Fitting cheap replacement parts can have lethal consequences

By Colin Windell

Truck and trailer braking safety entails a combination of the driver’s expertise in handling their vehicle, and the materials specified for the brakes. Using the cheapest brake parts just to save costs could become very costly, and have lethal consequences indeed.

South Africa's heavy vehicle transportation sector is a highly competitive industry, and those involved in it are constantly looking for ways in which to reduce running costs.

Most transport companies understand that investing in a top-quality truck and trailer will ultimately deliver the lowest cost per kilometre. However, once this vehicle is out of warranty, and the time comes to start replacing (for example) brake linings with aftermarket components, opting to purchase the least expensive products may not be the most financially prudent decision.

"A highly critical part of any truck and trailer combination is the braking system. All too often, we read of truck and bus accidents, which are invariably very serious,” says Transportation Components’ Sales Manager Patrick Bruinette.

Bruinette explains that the sheer weight of a truck and its load tends to amplify the consequences of an accident, as does the number of passengers carried in a bus.

"For this reason, when it comes to heavy vehicle brakes, the quality of both the maintenance and the aftermarket parts that are fitted as replacements are of crucial concern,” he says.

Truck and bus accidents are often blamed on faulty brakes. However this is not always the case, Bruinette observes, as the way in which drivers operate their vehicles and use their brakes is also a significant cause of accidents.

“For example, in the case of a truck-and-trailer combination, we find the drivers drive down hills using the trailer control valve only, which means only 50% of the braking system is being applied. The problem arises when an incorrectly-used braking system starts overheating, which reduces the available brake friction, causing brake-fade and diminishing stopping efficiency.

Friction material has certain restrictions - the hotter the friction material gets, the less stopping power it has. This loss is called ‘friction fade’.”

On the other hand, ‘brake fade’ happens when the brake drum heats and expands; and the brake chambers have to push out further to exert effective force on the drum. The longer the stroke of the diaphragm-type brake chamber, the less efficient braking becomes, and is consequently referred to as ‘brake fade’.

Apart from poor driving habits, maintenance - or the lack thereof - is another contributory factor in many truck- and bus accidents today. For example, Bruinette has experience of supplying parts for a truck that had been driven from Harare to Johannesburg with the brakes on only two of its eight wheels actually in working order.

"Unfortunately, incidents like this are all too common," he says.

Most mechanics who work on heavy vehicles understand the safety-critical nature of their work, but they have little or no control over the quality of the aftermarket components they are instructed to fit.

In the very competitive heavy transportation industry, those in procurement are frequently under pressure to keep costs to a minimum. In addition, fleet owners/operators often do not fully understand the very considerable differences in price-related quality which exist in components such as brake linings.

Transportation Components has taken samples of its brake lining friction material and tested them in a laboratory, which has given them a rule-of-thumb guideline as to the durability of various friction materials in service.

“Compared to various lining materials from second-tier manufacturers, our friction material, made to original equipment manufacturers (OEM) specification, namely Duroline brake liners and Eren disc pads, proved to between 30% and 50% more durable,” says Bruinette.

"We put a lot of ongoing effort into educating fleet owners and others in the transportation industry about the varying quality of brake friction material."

Bruinette however cautions that, for companies importing components, the South African Bureau of Standards (SABS) issues a ‘letter of authority’ (‘LOA’), which gives permission to import specific components provided these parts meet certain minimum standards.

Fleet owners need to be aware of this, and when buying low-priced components need to ask to see the supplier’s LOA, in order to ascertain whether it is legally correct; and whether the components which are being procured meet the required standards.

Heavy vehicle owners/operators also need to be aware of potential issues in the relining of brake shoes. This is a highly specialised operation, particularly when it comes to riveting linings to brake shoes. A special piece of equipment is required to make sure the rivets are both removed and fitted correctly.

“There have been instances where rivets have been simply drilled out, a procedure that tends to enlarge the hole in the shoe. Sometimes brake relining shops will use one size of rivet - irrespective of the size of the mating hole in the brake shoe. Substandard practices such as these can lead to problems when shoes that have been relined in this way are refitted to trucks,” Bruinette advises.

A further important aspect that those involved in the maintenance ‘chain’ – from the fleet or vehicle owner to the mechanic – need to be aware of, is the importance of adherence to the specifications on the data plate (which is usually attached on the side or at the back of the vehicle).

However, experience has shown that the specifications on the data plate are quite often ignored, says Bruinette. Trailers in particular are often given only cursory maintenance, even if the truck-tractor receives very thorough levels of maintenance.

“It is vital that trailer brakes are maintained according to the specifications on the data plate, as it is the trailer that has to actually carry the load. The trailer brake system contributes at least 50% of the complete vehicle combination braking system,” he continues.

“Too often the focus is on the initial purchase price of the vehicle - with subsequent disregard of the quality of components required to keep the ‘rubber on the road’ and the vehicle operating at peak efficiency, reliability and safety.”