Shimano Deore XT RD-M8100-SGS Rear Derailleur | 1x12-Speed
Shimano Deore XT RD-M8100-SGS Rear Derailleur — 1x12-Speed
This is the SGS long-cage version of Shimano's Deore XT M8100 rear derailleur, built for a compatible mechanical 1x12 mountain-bike drivetrain with a 10–51T cassette. The exact product code is IRDM8100SGS. Choosing the right cage version matters: this listing is the long-cage model for the 51-tooth largest sprocket.
What it does on the bike
A rear derailleur guides the chain between cassette sprockets and takes up chain slack as you change gears. Here, 1x12 means one front chainring and twelve rear sprockets. The long cage manages the chain-length difference across the wide cassette range.
SHADOW RD+ helps control cage movement over rough ground, while the low-profile layout keeps the derailleur tucked closer to the bike. The pulley-cage bumper helps reduce impact noise. Two 13-tooth pulleys guide the chain, with sealed bearings in the guide and tension pulleys.
Specifications
- Series: Shimano Deore XT M8100
- Model: RD-M8100-SGS; long cage
- Drivetrain: compatible mechanical 1x12-speed MTB system
- Intended cassette range: 10–51T
- Total capacity: 41T; front chainring difference: 0T
- Chain stabilizer: SHADOW RD+
- Pulleys: 13 teeth; sealed guide and tension pulley bearings
- Manufacturer average weight: 284 g
- Product code: IRDM8100SGS; UPC: 192790443645
Compatibility comes before the speed count
Match the shifter, chain and cassette to Shimano's compatible 12-speed MTB system. Twelve speeds alone does not establish compatibility with road controls, other brands or electronic shifting. Check your frame's derailleur hanger and mounting arrangement as well.
When replacing a damaged derailleur, inspect hanger alignment. Correct chain length and derailleur adjustment are still needed for clean shifts, even with a new part.
Common questions
Is this a Di2 derailleur? No. This is the mechanical, cable-operated model.
Is it for a double chainring? No. This SGS model is specified for a single front chainring.
Does the listing include a cassette or shifter? No. It is one rear derailleur; other drivetrain components are separate.
Unsure about fit? Send Go Grava your shifter model, cassette range and current derailleur model before ordering.