camper trailers tech tips

servicing wheel bearings

 

 

 

 

Servicing Wheel Bearings

    Servicing your own wheel bearings as part of your trip preparation or part of regular maintenance is one job you should feel confident in doing if you own a camper trailer. This way you know the job has been done properly and what state the bearings are in.

     How to breaking down your trailers hub is knowledge that could be very handy on the side of the track, not only for you, but perhaps in helping someone else that is in trouble miles from anywhere.

 

 what to look for

    Bearings comprise of two parts, the cup which is pressed into the hub and the cone which is the part that contains the rollers of the bearing. The bearing on the inside of the hub flange, the side closest to the centre of the trailer is called the inner bearing, while the bearing on the outside is called the outer bearing.

    When inspecting the cone look for signs of wear, pits, chips or discolouration to the rollers which is usually a purple or blue colour. The cup should also be inspected for wear, damage or scoring marks. If any damage is found they should be replaced.  

Bearings should always be replaced in a set with cup and cone together.

    Then we cannot forget the bearing seal which is located at the rear of the hub and stops water and dust entering the bearings. The seal is an important part of the bearing assembly and one which should not be overlooked when inspecting your bearings. Look for any damage like an oversize inside diameter or cuts and abrasions.

    Wheel bearings come in different sizes depending on their use and are matched to the load rating of the trailer. Three things that affect the strength of an axle include the diameter of the steel, the design load of the bearings and the design load of the stub machining.

    When travelling into the remoter regions of our great outdoors it is always a good idea to carry a full set of bearings and seals in your spares kit. It is also worth knowing they are going to fit by trying the cones in place, but not necessarily pressing the cups in. A better idea is to replace your present bearings, hub, cone & seal with a new set and keep these as spares. You then know they will definitely fit in an emergency on the roadside. Nothing worse than getting out your spare bearing set and find they donít fit.

 

getting them apart

     The cone can be removed and the new one re-seated in an emergency situation with a screwdriver, however a copper dolly is the best tool for the job. This will not damage the machined surface of the cone in case you slip. If you have a machinist mate you could get him to turn down a short length of pipe to drive the cone home.

     All bearings and seals have a serial number stamped on them. Some camper trailers may have mismatched components like Holden bearings and a Falcon seal depending on the load rating of the axle and hub assembly. Make sure you have the right parts in your spares box.

     While you have everything apart it is worthwhile checking the stub for cracks. The area in question is where a 'step' has been machined on the stub to receive the wheel bearings. This is the most likely place for a fracture to occur, however it is also important that you check all machined steps on the stub.

    The fracture usually starts on the bottom so it is often not seen until it is too late. Pay particular attention to all underneath areas of machined 'steps'. Best way to feel if a crack is present in a machined surface is by running your finger nail over the area or with the aid of a small mirror.

    Make sure the camper is properly supported with suitable stands and do not place any part of your body under the camper.

    It is a good idea to place the wheel you have taken off under the axle.

 

learning to do it

   
So how do you go about doing a wheel bearing inspection and replace the bearings and seals on your camper? There is nothing better than hands on experience when learning a job like this. It is not hard, anyone can do it. If you have a mate that knows how to break down a hub, why not ask him to come around one afternoon and then throw on a barbie after.

    You can also ask your local mechanic to do the job and ask if you can watch so you are able to make repairs on the side of the track. Donít forget to ask how to remove and replace the cones on the hub.

    If you are a member of a 4wd, camper trailer or caravan club you could ask the host of the weekend get together if they could organise a workshop on this subject.

    At the last three Australian CamperTrailers Group national meets I have conducted a practical workshop on breaking down one of my own camper trailer hubs, showing how to inspect the bearings, remove the cone and inspect the axle. Then putting it all back together again including the technique of pushing grease into the bearing.

    You can also find suitable material on the net.

    A large shifter or spanner is needed to remove the centre nut on the stub. It is always handy to have a few extra split pins too.

    Most importantly always think safety first and never get under the trailer when it is supported on stands alone. Park the trailer on firm level ground and block the trailer tires on the opposite side securely so that no forward or rearward movement is possible. Jack up the trailer following the manufacturers instructions and secure the trailer on jack stands of adequate capacity front and rear. Then release the handbrake and undo the wheel nuts and remove the wheel.

     When finished donít forget to tighten your wheel nuts like I did once. The wheel came off rolling into the bush chewing all the wheel studs in the process. I now carry a spare set of wheel studs and nutsÖÖ. funny now.

     Again there are a number of different wheel studs & nuts used on camper trailers depending on the axle, hub and bearing combination used. For example Landcruiser hubs are popular for off road camper trailers. To replace a stud, simply hammer out and a new one hammered back in on the track side, lining up the grooves. 

     You may find it a little difficult lifting the wheel back on if you have a crook back or bad knees. A 10Rx15 tyre and steel rim combination weighs around 30 kgs. Squatting down and lifting this weight at arms length can be difficult. Be careful you don't bust your poofle valve.

     I have found it much easier to lift a wheel into position using a 'lifting helper'. Most use a wheel brace to do this, but anything close to hand like a stick, tent pole, axe, shovel etc will do the job.

