The Alivio RD-M3100-SGS 9-speed rear derailleur( Shimano , part number ERDM3100SGS) is designed for 9-speed Shimano MTB drivetrains. Featuring SHADOW RD ‘Shimano ’ technology and a long SGS cage, it offers smooth, precise and quiet operation, whilst boasting a low-profile design that minimises the risk of contact with obstacles or the frame stays.

With a total capacity of 45 teeth and the option to use a cassette with a large sprocket of up to 36 teeth, the RD-M3100-SGS is a versatile solution for compatible 1x9, 2x9 and 3x9 MTB drivetrains.

Shimano Alivio 9-speed rear derailleur with long cage

The Shimano Alivio RD-M3100-SGS is designed for cyclists looking for a reliable rear derailleur for recreational, touring or competitive mountain biking.

Its SGS long cage allows it to handle a wide range of sprocket sizes and is compatible with single, double or triple chainring set-ups. Shimano specifies a total capacity of 45 teeth, with a maximum rear sprocket size of 36 teeth.

The RD-M3100-SGS is designed to work with a Shimano HG 9-speed chain and is intended for 9-speed rear drivetrains.

Shimano SHADOW RD technology

The Alivio M3100 rear derailleur features SHIMANO SHADOW RD technology. This low-profile design reduces the derailleur’s protrusion, thereby minimising the risk of contact with the rear dropout during technical sections.

Combined with a single-tension construction, this design ensures smooth and quiet drivetrain operation. It is particularly well-suited to the demands of mountain biking.

A versatile 9-speed drivetrain

The RD-M3100-SGS can be used in 2x9 and 3x9 set-ups, and is also suitable for 1x9 set-ups provided the other drivetrain components are compatible.

For a double or triple drivetrain, Shimano specifies a maximum front chainring difference of 22 teeth. The largest rear sprocket can be up to 36 teeth, whilst the smallest sprocket must fall within the range specified by the derailleur’s specifications.

This versatility makes it an attractive choice for replacing a worn Alivio derailleur or refurbishing a 9-speed MTB drivetrain.

Technical specifications

• Brand: Shimano
• Groupset: Alivio M3100
• Model: RD-M3100-SGS
• Manufacturer’s part number: ERDM3100SGS
• Type: MTB rear derailleur
• Number of speeds: 9
• Chape: long SGS
• Technology: Shimano SHADOW RD
• Compatible chain: Shimano HG 9-speed
• Maximum rear sprocket size: 36 teeth
• Minimum large sprocket: 32 teeth
• Maximum small sprocket: 12 teeth
• Minimum small sprocket: 11 teeth
• Total capacity: 45 teeth
• Maximum difference between chainrings: 22 teeth
• Adjustment: integrated adjustment barrel
• Use: Mountain bike / MTB
• Colour: standard colour
• EAN: 4550170621155

The main features are confirmed by the specifications Shimano and the manufacturer’s data available for the RD-M3100-SGS.

Which drivetrain should you choose the Shimano RD-M3100-SGS for?

The RD-M3100-SGS is particularly well-suited to the following set-ups:

• 1x9: a single chainring at the front and a compatible 9-speed cassette.
• 2x9: two chainrings at the front and a 9-speed cassette.
• 3x9: three chainrings at the front and a 9-speed cassette.

For a 2x9 or 3x9 configuration, you should check that the total capacity required does not exceed the 45 teeth specified by Shimano.

Installation and adjustment

To replace the RD-M3100-SGS, you must attach the derailleur to the derailleur hanger on the frame, then connect and adjust the control cable.

Precise adjustment of the limit screws, cable tension and the derailleur’s position relative to the cassette is essential to achieve fast and precise gear changes.

Before fitting, it is also advisable to check the condition of the derailleur hanger, the chain and the cassette. A heavily worn chain or a slightly bent derailleur hanger can impair the performance of a new derailleur.