The Shimano SM-RT81 Disc Rotor Lock Ring is a small but critical component that secures your center-lock disc brake rotor to your wheel hub. Whether you’re installing a new rotor or servicing your braking system, this lock ring ensures the rotor stays firmly mounted during high-load braking and demanding riding conditions. Designed for use with Shimano’s Center Lock interface, the SM-RT81 provides reliable, tool-compatible fastening so your rotor remains true and secure ride after ride.

Manufactured to Shimano’s exact standards, this lock ring threads onto the hub’s splined center-lock interface and clamps the rotor in place, preventing axial movement and ensuring consistent braking performance. Its robust steel construction resists wear, impacts, and corrosion from road grit and environmental exposure. Easy to install and remove with the appropriate lock-ring tool, the SM-RT81 is essential for anyone running Center Lock rotors, whether on mountain bikes, gravel rigs, or road bikes equipped with disc brakes.