CAT 9U-9559 Self Aligning Bearing

CAT 9U-9559 (9U9559) is a Caterpillar self-aligning spherical plain bearing (spherical plain bearing) suitable for steering/boom articulations in off-highway trucks/excavators. It is compatible with high-quality YM/SEM/GD replacement parts. The following are the core technologies and compatibility information:

Core Technical Parameters
Item Details
Part Model CAT 9U-9559 (9U9559) Self-aligning spherical plain bearing (spherical plain bearing, suitable for steering/boom articulations, withstands high radial + bidirectional axial loads, allows ±5° misalignment, compatible with YM/SEM/GD replacement parts)

Core Materials Outer ring: Bearing steel (GCr15, HRC 58–62), Inner ring: Bronze alloy (CuPb10Sn10, cadmium-plated for rust prevention), Spherical surface: PTFE composite layer (0.2 mm), with lubrication grooves + 3 M8 lubrication holes, compatible with lithium-based grease (NLGI) 2. -30℃ to +120℃

Key Dimensions: Inner diameter 114.3 mm (4.5 in), outer diameter 187.3 mm (7.374 in), width 119.1 mm (4.689 in), spherical radius 57.15 mm, mounting surface runout tolerance ≤0.03 mm, compatible with M24×2 bolts (mounting hole spacing 170 mm)

Single Weight: Approx. 8.5 kg (18.74 lb)

Compatible Models: CAT 785B/785C/785D/785G off-highway trucks (steering articulated), 390D/390F excavators (boom/stick articulated), commonly used with 9U-9558 outer ring and 126-1859 pins

Working Fit: Rated radial load 520 kN, rated axial load 260 kN, coefficient of friction ≤0.08 (lubricated condition), operating temperature -40℃ to +150℃, suitable for heavy-duty articulated impact conditions.

Core Functions and Structural Features:

Automatic Alignment Compensation: Spherical sliding design allows for ±5° shaft misalignment, compensating for frame/boom deformation, reducing articulated stress, and adapting to dynamic positioning under complex working conditions.

Heavy-Duty Wear Resistance: CuPb10Sn10 bronze inner ring + PTFE composite layer, impact load resistance 600 kN, wear rate ≤0.01 mm/1000 hours, suitable for heavy-duty impact conditions on construction sites.

Long-Lasting Lubrication: With circumferential lubrication grooves + 3 radial lubrication holes, grease is evenly distributed on the spherical surface, reducing dry friction and extending maintenance intervals to 2000 working hours.

Compatible Replacement Parts: YM/SEM/GD quality parts are consistent with the original equipment manufacturer (OEM) in material, dimensions, and tolerances, offering near-OEM compatibility and durability, and higher cost-effectiveness.

Modular Assembly: Modularly assembled with the 9U-9558 outer ring and 126-1859 pin, simplifying replacement procedures and adapting to CAT articulated standard interfaces.

Installation and Maintenance Points

Installation Specifications: Clean the mounting surface, ensuring it is free of rust, oil, and burrs. Bearing housing tolerance: +0.02–+0.04 mm, ensuring precise fit.

Cold press installation (pressure head pressure ≤100 kN). Do not strike the spherical surface to avoid damage to the PTFE layer.

Tighten symmetrically with M24×2 bolts (grade 10.9), torque 320–350 N・m, controlling the preload clearance to 0.05–0.10 mm.

Maintenance Recommendations: Add lithium-based grease (NLGI 2) every 1000–2000 working hours, 50–80 g each time, until old grease is removed.

Inspect for spherical scratches, PTFE layer peeling, and outer ring cracks; replace immediately if any abnormalities are found.

Prioritize replacement parts from CAT original manufacturers or YM/SEM/GD quality parts of the same specification, ensuring compatibility with the outer ring and pin.