Swingarms

Swingarms are a fundamental part of rear suspension in motorcycles and many bicycles. They connect the rear axle to the frame and pivot about a frame-mounted bearing or pivot. The rear wheel is mounted at the far end, while the suspension system—often a shock absorber and sometimes a linkage—acts on the swingarm to absorb bumps and control wheel motion.

Configurations vary. The most common are double-sided swingarms, which bracket the wheel on both sides, and single-sided swingarms, which carry the wheel on one side. Double-sided arms offer stiffness and straightforward maintenance; single-sided arms ease wheel changes and may simplify belt or chain routing, but can involve greater complexity and weight. Materials range from steel and aluminum alloys to carbon fiber, with hollow designs to cut weight and improve aesthetics.

Operation and geometry: The swingarm pivots on the frame and moves up and down with the wheel as the suspension compresses and rebounds. Pivot location and linkage determine travel, wheel alignment, and characteristics such as anti-dive. In monoshock setups, the shock is attached to the swingarm or its linkage; twin-shock configurations use two separate dampers attached at different points.

Design considerations include stiffness, weight, bearing loads, and manufacturing processes. A well-designed swingarm maintains wheel alignment through travel to preserve steering input and drivetrain alignment. Maintenance involves inspecting pivot bearings, seals, and lubrication and ensuring proper alignment and tension of the drive chain or belt.

Beyond motorcycles, swingarms appear in some bicycle rear-suspension systems, particularly in long-travel mountain bikes and certain recumbents. Advances include lighter materials, carbon-fiber constructions, modular designs, and optimized pivot placements to improve ride feel and durability.