The Shimano Positron 400 (DG-300) was a racy little number, with a dropped parallelogram, an aluminium rear knuckle and a short 46mm pulley cage. It had something of the look of the Shimano 600 (or rather its steel intensive brother - the Shimano 400).

However the geometry was noticeably different, with a distinct backwards slant on the rear knuckle - so that the rear sprung pivot is behind the parallelogram - the weight was even more distinctively different - and then there was that despicable piano wire...

Close, Colonel, but no cigar.

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1. •Brand: Shimano
   

2. •My category: Shimano - Positron indexing insanity
   

3. •Country: Japan
   

4. •Date of introduction: 1977?
   

5. •Date of this example: unknown (no two letter date code)
   

6. •Model no: DG-300 or P240
   

7. •Weight: 329g including hanger plate
   

8. •Maximum cog: 28 teeth (Sutherlands 6th edition)
   

9. •Total capacity: 28 teeth (Sutherlands 6th edition)
   

10. •Pulley centre to centre: 46mm
    

11. •Index compatibility: 5 speed
    

12. •Chain width: 3/32”
    

13. •Logic: operated by piano-wire cable with no ‘normal’ position
    

14. •Pivots: two sprung pivots
    

15. •Material: largely steel, with an aluminium rear knuckle
    

0020/A