With the Scrambler, SunTour introduced yet another mid-end indexing mechanism. This is a system based on an indexed lever, with the rear derailleur merely centred with a single adjusting screw, and with a ‘Light Action’ type spring built into the cable clamp mount. It is possibly the fourth indexing system Suntour introduced within a decade - not a good idea.
Heavy, ugly and not particularly cheap, no one was very interested.
But three features catch my eye:
- The pulley cage plates have a ninja/sci-fi look.
- It has an unusually large, 12 tooth, guide pulley.
- The centre of the guide pulley is offset from the p-pivot by a tiny amount - echoing a geometry that SRAM would later use on their ESP designs.
I think that this particular example is a early version with the following traits:
- The knuckles are grey.
- The main Allen bolts are chrome.
- The writing on the outer parallelogram plate is black on silver.
- The pulley wheels are black.
- Derailleur brands: SunTour
- Categories: SunTour - indexing insanity
- Country: Japan
- Date of introduction: 1985?
- Date of this example: 1985 (two letter date code is BH)
- Model no.: SR21
- Weight: 328g
- Maximum cog: 32 teeth?
- Total capacity: 34 teeth?
- Pulley centre to centre: 65mm
- Index compatibility: 5 speed?
- Chain width: 3/32”
- Logic: top normal
- B pivot: unsprung
- P pivot: sprung
- Materials: aluminium knuckles, steel parallelogram plates and pulley cage plates
