Installing a trailer turntable bearing correctly is a critical process that ensures the safety and longevity of your trailer. It's a complex task that requires attention to detail and following the manufacturer's specific instructions. However, there are some general best practices that apply to most installations.
Inspect the mounting surface: Before you begin, the mounting surface on both the A-frame and the trailer chassis must be completely flat, rigid, and free of any debris, burrs, or paint thicker than 50 mm. Any unevenness (max. 1 mm) can be corrected with shims or plastic metal.
Check the bearing: Ensure the new bearing is the correct type and size for your trailer and that it's in good condition. The bearing may have a "soft zone" marked with an "S." This soft zone should be positioned in a non-load or non-constant load area during installation.
Gather your tools: You'll need high-tensile bolts (grade 8.8 or higher), a torque wrench, and potentially a special tool for pressing in cups or seals, depending on the bearing type.
Never weld the bearing: The turntable bearing itself should never be welded to the trailer frame or A-frame. Welding can damage the bearing and compromise its integrity.
Positioning: The lower ring of the turntable is typically bolted to the A-frame, and the upper ring is bolted to the trailer chassis.
Bolting: Use a minimum of 8 high-tensile bolts per flange. For smaller bearings, 4 to 6 bolts may be sufficient. The mounting bolts should be tightened in a crosswise pattern to ensure even pressure.
Torque: Tighten the bolts to the manufacturer's specified torque. The pre-tensioning force on the bolts should be approximately 70% of the bolt material's yield limit. Using a leveling washer is recommended, and spring washers should be avoided.
Shear load: To relieve shear load on the mounting bolts, it's recommended to weld at least four blocks immediately next to each flange.
Pre-lubrication: Many new turntable bearings are supplied with a base coating of lubricant, but they must be thoroughly re-lubricated before the trailer is put into operation for the first time.
Grease type: Use a high-quality ball bearing grease, typically a lithium-saponified grease of NLGI class 2.
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