Advice: tyre pressures – know before you blow!

The single main cause for truck tyre issues is incorrect pressure, but maintaining your truck's tyre pressures isn't as simple as it may initially seem…

I was riding my motorbike along the Hume Freeway near Sydney and flicked out of the slow lane to overtake a B-Double.

Irregular rotation on a tyre in the middle tri caught my eye and I backed off quickly. A few seconds later there was a loud bang and a shockwave that I felt in my stomach and chest.

A cloud of dust and debris partly shrouded the rear trailer as I dodged the bits of tread and carcass that bounced down the road. Had I been beside the tyre when it blew, I'm sure I'd have visited the shrubbery…

It started me thinking that most of us take tyres for granted, but an inflated tyre stores an enormous amount of energy – particularly truck tyres, which have several times the air volume of car tyres and are inflated to at least twice the pressure.

Every inflated tyre is a potential 'bomb'.

Most tyre fitters are familiar with the photo of the European tractor tyre fitter whose remains were smeared across the roof of a tyre shop. He was inflating a large tyre, without putting it in a safety cage, when the phone rang, so he left it connected to the compressor while he went into the office.

Several minutes later he remembered the tyre and walked back into the workshop, just in time to be caught by the blast and mashed into the ceiling.

Even when the inflating and fitting procedure seem to be done correctly, there can still be great danger.

The Queensland Coroner recently handed down a report on a fatal incident involving a truck driver on a mine site. He was killed when a tyre he had just fitted to a trailer blew out as he lowered the jack and the tyre contacted the ground. His chest was crushed instantly by the pressure blast when the sidewall 'unzipped'.

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The tyre in question was marked: 'SLOW LEAK/OK' and that, the Coroner found, was the clue to this tragic accident.

At some stage in its life this tyre had suffered a puncture that resulted in a slow leak, but was subsequently repaired. Expert witnesses concluded that the tyre must have been operated outside its optimal pressure range before repair and had developed serious internal damage, despite the fact that there was no visible sign to speak of.

The Coroner recommended that: "The [mining] industry investigate, and implement within two years, remote, or wireless, tyre pressure sensing equipment to allow operators to monitor tyre pressures from within the cabin of the truck."

No truck would ever be put into service without driver alerts for low oil pressure and high coolant temperature, yet the critical safety situation with tyre pressures has been left to, at best, a pre-trip gauge check, or, more commonly, a tap with a tyre lever.

I've found, over years of driving all sizes of vehicles all around Australia, that any car or truck tyre that has run loaded and underinflated for more than a few minutes should be condemned, because it's impossible to know how much carcass damage has been done.

The key to preventing that underinflated operation is TPMS (Tyre Pressure Monitoring System) and all my vehicles have it fitted.

My experience with quality TPMS systems is that they alert the driver immediately there's a pressure drop, allowing the vehicle to be stopped as soon as possible.

Tyre pressure monitoring is often confused with on-board tyre inflation that varies tyre pressures through driver control, depending on road and load conditions.

TPMS doesn't increase or decrease pressure, it simply indicates real-time pressures in each tyre and gives audible and visible alarms to the driver.

TPMS is not just a safety issue: it saves fleets money. There are plenty of reports on TPMS implementation overseas and in Australian fleets that show reductions of up to 50 per cent in overall tyre and downtime costs.

Electronic tyre pressure monitoring is now mandatory in many countries, but not yet for heavy vehicles. The reason is that most TPMS technologies are inadequate for the heavier tyre loads, temperatures and higher pressures of heavy truck and trailer tyres. