Equipment > Components > Chainrings > Mountain
Description
Single-ring drivetrains succeed or fail at chain retention, and the SM-CRM81 from Shimano's XT M8000 groupset addresses this directly with Dynamic Chain Engagement technology. The tooth profile uses a slightly hooked and squared shape that grabs the chain with 150% more retention force than standard chainrings, which translates to fewer dropped chains when you're hammering through rock gardens or chattering down rooty descents. This isn't the narrow-wide alternating pattern some brands use—Shimano engineered a consistent tooth width that mates specifically with HG-X 11-speed chains for quieter operation and longer component life.
The chainring construction pairs stainless steel teeth with a carbon fiber reinforced plastic carrier body. Steel handles the wear surfaces where the chain contacts the ring, providing durability that outlasts aluminum teeth by a significant margin. The composite carrier keeps weight competitive while delivering the stiffness needed to resist flex under hard pedaling efforts. Shimano designed the SM-CRM81 as the updated version of the SM-CRM80, refining the tooth engagement for even smoother pedaling and reduced drivetrain noise compared to the original design.
Compatibility centers on the XT M8000 crankset family. The chainring uses Shimano's 96mm bolt circle diameter with a four-arm offset mounting pattern specific to the FC-M8000-1 and FC-M8000-B1 cranks. If you're running the FC-M8000-B1 Boost crank or the standard FC-M8000-1, either works with this ring. The 30T, 32T, and 34T options cover the typical range for trail and all-mountain riding—32T paired with an 11-46T cassette delivers a climbing gear that handles sustained grades without spinning out on descents.... Read More
Features
- Dynamic Chain Engagement technology provides 150% greater chain retention force
- Stainless steel teeth resist wear and extend component lifespan
- Carbon fiber reinforced plastic carrier body balances stiffness and weight
- 96mm bolt circle diameter with four-arm offset mounting
- Designed for FC-M8000-1 and FC-M8000-B1 cranksets
- Compatible with HG-X 11-speed chains
- Available in 30T, 32T, and 34T configurations
- Hollow gear construction optimizes rigidity-to-weight ratio
- Updated tooth profile from original SM-CRM80 design
- Reduced drivetrain noise during pedaling
- 11-speed single-ring drivetrain compatible
- 89 grams (30T), 90 grams (32T), 92 grams (34T)







