Simplex SX500 CP
Main Photo
Category:  Rear Derailleurs
Name:  Simplex SX500 CP
Brand:  Simplex
Primary Group:  SX
Model:  SX500 CP
Years:  1975 - 1977
Country:  France
Weight:  176 grams (Spec),
this example without chaine guide: 163 actual !
Added By: tmundry67 on 01/27/22
Updated By: tmundry67 on 01/28/22
Additional Photos - click for full size
Simplex SX500 CPSimplex SX500 CPSimplex SX500 CPSimplex SX500 CPSimplex SX500 CPSimplex SX500 CPSimplex SX500 CPSimplex SX500 CP
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Outer Plate MarkingsSimplex (black on gold rectangular badge)Inner Plate MarkingsPrestige Simplex Super L.J. / Made in France / Brevete S.G.D.G.
MaterialAluminum Alloy; PlasticDesign CategoryInline parallelogram
Attachment Bolt SizeSimplex Special Bolt for threadless Simplex DropoutsCable Attachment Bolt Size8mm Wrench
Shifting SystemsFrictionCable AdjusterNo
Cage LengthShortMax Cog Size26
Max Chain Wrap28  
General Information
In 1975 Simplex introduced a wide product palette with respect to derailleurs, probably the broadest in their history. Only few years later this range was condensed significantly again. This is why some of the derailleurs presented in 1975 are very hard to find today and appear to be hardly existing just liek the presnetd example SX 500 CP. The concept and real demand of this derailleur range can be discussed especially as many models are very close to the others in design and composition with sometimes only single parts being exchanged or shared between low, mid and high class derailleurs. In fact, the product range differentiates between low range (SX Series), mid range (LJ Series) and top models (SLJ Series), with 13 models overall (!) in 2 or sometimes three versions/variants. E.g. There are 5 different SX models, each of them in a short and long cage version or sometimes in touring (= T) or road race (CP = course professionelle) design with differences in the pulley cage attachment to the parallelogram. The technical differences appear small except the changes in materials (effect on weight) and surface finish (e.g. zinc coated versus chromed steel or polished alloy). As well nearly all of the models were available with the hanger plate (or axle claw) for frames without threaded derailleur hanger and alternatively with the special Simplex bolt array originally designed for Simplex dropouts with threadless derailleur hangers (which however can also be fit into threaded hangers). The SX 500 CP Model discussed here is an extraordinarily rare model. Basically it shares a lot of the much more common LJ 4000, i.e. 2 plastic/Delrin knuckles and aluminum alloy parallelogram plates as well as alloy bolts. This results in an extremely low weight which is in a competitive range to other lightweights such as the Huret Jubilee and also comparable to Simplex' lightes model, the LJ 4000. Front and back plate as well as the pulley cage appear to be shared parts of the LJ 4000, the back plate labeled with "Prestige Simplex – Super L.J." The only characteristic differentiation from the LJ 4000 are the bolts which do not have any incised lettering and the lower knuckle and bolt which is slightly shorter and fixed with SX typical counter nut. I added a picture with a head to head of the SX 500 and LJ 4000 to illustrate. Per 1975 catalogue this model should also be available in Touring (T) version as well as with long cage (GT = grand touring). I have never seen any of them and the presented example is the only I have ever seen from the SX 500.
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Additional Resources
Resources:Reference & ChartsCatalogsExternal Resources
Component Groups
Primary Group NameBrandQuick InfoBrowse Group Components
SXSimplexView 5 Components
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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