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12 Steps To Repack Or Replace Your Trailer Tire Bearings

Your boat trailer wheel bearings need regular care. Here's how the pros do it.

Bearing assembly exploded illustration

Image: Charles Wegman, CE Smith Co.

Statistics from the GEICO | BoatUS Marine Insurance files show that almost one out of every four calls from members with a trailer broken down along the side of the road is about bearings gone bad. Some boat trailers use a more modern oil-bath hub design for bearings, but most use grease, which is why we're spending some time with Chris Grimm of Legendary Trailer Repairs in Maryland to find out how to perform this maintenance item yourself. If you aren't confident in your abilities, consult a qualified pro.

Technical Support

Difficulty: Moderate

Tools and Materials:
  • Jack and stand
  • Large flat screwdriver
  • Needle-nose pliers
  • Lug wrench
  • Channel locks or seal puller
  • Hammer
  • Soft hammer (made with brass and designed not to damage surfaces upon impact)
  • Round punch or wooden dowel
  • Piece of scrap board
  • Goggles
  • Gloves
  • Boat trailer bearing kit with the proper size bearings, races, and a double lip grease seal. Note: Bearing kits are usually one of five sizes: 3/4", 1", 1-3/8", 1-1/4", 11/16". If unsure, each bearing and race has a stamped part number
  • Bearing grease (don't mix brands)

Time: One hour for each wheel

Cost: Approximately $30–$40 for a complete set of bearings and seals

1. (Not shown) Jack the trailer tire on one side high enough so that the tire spins freely, and place a jack stand beneath the frame. Chock the opposite trailer wheel. Some folks prefer to leave the trailer connected to the tow vehicle. Shake the tire up and down and from side to side. If there is movement, chances are good the bearings are bad. Spin the tire and listen for sounds. In many cases, bad bearings can be heard, but be aware this can also be nothing more than brake pads or shoes catching the hub. Often there is a discernible difference in the sounds.

Removing dust cap

2. Remove the dust cover or Bearing Buddy with a screwdriver. If the grease is milky, water has entered the bearing assembly. If the grease has a different color, it can mean newer grease was added. Wipe all grease away with a rag or towel.

Removing cotter pin

3. Remove the cotter pin, castle washer (some trailers have castle-style axle nuts — see diagram above — in which case there's no castle washer), axle nut, spindle/axle washer and set aside for safekeeping as you'll be using them again. Shake the tire, and the outer bearing should come off. Wipe away bearing grease (look for evidence of metal, which points to a bearing or race failure) and inspect for signs of wear including discoloration (a gold color is evidence of heat) and scoring, pitting, or dents. If you see any of these, it's time to replace rather than repack the bearings.


Avoid cleaning bearings and races with gasoline. This can harm the inner seal. Paper towels and rags do the job.

Pull the wheel off the spindle and lay it with the inner sidewall facing up. Inspect the axle spindle for visible damage and then feel it with your hand. The surface should be smooth.

Removing grease seal

4. Remove the grease seal. Notice the grease on the inner hub in this photo. That's proof the inner seal has failed. Use channel lock pliers or a seal puller to remove the seal. Remove the inner bearing and inspect it just as you did with the outer bearing in Step 3. NOTE: Anytime you remove the inner seal, replace it.

Removing grease from the inner bearing

5. Just like the outer bearing, the inner bearing is seated in a race, also called a bearing cup or a bearing cone. If the bearings are in good condition, remove all the remaining grease in the hub and inspect both inner and outer races for pitting, scars, and/or discoloration. If everything looks good, all you need to do is repack with fresh grease and a new seal and cotter pin. (Go to Step 7.) However, if any show signs of wear, replace everything. If a bearing shows wear but the race looks fine, still replace both.

Getting the races out of the hub

6. Getting races out of the hub requires placing a round punch against the inside edge of the race and with small taps with a hammer, moving in a circular motion to dislodge it from the hub. The inner race is removed with the outer sidewall facing you and the outer race is removed with the inner sidewall facing you. If you don't have a round punch, a wooden dowel can work. Whatever you choose, wear eye protection. Place a new race on the hub and with a soft hammer, tap the race all the way in with a circular motion so that its outer edge is flush with the hub. Alternatively, you can position the old race above the new one and tap it in that way. There's even a race insertion tool available at auto parts stores if you prefer. You'll know it's in the proper position because it won't go in any farther and the sound will change when properly seated.

Greasing the inner hub

7. Grease the inner hub, then pack the inner bearing with grease. Legendary Trailers uses a bearing packer (pictured), which can be found at most auto parts stores for less than $30. Another method is to put grease in the palm of your hand and then place two fingers of your other hand through the larger side of the bearing. Now pack grease into the bearing rollers while rotating the bearing into your palm. You'll do the same with the outer bearing later.

Double-lipped gease seal

8. Now install the new and double-lipped grease seal. Double-lipped grease seals have a better chance of keeping water out of the bearing assembly than single-lip seals. It's usually included in bearing kits so be sure to ask or do some research prior to buying. Many prefer using a board across the seal to hammer against, thus protecting the seal. You have now completed the inner bearing assembly!

Installing outer race

9. Turn the wheel over and install the outer race. Then lift the wheel onto the spindle being careful not to poke the grease seal with the spindle's outer edge. Grease the race and add the outer bearing.

Installing spindle washer and axle nut

10. Next, add the spindle washer and axle nut/castle nut, tightening until it stops. The nut should be a snug fit, but if too tight, the assembly can be damaged as a result of heat generated when the trailer tires are going down the road. If too loose, the wheel will wobble. Finally, add the castle nut or the castle-style axle washer.

Installing new cotter pin

11. Now put a new cotter pin on the assembly turning both ends in the same direction to lock it in place.

Buddy Bearing

12. Add the Bearing Buddy or dust cap and spin the wheel. You shouldn't hear any sound except your own voice saying, "Yes!"

4 Signs Of Bearing Wear

1. The hub feels hot to the touch during refueling stops on the highway. This can also be the result of a brake shoe or brake pad rubbing while traveling.

2. There is grease on the bottom of the boat hull near the trailer wheel or grease on the trailer frame near the trailer wheel.

3. You can hear obvious noise when spinning the wheel while it is jacked up.

4. If the usually reliable dust cover comes off suddenly, this can be the result of excessive heat and pressure buildup in the bearing assembly.


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Pat Piper

Contributor, BoatUS Magazine

Pat Piper has written for many magazines including BoatUS Magazine, Chesapeake Bay Magazine, and Diabetes Health and has written/ghostwritten eight books. He's currently an executive editor for Westwood One Radio.