rear unsprung
  • Materials: steel parallelogram plates and pulley cage plates, bronze(?) knuckles (they are chromed but not magnetic)
SunTour Gran-Prix derailleur additional image 01

Browse associated documents.

US Patent # 3,364,762 - SunTour

US Patent # 3,364,762 - SunTour

US Patent 3,364,762 - SunTour Gran-Prix thumbnail

New Cycling 03/1966 - SunTour ad

New Cycling 03/1966 - SunTour ad

New Cycling March 1966 - SunTour advert thumbnail

New Cycling 09/1966 - SunTour ad

New Cycling 09/1966 - SunTour ad

New Cycling September 1966 - SunTour advert thumbnail

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