There’s something about French touring derailleurs after about 1960. Just one look at this Simplex SJ810 GT is enough to fill me with a crushing sense of despair. I can almost hear the chain hysterically clattering on the inaccurately cut teeth of the wide ratio Maillard freewheel as the SJ810 GT pathetically attempts to find bottom gear. I can almost see the bemused expression on the face of the owner of a Peugeot tandem as I attempt to invent a reason why a seemingly rational company like Peugeot had chosen to fit his relatively demanding machine with a poorly constructed derailleur with plastic parallelogram plates.

At heart the SJ810 GT was a Simplex Prestige with a long pulley cage - not a very promising foundation. And all that lack of promise was fully borne out - the SJ810 GT was heavy, unreliable and changed gear particularly poorly.

Even Edith Piaf would have regretted producing this dog.

• Derailleur brands: Simplex
• Categories: Simplex - touring terrors
• Country: France
• Date of introduction: 1975?
• Date of this example: unknown (rear knuckle stamped ‘D51’)
• Model no.: SJ810 GT
• Weight: 327g including hanger plate
• Maximum cog: 36 teeth (Sutherland’s 6th edition)
• Total capacity: 39 teeth (Sutherland’s 6th edition)
• Pulley centre to centre: 75mm
• Index compatibility: friction
• Chain width: 3/32”
• Logic: top normal
• B pivot: sprung
• P pivot: sprung
• Materials: plastic parallelogram plates and front knuckle, steel pulley cage plates and parallelogram stiffening plates, aluminium rear knuckle