The Shimano Deore XT RD-M8120-SGS is a 12 speed rear derailleur for 2x drivetrains with a 10-45T cassette. SHADOW RD+ and a cage bumper keep the drivetrain quiet.

What it's for

The rear derailleur for a Shimano 2x12 mountain bike drivetrain with a 36-26T double crank.

How it works

SHIMANO SHADOW RD+: a stabilizer in the derailleur that holds chain tension. It reduces chain slap and dropped chains.

HYPERGLIDE+: tooth and chain shapes that let you keep pedaling while you shift, up or down the cassette.

13T pulleys improve efficiency and chain management.

Bump Stopper: a bumper on the pulley cage quiets chain noise, and tension is lower in the low gear.

Compatibility

• Cassette: Shimano 12 speed, 10-45T
• Crank: front double, 36-26T
• Chain: Shimano 12 speed HYPERGLIDE+
• Does not fit: 10-51T cassettes. Use RD-M8100-SGS for those

Setup and installation

• Mounting bolt torque: 8 to 10 N·m
• Cable fixing bolt torque: 6 to 7 N·m
• Pulley bolt torque: 2.5 to 5 N·m
• Follow Shimano dealer manual DM-MARD001 for B tension and chain length

Specs

• Model: RD-M8120-SGS
• Speeds: 12
• Cage: long (SGS)
• Pulleys: 13T
• Series: Deore XT M8100