DIY Bearing Service
  |  First Published: September 2005

Trailer maintenance – two words that none of us really want to say or even hear. What is trailer maintenance and where do you start? There are plenty of ideas and opinions floating around about just what is important and what is not; what should be done and how often.

I believe that your trailer bearings are the most important trailer parts for general maintenance. Bearings should be serviced every 3 to 6 months and replaced every 12 months.

A lot of people now use Bearing Buddies and are under the false assumption that because they are using Bearing Buddies they do not need to carry out the normal service schedules. Bearing buddies, if used correctly (which rarely happens) will certainly help maintain your bearings but should never be used as a replacement measure for a good bearings service.

servicing your bearings

In this article I will be going through the steps involved in completing a bearings service. The principle applies to basically any type of bearing that you are servicing. You may find though that some of the components are slightly different or as you get into heavier duty axles, they may get much bigger.

Taking apart the hub

Firstly you want to get the trailer set up on level ground, the wheels chocked and the hand brake applied so that the trailer can’t move once you take the wheel off to access the hub. Once you have the trailer in position, take a wheel brace and loosen the wheel nuts. Then place your jack under the fish plate (the plate that the u-bolts go through to hold the axle in place) and jack the trailer up until the wheels are just clear of the ground and can be removed.

After the wheels come off the real bearing service begins. Take a hammer and gently tap the dust cap in a few places until it comes off, you should now see some grease and when you wipe that away you should see a castle nut and a split pin. Remove the split pin from the castle nut and then remove the nut. The hub should then be ready to be pulled from the axle. The hub will sometimes be hard to get off; this will depend on how often you service your trailer bearings.

If you have not serviced your trailer for a while, you might even have to give them a tap with the hammer to get it off the axle stub. There are times when we have had to bash the hubs off and use an Oxy to heat the inner bearing up to get it off the axle. The more frequent the service schedule is, the less likely you are to have trouble. Once the hub is off you can inspect the axle stub to make sure there is no visible damage.

Next, drop the washer that sits behind the castle nut out and the outer bearing out and place them on a clean rag. You will then need to knock the rear seal out and take the inner bearings out as well.

Cleaning the hub and bearings

Once you have the bearings out, clean the hub and the bearings to remove the old grease. You can use several different products for this, including petrol. When the bearings and hub are clean, inspect them for wear. In the hub you will find a metal insert (cup and cone) that the bearing sits against; you will need to check both the inner and outer to make sure that the surface is not pitted or damaged. Run your finger over the surface and feel for any imperfections in the surface. Then inspect the bearings to make sure there is no damage to the cage of the bearings and make sure all the needles look fine. If you are happy with the inspection, you can start to pack and put the hub back together.

Repacking the hub

When you pack the bearings, make sure the grease is forced through the bearing and in behind the needle rollers. You will also need to take some large fingers of grease and place them into the hub. Try to fill the hub with grease so that when you place it on the axle you will have virtually no air pockets inside.

Now you are ready to start to re-assemble the hub. Turn the hub over so that you can put the rear bearing in first. Place the inner bearing back into the hub and take your hammer and knock into place the rear seal. We recommend a single piece seal, but there are also two-piece seals available (it’s a matter of heated discussion as to which is the better way to go).

Turn the hub over and place the last of your extra grease in through the front of the hub. Place the outer bearing into the front of the hub followed by the washer.

Next, place the hub back onto the axle. The hub may or may not slide all the way onto the axle stub. Once you have got it as far as you can, place the castle nut back onto the end of the axle and do the nut all the way up until it is tight.

The hub should now be pushed all the way onto the stub and be locked in place so that it can’t spin at all. Gradually back the castle nut off until the hub starts to move freely. This does not mean that if you give the hub a flick that it will spin by itself but that you do not feel undue friction. While doing this, be aware of lining up the hole in the axle with the slots in the castle nut so that the split pin can be put back in. When you feel the hub is spinning freely, give it a slight pull to make sure that there is no movement. If it moves when you pull it then it is too loose.

Place the split pin back in and bed it over so that it can’t pop out. Place the dust cap back on and you are finished.

Replacing your bearings

The difference between a service and a replacement of the bearings is quite simple. Follow all the procedures as for a service but once you have the hubs off, throw the bearings away. Then, knock out the cup and cone (these are the metal parts that are in the front and back of the hub that you would have inspected when you did your service). You will feel that there is a slight lip at the back of each one.

Place the hub on a solid surface and using a punch, work evenly all the way around the lip until the cup is knocked out. Turn the hub over and repeat for the other side.

Then clean the hub for any last grease and knock the new cups and cones back into the hubs. To do this, make sure that the hub is again on a solid surface and sit the cup or cone (depending on which side you do first) over the hub (make sure you have it facing the right way). Take a hammer and gently work your way around the cup or cone, tapping it into the hub. Once the cup or cone is tapped flush with the top of the hub, use your punch to drive it the rest of the way home. Make sure that it is knocked all the way to the seat in the hub.

When the new cups and cones are in place, simply follow the same procedures as for a service to finish the job. Repeat this process for all the hubs. I recommend that you use good quality bearings and replace the rear seals every time you carry out a bearing service.

Once you have completed your bearing service or replacement for the first time you should be able to carry out future bearing services in 20 to 30 minutes per hub.

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