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Shimano Alivio RD-M3100 9-Speed Rear Derailleur  SGS/Long Cage
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Shimano Alivio RD-M3100 9-Speed Rear Derailleur

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9 Speed Done Right

Shimano's Alivio 9-Speed Rear Derailleur uses trickle-down technology to offer consistent and crisp shifting performance. With the low profile SHADOW derailleur design you'll be able to ride harder with fewer derailleur issues overall. So whether you're searching for a replacement derailleur or are building up a new 9-speed bike, the Alivio rear derailleur is a great choice.


  • Adjustment barrel is easily accessible
  • Low profile SHADOW design
  • Total capacity: 45T
  • Max low sprocket: 36T, Min low sprocket: 32T

  • B-Stock - This product has one or more B-Stock units available. These units can be purchased at a discount (see option select). B-Stock units were returned from other customers and may have missing or damaged packaging materials. These units are otherwise as new. The full manufacturer warranty applies. Click Here for more information.

    Mfg PartNum: ERDM3100SGS 

    Ordered by Most Relevant First
    5 stars
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    1 stars
    Reviewed 4/14/2022
    by davidlansing
    Cycling Enthusiast
    Lansing, MI
    Value Rating
    Overall Rating
    2 of 2 customers found this review helpful.
    Best option for Shimano 9-speed SGS derailleur

    If you are still running a 9-speed Shimano drivetrain, this RD-M3100 is your best remaining option for a long cage rear derailleur. You can find used or new-old-stock higher lineage parts like Deore, SLX, or XT for your 9-speed drivetrain, but the increased cost and older technology of the legacy parts don't really justify the effort.

    This derailleur works just fine with older (and newer) 9-speed systems. It takes a maximum 36T rear sprocket, with a 45T Total Capacity spec between front and rear chainrings and sprockets, and it comes with an adjusting barrel.

    I bought 2 of these from BikeTiresDirect and installed one on my touring bike, pairing it with a Sram Centera 9-speed twist shifter. It works like a champ. The other is going on an old LX/XT Specialized Stumpjumper hardtail mountain bike, and I am sure that it will work similarly well.

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