Simplex LJ4000 CP (version 3)
Main Photo
Category:  Rear Derailleurs
Name:  Simplex LJ4000 CP (version 3)
Brand:  Simplex
Model:  LJ4000 CP
Years:  1985 - 1990
Country:  France
Weight:  181 grams (Spec)
Added By: JFischer on 12/01/09
Updated By: peterbman on 03/13/16
Additional Photos - click for full size
Simplex LJ4000 CP (version 3)Simplex LJ4000 CP (version 3)
Outer Plate MarkingsSimplexInner Plate MarkingsSimplex Super LJ
MaterialAluminum Alloy; PlasticDesign Category
Attachment Bolt SizeCable Attachment Bolt Size
Shifting SystemsFrictionCable AdjusterNo
Cage LengthMediumMax Cog Size30
Max Chain Wrap30T  
General Information
Simplex LJ 4000 rear derailleur. Design is identical to the SLJ model, but upper and lower pivots are made with Delrin (Simplex's miracle plastic...), instead of aluminum.. Although the inner plate has a "Simplex Super LJ" marking (probably because this specific part was produced in first place for the SLJ derailleur), the model does not belong to the SLJ series.  This to be a photo of the T model (medium cage?) while the CP model appears to be a shorter cage version with smaller chain wrap and max cog size. There was also a Long Cage version which was known as the 4000 GT.  Very close inspection of the jockey cage is needed to distinguish the CP from T models.
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Additional Resources
Resources:Reference & ChartsCatalogsExternal Resources
Component VariationsView Detailed List  Manage Variations
Variations of Component exist (Component is 1 of 4)BrandGroup
Gipiemme Dual SprintGipiemmeDual Sprint
Simplex LJ4000 CP (version 1)Simplex
Simplex LJ4000 T (version 3)Simplex
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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