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Simplex Juy 51
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Category:  Rear Derailleurs
Name:  Simplex Juy 51
Brand:  Simplex
Model:  Juy 51
Years:  1951 - ?
Country:  France
Weight:  425.2 grams (Spec)
Added By: JFischer on 06/04/09
Updated By: peterbman on 05/15/15
Additional Photos - click for full size
Simplex Juy 51Simplex Juy 51Simplex Juy 51Simplex Juy 51Simplex Juy 51Simplex Juy 51Simplex Juy 51Simplex Juy 51
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Outer Plate MarkingsSimplex Made in FranceInner Plate Markings
MaterialSteelDesign Category
Attachment Bolt SizeClawCable Attachment Bolt Size
Shifting SystemsFrictionCable AdjusterNo
Cage LengthShortMax Cog Size26
Max Chain Wrap20T  
General Information

Can be used for up to 4-speeds with a 1/8" chain, or 5 speeds using a 3/32" chain.  One of the first derailleurs with automatic "chain tension" adjustment.  Could be attached with the claw adapter, or directly to Simplex dropouts.

Kurt Sperry/CR: "This is essentially an elaboration of the TdF with a couple of significant differences: firstly, the pulley cage is non-axial with the lower pivot to optimize the jockey pulley geometry relative to the FW cogs across the shifting range as became normal practice for derailleurs, and secondly the Juy 51 has a second cable that is clamped to the main shifting cable that attaches just before the chainstay cable stop. The second cable runs through the housing between the chainstay stop and the derailleur stop together with the main cable to the 'chainette' and appears to adjust the preload on the lower pivot spring by rotating the spring stop as the gear cable goes through its travel. ..."
Quality:Rarity:
 
 
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Brand Information(click to expand)

Known for their black plastic (Delrin) derailleurs during the "bike boom" of the 1970's, they were at the forefront of innovation over the years, producing such highly regarded items as the Super LJ derailleurs, Retrofriction shifters, and very popular line of seat posts.

 
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