How To Service Boat Trailer Wheel Bearings

January, a wonderful time to service the wheel bearnings on the "new to me" rig.
On a cold winter day, Mark and Jason serviced the wheel bearings on a 2001 Lund Trailmaster 3000lb single axle trailer. The trailer has disc surge brakes and 6-bolt pattern 15-inch wheels. We photographed our experiences and attempted to layout a step-by-step process for you to follow to service your trailer. This web page is "quick and dirty," no whistles and bows, just a bunch of rough text and pictures to help another "wheel bearing service wann-a-bee" get started.

Special thanks to Mark for taking time to pose for the entire process. Special thanks to Steve for allowing us to use the shop and making the time for us to meet-up and produce the tutorial.


First get the tools to do the job.
If you ever have a roadside wheel-bearing incident, you may as well own the tools (and have them along) to do something about it. My trailer needed:
big jack
tire iron
impact wrench (probably not something you haul along, but nice to have at the shop)
large set of channel locks
small flat screwdriver
allen wrench (8mm was my size, you may not need it at all if you don't have to remove disc brake calipers)
13mm box wrench (might be a different size for your trailer, or you might not need it at all if you don't have disc brakes)
needle nose plires
old screwdriver
grease gun
grease, marine grade, do not mix with grease that contains graphite...probably not the best for a boat trailer
bearing grease tool ( can always do this by hand)
block of wood (optional, but nice)


Loosen the nuts on the wheel. Do not take them all the way off, just crack them loose.
Some trailers do not require the removal of the entire wheel (you can leave it attached to the hub), but my trailer has disc brakes and I need to access the bolts to remove the brake caliper.

Jack up the trailer.
Many people place the jack head under the leaf springs. It was OK for me, but I had to be careful to place the jack so it would not interfere with the removal of the brake caliper bolts.

Safety first:
Block your other wheel(s) and trailer "kick stand" so your trailer does not roll. If you are at home, use a jack stand as a backup.

Now use your jack to lift the trailer just enough to get the tire off the ground and remove the wheel nuts. We had an impact wrench to speed up the process.


Pull the wheel off.
If you are unfortunate enough to undergo this replacement on the road, simply toss your removed wheel under the frame as a backup. In the photo below I used a few board to raise the safety "wheel brace" just below the trailer frame.

My trailer happens to have disc brakes. If you have drum brakes (or no brakes) you can skip the next couple of steps that remove the caliper and rotor.
Below, notice the brake caliper housing around the rotor. My trailer needed a 8mm allen wrench to remove the two bolts holding the caliper. If you have disc brakes it is helpful to use a screwdriver to push the "plunger" of the brakes away from the rotor before you attempt to remove the caliper housing the brake pads. In the picture below you can see Mark using a screwdriver to push the inside brake pad toward the inside of the trailer (away from the rotor). This forces the brake fluid back into the reservoir and "loosens" the hold of the brake pads on the rotors making them easy to remove. We used a large set of channel locks on the other side of the trailer to do the same thing.

On this side of the trailer a 8mm allen wrench was required to remove the brake caliper housing. Below you can see Mark pointing with the wrench to one of the loose shoulder bolts. The other side of the trailer had 13mm bolt stud heads that were much easier to remove.

We realized that an "L" shaped allen wrench would be required to remove the lower shoulder bolt...the leaf spring was in the way.
8mm was a bit of an odd size, so my first trip to the parts store began at this time.

We carefully set the brake caliper aside onto the frame and leaf springs of the trailer. It was attached by a metal brake fluid line that was not very flexible. Not sure why a rubber hose was not used instead...cost? Next we removed the bearing buddy cover. This can be done a couple of different ways:
a) with a small screwdrive, carefully pry the cover from the hub
b) with a larger channel locks, carefully grasp the cover straight on and gently, but firmly, wiggle it up and down
The pictures below illustrate each of the possible steps.

After removing the bearing buddy cover, we used rags to remove a bunch of the grease around the hub nut. The nut is screwed on to the spindle and held in place by a lock washer. On some trailers there is a cotter pin that protrudes through a portion of the spindle and makes sure the nut does not spin off. On my trailer the lock washer had a small portion that "bent" inbetween the "studs" on the nut. I straightened the lock washer and the nut spun free.

Below is a better picture of the "spindle nut" after grease has been removed.

Here is what the nut looks like after it has been removed:

Notice the small "bendable" portions of the lock washer just below the nut. One stem of this lock washer must "bend in-between" the studs of the nut when it is tightened (also shown later during "reassembly"). The nut will not turn off if you do not bend the lock washer "out of the studs" before you attempt to turn it off. If your trailer has a cotter pin, simply straighten the pin and pull it out before you attempt to remove the nut.

Finally a flat washer (which sits right up against the outside wheel bearning) is removed. You may have to use a small screwdriver to pry the lock washer or flat washer out from the grease if it is a bit stuck. You can see the flat washer will fit only one way on the spindle...there is a flat portion on the bottom of the spindle that will guide it into place. You can also simply pull the entire hub off without removing the washer (this is what we did), see the picture below.

Now you should be able to grasp the hub, wiggle it side-to-side a bit and pull it off. Be careful, the front bearnings may fall out as you pull, so place your thumb over the hub opening as you pull it off.

Remove the front bearing. Clean off the grease with a rag. Inspect the bearing for pits, chips or undo wear. Replace it if you are suspect.  Clean the grease off of the "runway" for the bearing inside the hub. This is called the "race." Look at the "race" inside the hub. If it has scarring or is pitted or has chips, you will need to replace it. It is always a good idea to replace the race and bearing at the same time as they usually "wear together" with each other. The second wheel we did needed the races replaced. Look further down on this page to see how we did it. The picture below shows Mark pulling out the front bearing.

