Boat Trailer Wheel Bearing Maintenance & Repair Tips

Boat trailer wheel bearing maintenance includes repacking your trailer’s wheel bearings, which should be done once a year at the very least to keep your boat's trailer running smoothly.

Repacking trailer wheel bearings should be done even more often if the trailer is frequently exposed to salt water. Here are some trailer wheel bearing maintenance tips, including tips for repacking them. 

Inspect Dust Seals and Bearing Protectors

Remove the axle dust covers and check the color of the grease. If the grease has a milky color, it’s a sign that water has entered the hub and mixed with the grease. Water intrusion is usually caused by an ill-fitting axle dust cap or a faulty bearing seal. Replace the seal and change the dust caps if there are signs of water intrusion, and make sure to get new bearing protectors if they’re damaged or worn.

Inspect Bearings and Bearing Races

Check the old grease that the seals, washers, and bearings were packed in for small metal filings or fragments, which are an indication that the bearings and/or the races have worn. A blackened color for the grease indicates the hub has been overheating. Overheating hubs are generally caused by failed wheel bearings or by the axle nuts being over-tightened. Replace worn bearings and bearing races immediately.

PRO TIP: Use a bearing race tool to seat the new races within the hub. If you don’t own a bearing race tool set, take one of the old races, position it over the new race and carefully hammer the old race to set the new race into the hub.

Inspect the Axle Stub and Axle Nuts

Check the old bearings and the axle stub for signs of discoloration. If the metal is slightly yellow, it’s a sign the bearings are overheating. This can be caused by a worn bearing or by the axle nuts being too tight. Replace the bearings without over-tightening the axle nuts when reinstalling them.

NOTE: Never over-tighten axle nuts. The nut should be tightened to the point that the wheel can still spin freely without resistance, but not so loose that there is any lateral movement in the wheel.

Repack Trailer Wheel Bearings with Grease

Repack the wheel bearings and hubs with a saltwater-resistant grease, even if you mainly use your trailer in fresh water.

NOTE: Don’t over-grease the bearing protectors when refitting them or you’ll blow out the bearing seals. Check whether the protectors need more grease or not by pressing the pistons. If the piston doesn’t move, it needs more grease.

Replace Bearing Races

Install new bearing races into old hubs by pre-loading them to ensure they’re fully seated within the hub. Otherwise, they might get loose and cause bearing failure. Tighten the axle nut to the point the wheel encounters resistance when it’s spun, then tighten the nut another half-turn. Next, rotate the wheel a dozen times to ensure the races are fully seated and loosen the axle nut to its correct torque. 

Test the Wheel Hubs

After repacking the bearings, reassembling the hubs and replacing the wheels on the trailer, tow it for a few miles, then put your hand on each hub to feel for excessive heat. If a hub feels too hot, there’s a problem. An overheating hub after an overhaul is usually caused by incorrectly seated races or an over-tightened axle nut. 

Correct the axle nut first, and if that doesn’t fix the problem, disassemble the hub again and double-check that the races are properly seated.