Tech Talk

I’m de-flated: All I hear is silence about tyre pressure


Safety is supposed to be the most important issue for any business, especially transport. We are supposed to ‘do everything reasonably practical’ to improve safety, but, are we?

Parts failure causes 4% of our truck accidents. Tyre failure accounts for 80% of that figure, especially steer blow outs. But, what are we doing about this issue?


If we knew the pressures in our tyres, that would warn the driver, giving him enough time to pull over safely, but, almost no one has Tyre Pressure Monitoring.

If our steer tyres were inflated correctly, that would be a great benefit. One hundred psi (7 bar) simply is not enough air pressure to support an axle load of 6 tonne, let alone 6.5 tonne. every steer tyre on our heavy trucks is 20% under-inflated, at the  best.

John de Pont explained this in black and white, in his PBS tyre review to the NHVR last year. Load to Inflation tables from the heavy truck tyre manufacturers recommend these pressures too.

Almost all heavy truck steer tyres are under-inflated. How can this happen in 2020? As we all know, under-inflated tyres run hot, and simply are not safe. Yet, transport continues to use 100 psi in all the truck tyres. Why are the tyre manufacturers so quiet? Why is the NHVR so quiet. Is this difficult to fix? Where is the ‘duty of care,’ and the ‘chain of responsibility?’

Most truck people like racing, F1, motorcycles, Bathurst. Most of us are motor heads. If the tyre pressures are not spot on, you lose the race. At Bathurst, a one psi mistake makes you a loser. In Formula 1, a one tenth psi mistake loses the race. Yet, we put 100 psi in all of our tyres, with no concern. Safe handling and safe working conditions are blown away.

Correct tyre pressure ‘depends upon the tyre size and the load’ (Michelin). When the load is heavy, we need high tyre pressure, and when we’re running light, we need much lower pressures.

Almost every drive and trailer tyre on Aussie roads is significantly over inflated. Check out the PBS Tyre recommendations for the correct tyre pressures on Aussie roads.

Drive tyres are at least 30% over inflated, while trailer tyres are 70% over inflated ’at maximum legal load.’ When lightly loaded, they are usually 300% over inflated!

Does this make sense? Does over-inflation affect safety? Sure does.

Way back in 2012, Australian Road Transport Suppliers Association (ARTSA) proved that a lightly loaded semi would stop at least 15% shorter, with the right pressures! That is two semi lengths at 80k’s. Stopping quickly is a vital safety issue. Yet nothing has happened since!

Two years ago, AIR CTI financed ARRB to test tyre slip angles on their specialized test semi rig. The results proved that slip angles increase at least 15% when tyres are over inflated. Slip angle affects trailer tracking, emergency maneuverers, and jack knifes. This is another vital safety issue.

We as an industry must do ‘everything reasonably practical’ to improve safety, or we can go to jail.

Yet, we are still driving ‘blind,’ with no idea of our tyre pressure, especially on the critical steer tyres.

Why are our steer tyres 20% under-inflated? We know under-inflation is dangerous. Our government regulators know our steer tyres are under-inflated. The tyre manufacturers know our steer tyres are under-inflated. Our tyre fitters should know and understand this too. Yet, all I see is silence.

Why are the engineers and regulators so quiet? Are they not governed by ‘Chain of Responsibility’ laws?

Our environment and greenhouse gases are supposed to be hugely important to our future, yet, no one cares about tyres. We could save at least 400,000 tyres per year, if we ran the right tyre pressures. Fuel use would decrease too. Yet, silence again.

Drivers are the backbone of our industry. High vibration levels, from rough roads, amplified by over-inflated tyres are killing our drivers, our trucks, and our roads. Isn’t this important too?

We have electronic aids galore on our trucks. EBS, ABS, ESC, all work by applying braking which is transmitted through the rubber to the road. That bit of rubber contact is vitally important.

So our drivers drive blind, on under-inflated steers, and over-inflated drive and trailer tyres, risk- ing lives, damaging our drivers, our trucks, our roads, and our environment. Our industry is wasting billions of dollars, on something so easily fixed.

I am astounded by the silence. If I fail to adequately inform my employees, I can go to jail. If I operate a vehicle that is unsafe, I can go to jail.

Our regulators know the importance of matching tyre pressure to the load. Tyre manufacturers know this too. Every racer knows that tyre pressures are vital if he wants to win. Tyre pres- sures are absolutely vital for every truck operator, if safety is important, if truck life is important, and if profits are important.

My question is: How can our regulators and tyre suppliers sleep at night? How can they get by with their silence? Where is their ‘Chain of Responsibility?’

Ring me or email me for any reason. This is my passion and life. Chet Cline, 03 51276128

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