Wheel bearings: they’re the components that keep your wheels turning, literally, and for that reason it’s vitally important to make sure they’re always in tip-top condition. Depending on towing conditions, that may mean changing them more frequently than you think you need to. Following some simple steps, it’s a relatively simple DIY job. This is how you do it.
Many people put this job off because either they’re intimidated by it or they think that they can do ‘just one more journey’ before it’s necessary. Then a wheel comes off on your towing trip, with potentially disastrous consequences – consequences that would’ve been completely avoidable if a few simple maintenance steps had been followed.
The frequency with which you change your towable’s wheel bearings is dictated by the distance travelled and how arduous the journeys are; I allow 30 000 km for highway use and 15 000 km for off-road. If the towable in question is a boat trailer and you occasionally get your axle submerged, especially in the sea, then it’s advisable to remove, clean and inspect the bearings much more frequently, as salt and bearings definitely do not mix!
Tools and materials for the job
The task is well within the capabilities of any competent handyman; you will need the following to carry out the job:
·Two axle stands
·Large flat screwdriver
·Ring spanner: somewhere between
·17 and 24 mm (a shifter isn’t ideal)
·Large pin punch (6-8 mm diameter, with nice sharp edges)
·Your new bearings
·Two pieces of hardwood, say 50 x 50 x 100 mm each
·Two new 2.5 mm x 40 mm split pins
(Job duration: approximately two hours per wheel)
Step 1: Wheel and hub removal
Park the vehicle on a level, firm surface and place the wheel chocks firmly on either side of the wheel opposite the one you’re going to work on.
Place one of the axle stands under the drawbar coupling and retract the jockey wheel. This prevents the vehicle from swivelling about the chocked wheel, falling off the axle stand and injuring you.
Loosen the wheel nuts on the side you are working on, but do not remove them yet. Jack the axle until the wheel clears the floor by about 20 mm. Insert the second axle stand firmly under the axle. NEVER trust a jack when you (or even just parts of you) are under a vehicle.
Remove the wheel nuts and the wheel.
There will be a domed grease cover over the centre of the wheel hub. This can usually be removed by tapping a flat screwdriver into the groove behind the ridge on the dome and the edge of the hub. Work your way around the dome as you do so. Gentle radial taps using a small hammer may assist in getting it loose.
With the dome off, the retainer nut will be accessible. This will either be a castellated nut (a nut with the cut-outs all around the top) or have a hexagonal sleeve over it which reduces to a castellated centrepiece. There will be a split pin through one of the castles and through the hole in the stub axle, with the ends bent over the tip of the axle. Remove it.
Now, if you are working on the hub on the right side of the vehicle, the axle and nut will have a normal right-hand thread. But if you are on the left side of the vehicle, the thread may be left-handed. Remove the nut and the washer behind it. Sometimes the axle has a shallow keyway and the washer will have a tab which fits the keyway. (This stops the washer from spinning with the bearings.)
Once you have the nut and washer off, you should be able to remove the cone of the outer bearing. If it doesn’t oblige, just rock the edges of the hub until it eases out of the cup. (The cone is the caged assembly of rollers and the cup is the ring they run in.)
Once you have the cone off, the hub should slide off the stub axle quite easily. (If you have a braked trailer this is the time to check the brake shoe wear and the condition of the drum’s inner braking surface.)
You will find an oil seal at the back of the hub, covering the inner bearing. Don’t bother to dig it out, it will come away with the cup (the outer bearing race) when you remove it.
Step 2: Removing the inner and outer cups
The inner and outer cups are very tightly pressed into the hub. Each presents a very slight inner shoulder accessible only from the opposite end of the hub.
Place the hub on the hardwood blocks. Start by reaching in to the shoulder of the inner cup with your punch while tapping it with the hammer. Work your way around the cone and it will gradually drift out of its seat in the hub, carrying the oil seal with it. Remember which way the taper of the cone faces!
Turn the hub over, and now, working from the inner side, remove the outer cone in the same manner.
Step 3: Cleaning and cleanliness
From here on, the secret to long bearing life is cleanliness. Thoroughly clean the hub cavity and the stub axle.
Clean all grit and dirt from your hands and tools and clean your workbench surface.
Step 4: Reassembly
Unwrap the new bearings and place the cones to one side.
Coax the new cup into the recess by laying it onto the lip and tapping on it with the piece of hardwood laid across it. Be careful not to get the cone jammed into the hole at an angle. Once the
outer edge is flush with the hole, continue to tap it in right to the inner shoulder, using your pin punch progressively all around the edge until it gives a nice solid ring as you tap it.
Repeat with the other cup.
Pack the inner cone with grease. Be sure to squeeze the grease right through it, then place it into the inner cup, with the taper the right way.
The oil seal can now be fitted in the same way, except you will not have to use your pin punch, just the hardwood block. Be careful, as it will easily get damaged.
Fill the cavity in the stub axle to about 50% with grease.
Fit the hub back onto the CLEAN stub axle and fit the greased outer cone, tabbed washer and castellated nut. Tighten the nut until you just can’t turn the hub, then back it off until the hub rotates freely, but without any wobble. If you cannot see the split-pin hole, back off a little more so that you can fit a new split pin and bend it over.
It’s not really necessary to put any grease into the cover dome, but I usually give it a smear anyway. Tap the dome back into place, replace the wheel and nip the wheel nuts.
Check the wheel rotation for any excess ‘wobble’ once more. Adjust again if necessary. Finally, lower the vehicle and, very importantly, remember to tighten all the wheel nuts firmly.