For proper truck wheel bearings maintenance, there is a checklist of maintenance items that should be checked before driving.
In most cases, the standard list includes oil level and tire pressure, while trailer wheel maintenance is often forgotten. Checking the bearings in the wheel assembly to determine if they need to be replaced or serviced is critical to safe trailer operation.
Below are step-by-step instructions for maintaining these important pieces of trailer equipment as part of your annual maintenance.
1) (Dis)mounting required
When disassembling a tire from a trailer, you must be especially careful: If you damage the hub or spindle while removing components, a simple maintenance job can turn into an expensive repair involving complete assembly.
Remove the tire and wheel assembly, hub cap, cotter pin, adjusting nut, and washer. Then carefully pull the hub assembly toward you to loosen the outer bearing cone. Once this is loose, remove it and pull the hub assembly off the spindle. This should include the inner bearing cone assembly, inner shell, outer shell, and seal. Use a seal puller to remove the seal and expose the inner bearing cone assembly. Discard the seal and remove the inner bearing cone assembly from the hub.
Assess the bearing assemblies. If they are damaged or corroded, it is time to replace them. To do this, use a cup pusher or mild steel rod to remove the inner and outer cups from the hub assembly. If they are not damaged and you are just cleaning the assemblies, you can skip this step.
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Once the assembly is disassembled, assess the condition of the bearing.
2) Assess the bearing
Using kerosene or mineral spirits, remove all the old lubricant from the hub cover, hub assembly, spindle, bearings and bearing shells, and other components. Once the surface is clean, you can assess whether the hub and spindle have any major damage.
If the damage is minor, i.e., debris, nicks, or burrs, remove them with a fine file, wire brush, emery cloth, or honing stone. If the damage is not repairable, you will need to replace the hub and spindle.
Next, inspect the bearings and bearing shells for wear, discoloration, pitting corrosion, or other damage. Replace the bearings and bearing shells if necessary.
3) Proper lubrication
Apply a thin film of grease to the spindle, race, seal, and the inside of the hub and hubcap. The grease will prevent dry running and protect the metal parts from corrosion and premature bearing damage.
Then fill the tapered roller bearings with an approved grease. If you are using conventional grease (NLGI No. 1 and 2), you should press a ring of grease into the entire circumference of the wheel hub until it is half full. If the hub is more than half-filled, churning and higher temperatures may occur, which can damage the bearings. Then coat the inner wall of the hubcap.
4) Reassemble the hub
Drive the inner and outer hub shells into the hub assembly with a hub driver or mild steel rod until they are firmly seated against the hub shoulders. Be careful not to damage the surfaces of the bearing shells – and never use a bearing cone to drive the shell in.
At this point in the assembly, you should install the inner bearing cone assembly and replace the grease seal. Follow the manufacturer’s instructions for the alignment of the seal lips. Use the proper installation tool to avoid damaging the seal. Then slide the hub assembly back over the spindle, being careful not to damage the seal on the spindle. Finally, install the outer bearing cone, washer, and adjusting nut onto the spindle.
5) Adjustment of the bearing
After the hub assembly is reassembled, it is important that the bearings are properly adjusted. The incorrect adjustment will shorten the life of bearings, seals, and other wheel-end components.
First, tighten the adjusting nut to 25 ft-lbs while turning the hub. This should cause the bearing to clamp slightly, indicating that the parts are seated properly. Back off the adjusting nut one-sixth to one-fourth of a turn to allow 0.001 to 0.005-inch end play. Place the locking clip over the adjusting nut and insert the cotter pin to prevent the adjusting nut from turning back.
Using a dial indicator, place the base as close to the center of the hub as possible. Once it is near the center of the spindle, set the dial indicator to zero. Hold the rotor at 3 o’clock and 9 o’clock and push it axially as you move the wheel back and forth. Stop and read the pointer. Then perform the same procedure while pulling the rotor toward you.
The bearing clearance corresponds to the total movement of the indicator, which should be 0.001-0.005 inches. If it is not, turn the axle nut in the appropriate direction and recheck the bearing clearance.
When you have completed all checks, reinstall the hubcap and tire and wheel assembly, remembering to tighten the lug nuts according to the manufacturer’s recommendations.
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