Rear Sprocket 40T 6.43 BC 520 Chain

The Rear Sprocket 40T 6.43 BC 520 Chain from M and W Aluminum Products is a precision-engineered sprocket designed for high-performance motorcycle, ATV, and powersports applications where chain drive reliability is non-negotiable. Built for riders and operators who demand consistent power transfer and extended component lifespan, this 40-tooth sprocket delivers the gear ratio optimization required for both street and off-road environments. Whether you're replacing a worn sprocket or upgrading your drivetrain, this aluminum sprocket provides the durability and performance foundation that separates reliable equipment from field failures.

Machined from lightweight aluminum alloy, the 40T sprocket features a 6.43-inch bolt circle diameter (BC) for precise fitment to 520-series chain systems—the industry standard for mid-range power applications. The 520 chain pitch (5/8-inch spacing) is engineered for optimal load distribution and engagement geometry, reducing side-loading and premature wear on both sprocket teeth and chain rollers. The aluminum construction minimizes unsprung weight, improving acceleration response and reducing drivetrain inertia—critical factors in both tactical and recreational high-performance scenarios. Precision tooth profiling ensures smooth power delivery across the entire RPM band while the measured 6.43 BC specification guarantees compatibility with OEM and aftermarket hub assemblies.

This sprocket is ideal for operators who require dependable drivetrain performance in demanding conditions—from military and law enforcement support vehicles to adventure bikes and utility ATVs used in remote or austere environments. The 40-tooth configuration provides a balanced power-to-speed ratio suitable for general-purpose riding, offering neither extreme low-end grunt nor maximum top-end velocity, making it the versatile choice for multi-mission platforms. Installation requires only basic mechanical knowledge and standard wrenching tools; verify your vehicle's hub bolt pattern matches the 6.43-inch BC and confirm 520-series chain compatibility before ordering. Pair this sprocket with a quality 520 chain and matching front sprocket for optimal drivetrain efficiency and service life.