Avoiding front tyre blowouts

A blowout of a front tyre on a heavy-duty truck or bus can be extremely dangerous, as the driver loses all steering and directional control – especially if the vehicle is loaded. This, writes VIC OLIVER, often results in a very serious and sometimes fatal road accident involving other vehicles.

Although I have never had the misfortune of experiencing a front tyre blowout on a vehicle whilst I have been driving, I have interviewed truck drivers who have been involved in accidents resulting from this.

One interview remains strongly imprinted on my mind. I conducted it with a very experienced truck driver who lost control of his heavy-duty soft-drink delivery truck following a blowout. As a driver who loved his job and his truck, he was very upset about the damage to his vehicle.

This driver told me that he had been unable to steer the truck, in spite of the power-steering assistance. With no steering control, he was powerless to stop the vehicle from veering off the road; it eventually came to a stop when it hit a rock in a small riverbed. Luckily, no other vehicle was involved and nobody was injured in the accident.

As the tyre that had burst was reasonably new, in good condition, and correctly inflated before the start of the trip, the driver and his manager were puzzled as to what had caused this failure. On further investigation, it was found that the front axle was overloaded due to incorrect loading of the payload.      

On the day of the accident, the forklift driver – whose job it was to load the palletised cargo onto the vehicle at the depot yard – was absent. An inexperienced forklift driver was therefore called in to load the vehicle. His lack of understanding regarding the importance of mass distribution on the vehicle was compounded by his failure to consider the relative weights of the pallets loaded with product contained in small cans versus the pallets bearing liquid in two-litre bottles.

The stand-in forklift driver therefore loaded the vehicle incorrectly, placing all the heavier pallets containing the bottles in the front of the truck body and the lighter pallets containing the cans at the rear, resulting in the front axle and tyre overload that caused the blowout.

Incorrect mass distribution resulting in front-axle overload is just one of many potential factors that may cause tyres to burst. Incorrect tyre pressure is another common cause of front-axle tyre failure. The walls of an underinflated tyre, for example, are subject to more pressure and stress, which means it will quickly overheat and fail – especially when the vehicle is heavily loaded and/or travelling at speed on a hot day.

Furthermore, it is important to avoid the poor practice of bleeding tyres after they have been running and warmed up, resulting in a higher tyre pressure than when the trip began.

Many truck and bus operators, meanwhile, disregard the importance of missing tyre valve caps. Without the tyre valve cap fitted, dirt can enter the tyre valve causing the tyre to gradually lose pressure and fail.         

Tyre condition is obviously also an important factor. Tyres should be inspected regularly to ensure that the tread depth is sufficient and that no visible tyre damage has occurred.

As with most potential problems that can lead to accidents, a proactive approach to tyre management, maintenance, and load distribution can go a long way towards minimising the risks of a tyre blowout.