     After placing the 'lifting helper' on the ground under the centre of the hub roll the wheel into position, slightly under so the top of the wheel leans out. Rotate the hub to align the studs with the holes in the rim, then holding one hand on top of the wheel, raise the end of the 'lifting helper' (which will be positioned next to your leg) and push the top of the wheel forward towards the hub. The wheel should slip straight into position onto the wheel studs with little or no effort.

     Just a note on bearing dust caps with a grease nipple or Bearing Buddies which are designed to prevent water entering on boat trailers. Adding too much grease can cause the rear seal to be pushed out allowing water & dust to enter and cause premature failure, usually at the inopportune time. It is best to look inside the hub, inspect the bearings and regrease, rather than to just pump grease in.

 

safe jacking

1  park the trailer on firm level ground.
2  block the trailer tires on the opposite side securely so that no forward or rearward movement is possible.
3  jack up the trailer following the manufacturers instructions.
4  secure the trailer on jack stands of adequate capacity front and rear.
5  release the handbrake.
undo the wheel nuts & remove the wheel.

 

getting your hands dirty

1  pry off the dust cap using a flat bladed screwdriver.
2  straighten out the cotter pin that holds the bearing nut & remove it.
3  remove the bearing nut and washer.
4  pull the brake drum forward along with the front bearing.
remove back bearing
6  remove rear seal.

             

           

    Don't mix up the bearings if you are doing more that one wheel at a time - each bearing must mate with it's original race. The bearings wear in & need to be matched with their respective counterparts.

 

bearing & race inspection

1  thoroughly clean the bearings and other parts in kerosene until all the old grease is removed & set aside to dry.
clean the hub and spindle.
3  inspect the bearing races for heat discoloration, pitting, scoring & any unevenness.
4  inspect the bearing for damage as above. Any out of round rollers, cracked roller cages and rough running will indicate replacement is required.
5  the bearing & both inner & outer races must be replaced as a set.

 

axle inspection

    This gives you a good opportunity to check the condition of the axle while you have everything apart. Pay particular attention to the area where the 'step' has been machined to receive the wheel bearings as this is the most likely place for a fracture to occur. The fracture usually starts on the bottom so it is not seen until it is too late.

    Another area worth checking is at the start of the machining itself. This area may be covered by the 'weld ring' if you have brakes on your trailer. You will have to remove the backing plate to get a better look at the suspect area, usually four or six bolts, but it will be well worth the effect. 

    Best way to feel a crack in a machined surface is by running your finger nail over the area. Not be afraid to get your magnifying glass out to be sure. An axle failure at highway speeds in not much fun.

 

     

     

                               

 re-packing the bearings

1  place a small gob of wheel bearing grease in one palm.
2  grasp the bearing with the other hand so that the wider end is facing the grease.
3  force the grease into the gap between the inner race & the outer cage so that it squeezes up through the rollers.
4  press the bearing down into the grease in a rocking motion & continue until the grease oozes up.
rotate the bearing 1/4 turn at a time & continue until the bearing is completely filled with grease.


 

reassembly

1   put some grease into the interior of the hub with your fingers & spread it around the circumference of the hub.
2  place the inner packed bearing into its place in the hub.
place a new seal on the hub and tap it into place with a hammer until it seats fully.
4  be sure to wipe off any grease that finds it's way onto the outer flat surface of the seal.
5  replace the drum onto the axle spindle, insert the outer bearing, thrust washer and axle nut.

 

           

 

preloading the bearings

1  tighten the axle nut by hand until it is tight. Tighten another 1/4 turn with spanner.
2  spin the drum several times to distribute the grease evenly in the bearings.
3  back off the nut with the spanner until loose & retighten finger tight.
4  insert a new cotter pin to lock the nut in place & bend it over the spindle.
re-install the dust cap, wheel & tire.

 

replacing the bearings

The bearing must be replaced with a complete new bearing with the inner and outer races.

1  the inner races are pressed into place in the hub & must be driven out.
2  use a brass punch to catch the edge of the race by passing it through the inverted hub. A few good whacks with a hammer should drive out the old race.
3  place the new race into position and tap it in with the hammer and punch. Take care not to mar the surface of the race.

 

getting the wheel back on

    You may find it a little difficult lifting the wheel back on if you have a crook back or bad knees. A 10Rx15 tyre & steel rim combination weighs around 30 kgs & squatting down & lifting this weight at arms length can be difficult. Be careful you don't bust your poofle valve.

    I have found it much easier to lift a wheel into position using a 'lifting helper'. Most use a wheel brace to do this, but anything close to hand like a stick, tent pole, axe, shovel etc will do the job. Here's what you do.

1  after placing the 'lifting helper' on the ground under the center of the hub,
2  roll the wheel into position, slightly under so the top of the wheel leans out.
3  rotate the hub to align the studs with the holes in the rim.
holding one hand on top of the wheel, raise the end of the 'lifting helper' (which will be positioned next to your leg) & push the top of the wheel forward towards the hub.
5  the wheel should slip straight into position onto the wheel studs with little or no effort.

 

                   


info by Rob

 

 

July 2005  
updated may 2009