Australian Trailers commonly use a taped roller bearing for trailers from 750kg up to 4.5t. Popular trailers stop at 4.5t due to legal braking requirements mandating expensive air brakes.
A bearing set consists of a grease seal, inner bearing, outer bearing and dust cap.
The Grease seal prevents grease escaping through the inner bearing when the bearing cavity is overfilled. Air expansds when the hub get hot forces and grease though the rear seal when overfilled. It is important not to overfill the bearing cavity by leaving 50% capacity for air expansion.
The inner or rear bearing is the main load carrying bearing under normal load conditions.
The outer bearing is the main load carry bearing under extreme circumstances for example, cornering.
SHOCK LOADS
Bearings often incur what we call shock loading. Shock loading is the term we use when loads exceeding normal recommended loads are placed on components including bearings.
To cater for shock loading we recommend selecting a loading of 25% extra capacity when designing your trailer or when upgrading your trailer.
DUST CAP
The dust cap is the most underrated and forgotten part of the bearing kit.
The dust cap is a compression fit and should be replaced after removal. Dust caps are made from mild steel and shaped to compress the outer ring to grip the hub boss when inserted.
Once compressed, the dust cap loses a little compression every time it is removed.
Your dust cap is the first sign you bearings are failing. When travelling, occasional put your hand on your dust cap and feel for heat.
If you feel heat increasing in your dust cap then your bearings are wearing rapidly and must be replaced next stop. Dust caps should run COLD.
A sign of bearing wear when you remove the dust cap is BLACK grease. The black colour in the grease is carbon black released from the surfaces of the bearings.
Once the outer hardened surface of the roller bearings have been worn, the bearing will produce heat and fail quickly.
If not replaced your hub will overheat and expand causing your dust cap to lose compression and fall out.
Once the dust cap falls out, you only have a few mile to makes it home before disaster strikes and the wheel falls off.
There you have it, feel the dust cap for heat and you stay in good shape during your RV holiday.
Trailer Bearings
Trailer Parts
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