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In addition to working with Shimano 11-speed drivetrains, this modified 11-49 cassette works with any 1x SRAM 11 speed rear derailleur and shifter. If you have an NX drivetrain, it drops right in! If you have XX1, X01, X1, or GX, you need a Shimano freehub driver, 11-42 cassette from SRAM, Shimano, or SunRace, and the GC49.  

The GC 49 is the latest addition to the legendary GC line and it's the biggest yet. The GC 49 cassette extender cog allows you to modify your 11 speed 11-42T cassette from SRAM to create an ultra-wide range 11T-49T cassette. To achieve the best shifting, the GCs are optimized for (Shimano) or (SRAM / SunRace) cassettes. This includes 18T cassette cog for optimal gearing in the smaller cogs.

You might ask why 49t rather than 50t, and the answer is simple:

  1. It allowed us to nearly double the number of shift gates from 4 on a 50t to 7 on a you get much faster shifting. With cogs this big, this is critical as you can be waiting nearly a half revolution of the crankset before you will see a shift with only 4 shift gates.
  2. SRAM 11 speed rear derailleurs can only handle 49t as a max cog size.
  3. The 49t is only 2% different than a 50t, which is so small it won't be noticed.



  • Compatible only with SRAM PG-1130 11 speed NX cassettes and SunRace 11-speed 11-42 cassettes listed on the GC tech page NOT compatible with any SRAM cassettes using the XD driver (10 tooth small cog).
  • Compatible with all 11-speed chains
    • Note that you likely need a longer chain than you currently have your bike. Chain length is critical with the 49T and must be set according to the instructions on the GC tech page.
    • Chain wear should be less than .5 when installing a new GC or chainring.
  • Compatible with all 1x SRAM 11-speed rear mountain derailleurs (NX, GX, X1, X01, XX1).  Not compatible with 2x systems from SRAM.
  • Also Compatible with Shimano 11 speed mountain derailleurs when using our Wolf Cage modification.
  • Caution: always check full suspension travel with the chain on the GC 49. Bleed air from rear shock and fully compress the rear suspension to check. Derailleur cage must not bottom out in forward rotation.
  • 18t cassette cog is included with the GC49. Remove the 17 and 19t cogs and replace them with the 18t.
  • These are specifically designed for use with SRAM cassettes. The clocking, or rotational orientation, between SRAM and Shimano cassettes are much different so optimal shifting cannot be achieved unless the design is optimized for each separately.


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    Tech Specs

    Weight: GC49 • 110g  | 18t cog • 22g
    Material: GC • 7075-T6 aluminum
    Made in the USA

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