Simplex SX300 T
Main Photo
Category:  Rear Derailleurs
Name:  Simplex SX300 T
Brand:  Simplex
Primary Group:  SX
Model:  SX 300 T
Years:  1975 - 1977
Country:  France
Weight:  279 grams (Actual),
for version with direct attachment, with hanger: 292g
Added By: tmundry67 on 01/26/22
Updated By: tmundry67 on 01/28/22
Additional Photos - click for full size
Simplex SX300 TSimplex SX300 TSimplex SX300 TSimplex SX300 TSimplex SX300 TSimplex SX300 TSimplex SX300 T
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Outer Plate MarkingsSimplexInner Plate MarkingsSimplex / Brevete / S.G.D.G. / Made in France
MaterialPlastic; SteelDesign CategoryInline parallelogram
Attachment Bolt SizeSimplex Special Bolt for threadless Simplex DropoutsCable Attachment Bolt Size8mm Wrench
Shifting SystemsFrictionCable AdjusterNo
Cage LengthShortMax Cog Size30
Max Chain Wrap30  
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 like the SX 300. The concept and real demand of this enormous derailleur range can be questioned 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 300 T derailleur discussed here is a very rare model, in principal identical in design with the SX 100, however with a different front plate and chrome plated pully cage and some of the screws instead of the zinc coated parts with lower range models. The performance though is not different at all and it is relatively heavy in weight. One can identify this model by the red plastic rods in the allen key holes of the bolts (similar to the earlier prestige criterium AR637 of the early 1970s). In the 1975 catalogue you can at least see these plastic stoppers in the exploded view however not in the assembled aspect. I purchased this part on eBay France and so far it is the only specimen I have ever seen from the SX 300 model. The displayed example is for direct atatchment to derailleur hangers with the Simplex frame attachment.
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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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