Here is a picture of the "race" inside the hub. Look at the shiny tapered circular runway inside of the hub that has most of the grease wiped clean.

Next we removed the seal from the back of the hub. This allows access to the rear wheel bearing. We used the blunt side of an old screwdriver as a "punch" to push on the rear bearing and pop the seal off the back. I am sure a nice metal punch would do the job as well. Make sure you set your hub on something (e.g., a couple of boards) so the rear seal is not sitting on the ground and can "pop" off the back easily. Using the punch (or blunt end of a screwdriver), push it through the front of the hub until it engages the edge of the rear wheel bearing. Once the punch is set, hit it pretty hard with a mallet. You need to pop the punch pretty good to get it started. Sometimes you can damage the seal when you do this...but don't worry, its always a good idea to replace the seals when you do this job anyway. We set our hub on top of the rotor. It fit nicely so hub was held up, but the seal was able to pop off the back and fall through the hole in the rotor. Notice the angle at which Mark is holding the screwdriver...he has it engaged with the back wheel bearing and braced in the front edge of the hub.

Once the seal is off and the bearings are out, you need to inspect them, some people clean them with parts cleaner...and if they are in good shape, pack them again with grease. It is usually advisable to use the same type of grease...and as long as you use marine grease, water resistant and specifically for trailers that will go in-and-out of water, your trailer should like you for a long time.We used a wheel-bearing packer tool. The bearing sits between two plates and grease is pumped into the bearing (five bucks at local hardware superstore). The picture below shows the grease oozing out of the bearing after it is packed in the bearing-packer tool.

Below is a picture of Mark replacing the rear wheel bearing after we repacked it with grease.

We then replaced the rear seal. We used a flat board to make sure to make equal contact all across the seal when we pounded it back into the hub. See the next two pictures. The first picture shows the seal sitting on top of the hub before it is smacked back into place. The second is the board on top of the seal.

Below is Mark gently, but firmly, tapping the seal back into the hub. You want the seal to end up flush with the back side of the hub.

We also placed a small coating of grease around the edge of the rubber seal. This may help the "seal" keep water out and grease in along the spindle.
Next we flipped the hub over and replaced the front bearing. We created a bit of a "hole" down the hub so gobs of grease would not plop out at us when we placed the hub back on the spindle.

Time to place the hub back on the trailer. Notice how Mark carefully puts his thumb over the bearing so it will not fall out. Make sure you are "straight on" to the spindle when doing usually makes it a lot easier to push the hub back on.

Next we replaced the flat washer. Notice there is only one way this washer can be placed back on due to the shape of the spindle and washer. Over the top we placed the lock washer.

After the lock washer is in place, replace the nut. Using a large plires, or channel locks (what we used), tighten the nut until it is just tight...DO NOT overtighten. Feel carefully for the "end" or when the nut is firmly down against the lock washer. When it is in place, adjust it slightly so the "bendable" portion of the lock washer can be bent up inbetween the "lugs" of the nut. You may have to slightly loosen the nut to make this happen. When the "bendable" portion of the lock washer is back in place, very gently loosen the nut until it just hits the lock washer and will not move more. You can check for "play" (a possible small amount of wiggle") in the hub by grasping the edges of the hub and attempting to "rock it" back and forth. My trailer was designed to have virtually no "wiggle" when pushing on the hub. You can check this again after you replace the tire. The tire give you more leverage to test the "play," so you may feel a tiny bit of wobble or "play." This is normal.

Below is a picture of Mark tightening the nut on the spindle.

Below is a picture of Mark pulling the "bendable" portion of the lock washer back into the "studs" on in the nut. If you have a cotter pin instead of a lock washer, you will simply have to align the studs of the nut to allow the cotter pin to be pushed through and bent.

Finally we replaced the bearing buddy cover and tapped it on with a mallet.

Be careful not to fill your bearing buddies too full of grease...they could eventually pop the back seal free and then you'll leak grease all over the inside of you wheel. We replaced the wheel, removed the jack stand and lowered the jack.... We were lucky enough to have an impact wrench. If you don't, no big deal, its just a bit more of a workout tightening the lugs.

Now, on to the other side.

As I mentioned above, the races on the second side were pitted, scarred and in pretty rough shape.
Here is a photo _attempting_ to show some of the pitting and scarring. It was a difficult shot and hard to see...I'm not sure if much of it will be visible.You can see a few "darker vertical lines" on the race. These were actually some scars in the metal. If you see these...replace your races and bearings to prevent big issues in the future.

We used a nice punch to push out the races in the second hub. We ran short on time so did not get any shots of the race-punch-out. I think there are specific tools used to replace the races, but our metal punch worked quite well. Just be careful when you re-seed the race that you do not damage the edges or punch on an edge of the actual hub.


Its a bit messy. Have lots of rags handy and be prepared to get a little dirty.
If you are going to be a boat hauler, and haul your boat on long trips, this is a valuable technique to know.

A good roadside break-down option is to simply puchase a new hub with races already installed..... I carry a spare hub with races and bearings already inside the hub in case of a roadside issue. It is much easier to simply pull the entire hub and slap on a new hub rather than mess with removing the old bearning and praying the races are still usable in the old hub. And you do not have to mess with putting in a new seal. You will have to replace the races and bearings after a breakdown anyway. A new hub for my trailer priced out at thirty compared to a tow truck and hassles.... especially if you like to fish Ontario or somewhere in the middle of nowhere.

Special thanks to Mark for taking time to pose for the entire process. Special thanks to Steve for allowing us to use the shop and making the time for us to meet-up and produce the tutorial.

Best of luck in your wheel-bearing services!

Posted on February 1, 2008