Trailer safety is vital!

Trailer safety is vital!

FOCUS delved into the problem of poor trailer maintenance in the second issue of the year. This time around, VIC OLIVER offers some practical advice for fleet operators to use in the workshop

Drawbar and semi-trailer maintenance is poor in many fleets. Often the only time that the trailer gets a good inspection and service is when it is being prepared for the yearly Certificate of Fitness test – or when the trailer breaks down along the road.

To ensure that trailers remain in a healthy, roadworthy and safe condition they need to be inspected and serviced regularly.

A poorly maintained semi-trailer can damage the truck tractor – or, in the case of a drawbar, the rigid truck – that is pulling the trailer. This applies particularly when coupling an old trailer to a new vehicle.        

If the trailer brakes are not working correctly, the truck will have to do all the braking, which will result in excessive brake wear. Similarly, if the trailer’s wheel alignment is not set correctly, the truck will have to work harder to move the rig in a straight line and it will use more fuel.

Well-maintained trailers eliminate expensive roadside breakdowns and enhance vehicle productivity. There are a number of critical items and components on trailers that need to be checked and serviced regularly. These include:

Rubbing plate and kingpin

On semi-trailers the rubbing plate needs to be checked to ensure that it is not bent or scored, as a damaged rubbing plate will quickly damage the fifth wheel. This could result in it having to be replaced long before it would normally be necessary.

Check the kingpin for wear and regularly clean and grease the rubbing plate and kingpin.

Towing drawbar

On drawbar trailers the drawbar, tow-hitch eye and pin must be inspected regularly. Also clean, grease and check the trailer turntable.


The following components of the brake system need to be checked:

• Brake lining or pad thickness;

• Brake lining to drum clearance, the linings
must also be in contact with the drum when the brakes are applied. Adjust slack adjustors if necessary;                                            

• The cables of the ABS system (if fitted) must be connected and the system must be working;

• Brake slack adjusters and camshafts operations;

• All Suzie hoses and all brake piping connections;

• The load-sensing valve and connections;

• Any air leaks in the system.                                  

Furthermore, the emergency trailer brakes must be checked by disconnecting the red emergency Suzie hose: the emergency brake should be activated immediately.

Trailer safety is vital!Drain the air-tank reservoirs of any water (this should be done daily by the driver). Clean and grease all brake operating parts and test the brakes on a brake roller tester (if available).

Wheels and suspension

Check all tyres for damage and excessive and abnormal wear. Tyres must be inflated to the correct pressure and valve caps must be fitted. Examine all wheel rims and fastening nuts; all wheel nuts must be correctly torqued.                                                                

Check suspension and shock absorbers. Replace worn or broken parts.

Wheel bearings

Check all wheel bearings for play and adjust where necessary. Service and maintain according to the axle manufacturer’s recommendations.

Wheel alignment

Regularly check and adjust wheel alignment. A quick tip, regarding tandem and tri-axle units, is to measure the distance from the front rim to the rear rim on one side of the trailer. Now compare the same distance measurement on the other side of the trailer. If the distance is not the same, the wheel alignment of the trailer will need to be professionally measured and adjusted.


All electrical wiring must be in good condition and all lights and indicator lamps must be working. Remember to also check the electrical Suzie connection.

Under-run bumper and chevron

The rear under-run bumper and chevron must be fitted and must comply with the legal specifications.

Reflective tape

Reflective tape must be fitted and should be clean of dirt and grime.

One of this country’s most respected commercial vehicle industry authorities, VIC OLIVER has been in this industry for over 50 years. Before joining the FOCUS team, he spent 15 years with Nissan Diesel (now UD Trucks), 11 years with Busaf and seven years with International.

Published by

Focus on Transport

FOCUS on Transport and Logistics is the oldest and most respected transport and logistics publication in southern Africa.
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