With the Shimano RS (RS12) the already venerable Skylark design took a couple of small steps forward. The cable clamp was mounted on a Centeron lever, allowing the derailleur to automatically compensate for the need to overshift. Perhaps more significantly the Centeron lever acted on the outer parallelogram plate - changing the geometry of the gear, as previously the cable clamp was attached to the front knuckle.

Despite these changes, the RS is a cheap, basic, tidy, design that is clearly a Shimano Skylark underneath.

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1. •Brand: Shimano
   

2. •My category: Shimano - from Skylark to world domination
   

3. •Country: Japan
   

4. •Date of introduction: 1981?
   

5. •Date of this example: 1981 (two letter code FB)
   

6. •Model no: RS12 (chrome) or RS11 (zinc)
   

7. •Weight: 290g including hanger plate
   

8. •Maximum cog: 28 teeth
   

9. •Total capacity: 28 teeth
   

10. •Pulley centre to centre: 54mm
    

11. •Index compatibility: friction
    

12. •Chain width: 3/32”
    

13. •Logic: top normal
    

14. •Pivots: two sprung pivots
    

15. •Material: steel
    

0196/F