SRAM's GX Eagle 12-speed rear derailleur is the mechanical, cable-actuated long-cage workhorse of the Eagle lineup — the one that shows up on more trail and enduro bikes than probably any other 1x12 derailleur on the market. It borrows the same shifting architecture as XX1 and X01 Eagle but swaps the forged aluminum cage and titanium clutch spring for a traditional aluminum cage and steel spring, which is where the price break comes from. If you're rebuilding a drivetrain, replacing a rock-strike casualty, or building up a frame from scratch, this is the derailleur that lets you run the full Eagle system without paying flagship money.

The Type-3 Roller Bearing Clutch eliminates derailleur bounce and chain slap when you're rallying over punishing trails, and the X-Horizon design limits horizontal derailleur movement that contributes to ghost shifting, while X-Actuation keeps shifting sharp and consistent across a 1x drivetrain. The 14-tooth X-Sync lower pulley is what makes the wide-range cassettes possible — a larger pulley wraps more chain and manages the geometry needed to jump onto that 50 or 52-tooth climbing cog cleanly.

Compatibility is the piece to pay attention to. The GX Eagle derailleur is designed to work with SRAM's 10-52T cassettes and is backwards compatible with the 10-50T cassettes , so you can spec it against whichever Eagle cassette you're running without a second thought. It requires an Eagle-compatible 12-speed shifter and Eagle chain — the cable pull ratio is Eagle-specific and will not work with 11-speed SRAM shifters. Mounting is standard direct-mount to your frame's derailleur hanger; there's no UDH or hangerless interface here, which is what separates this mechanical GX from the newer T-Type Transmission derailleurs.... Read More