How to Replace Trailer Wheel Bearings

To ensure safe operation of your boat trailer, it is important to monitor the wheel bearings regularly. Noisy wheel bearings or any play in the hub can indicate that it is time to change the bearings.

Replacing wheel bearings on a trailer is not as complicated as you might think. Here we will show you step by step how to replace the wheel bearings on your boat trailer.

Removing the wheel

Step 1 – Remove the wheel

  • Loosen wheel nuts slightly to just crack the tension off them, then jack the trailer up just enough to get the wheel off the ground.
  • Remove wheel nuts and wheel.

Removing the hub assembly

Step 2 – Remove the hub assembly

  • Remove the dust cap, cotter pin, adjusting nut and spindle washer, then pull the hub towards you.

    Be careful not to let the outer bearing fall out in the process. The whole bearing assembly should come out with the hub but if it doesn’t you’ll need to remove one piece at a time.

Removing the old bearings

Step 3 – Remove old bearings

  • Remove the inner bearing and seal using a hammer and punch. Be careful not to damage the hub.
  • Clean hub assembly and remove all grease and gunk.

Inspecting the spindle

Step 4 – Inspect spindle

  • Have a close look at the spindle. Check for scoring, damaged thread or other signs of wear and tear.
  • Apply a light coating of grease on the spindle to make installation easier and assist with cooling.

Removing the bearing racers

Step 5 – Inspect hub and bearing races

  • Inspect the hub bore and cup backing shoulder for nicks and burrs and remove any if found.
  • Inspect bearing races for wear or damage, however it is a good idea to just replace them anyway when you use new bearings as most bearing kits include them.

    Bearing races can be removed by carefully tapping around the bearing race edge from behind. An old socket works really well for this job.

  • Inspect the hub for damage, then clean the hub and insert the new bearing races by tapping them in carfefully, ensuring they are fully seated in the hub.

Bearings packed with grease

Step 6 – Prepare new bearings

  • Remove the bearings from the packaging and pack with the grease. It is vitally important that you use the correct grease as it has to be specific wheel bearing grease.
  • To hand-pack bearings, start from the large side and force grease under the cage between the rollers until it shows on the smaller side.
  • Ensure the bearings are completely packed, then fill the hub with grease to the inside diameter of the outer bearing races.

Bearings installed in hub

Step 7 – Install bearings into the hub

  • Install the inner bearing and seal into the hub making sure the seal is pointed the correct way, then install the outer bearing.

Reinstalled hub

Step 8 – Reinstall the hub

  • Slide the hub onto the spindle, taking care not to damage the seal against the end of the spindle.
  • Install the spindle washer and adjusting nut.

New bearing installed and cotter pin in place

Step 9 – Adjust the bearing

  • Apply preload to the bearing before final adjustment by tightening up the adjusting nut and then backing off a couple of times.
  • Use a 12” wrench for final adjustment.
  • When the hub binds slightly, you’ll know that all parts are properly seated.
  • Back off the nut a 1/4 of a turn, then lock in place with a new cotter pin.

Adjusting the bearing

Step 10 – Install cup / Bearing Buddy

  • Place the dust cover over the hub and, using a hammer, tap around the outer edge of the cover in a cris-cross motion until it is solidly seated against the hub shoulder.
  • Use a 12” wrench for final adjustment.
  • If you are using a Bearing Buddy, follow the installation instructions on the pack.

Reinstalling the wheel

Step 11 – Reinstall wheel and test tow

  • Reinstall wheel and see if there is any play in the wheel by rocking it with your hands. If it moves too much you will have tighten the adjusting nut slightly.
  • If it all seems OK take it for a test tow.

What you’ll need:

  • New bearings
  • New cotter pin
  • New seal
  • New dust cover or bearing protector such as a Bearing Buddy

    (or a kit that contains the above 4 items)

  • Basic mechanical tools
  • Kerosene or solvent
  • Container to wash parts
  • Hammer
  • Punch
  • File or sandpaper
Water Damaged Bearings

The colour of the old grease indicates water has entered the bearings.

Bearing assembly parts

Bearing parts in order of installation:

  1. Grease seal
  2. Grease retainer
  3. Inner bearing
  4. Inner bearing cup race
  5. Outer bearing cup race
  6. Outer bearing cone
  7. Adjusting washer
  8. Adjusting nut
  9. Cotter pin
  10. Dust cap

Trailer Checks

Now that you’ve got your wheel bearings sorted, take a look at our Trailer Checks article for all you need to know about making sure your trailer is in great shape for your next fishing adventure.