Bearing 6201tu/2a

This aftermarket deep-groove ball bearing is engineered for the SYM Jet X 125I 125cc scooter, compatible with 2021-2022 model years and cross-referenced to OEM number 90912-M9Q-000-M1. Bearings are among the most critical components in any rotating assembly, and their failure can cascade into expensive secondary damage if not addressed promptly.

The 6201-series bearing specified for this application supports the front wheel hub assembly, maintaining precise rotational alignment between the stationary axle and the rotating wheel rim. With an inner diameter of 12mm, outer diameter of 32mm, and width of 10mm, this compact component must handle radial loads up to 6.8 kN from vehicle weight and cornering forces, plus axial loads up to 3.1 kN from braking and steering inputs. Despite these significant loads, the bearing must operate with minimal friction and noise across a temperature range from -30°C winter starts to 120°C sustained high-speed operation.

The bearing construction begins with rings and balls manufactured from chrome steel (AISI 52100), a material chosen for its excellent fatigue resistance, dimensional stability, and cost-effectiveness. The steel is vacuum-degassed to reduce non-metallic inclusions that can initiate fatigue cracks, then through-hardened to 60-64 HRC to provide wear resistance on the raceways and rolling elements. The 2RS (two rubber seals) configuration features synthetic rubber seals on both sides of the bearing, providing IP65-level protection against dust and water ingress. The seal design incorporates a steel-reinforced lip that maintains contact pressure against the inner ring land through a garter spring, creating a dynamic seal that excludes contaminants while retaining lubricant.

The internal lubricant is a lithium-based grease (NLGI Grade 2) formulated with corrosion inhibitors, anti-wear additives (ZDDP), and a base oil viscosity of 100 cSt at 40°C. This grease provides adequate lubrication film thickness at startup while maintaining fluidity at operating temperature. The calculated L10 life exceeds 50,000 km at average urban speeds of 40 km/h, meaning 90% of bearings will survive this distance under normal loading. For reference, L10 life is the industry standard metric based on Weibull statistical distribution of fatigue failures.

Technical parameters: bore 12mm; outer diameter 32mm; width 10mm; dynamic load rating C=6.89 kN; static load rating C0=3.10 kN; limiting speed 22,000 RPM (grease lubrication); seal type: contact rubber on both sides (2RS); cage: stamped steel, ribbon type; radial clearance: C3 (loose fit for press-fit outer ring); material: AISI 52100 chrome steel; lubricant: lithium complex grease, 30% fill.

Replacement is indicated when: wheel rotation exhibits roughness, notchiness, or excessive free play exceeding 0.2mm radially; the seal shows damage or grease leakage; or after 30,000 km of service in wet or dusty environments. Always replace wheel bearings in pairs to maintain symmetrical loading and prevent uneven tire wear. During installation, press the bearing squarely into the hub bore using a driver tool that contacts the outer ring only—never apply installation force through the balls or inner ring, as this can cause brinelling (permanent indentation of the raceways). Pack the hub cavity with additional grease to extend service life, and verify that the bearing rotates smoothly before final assembly.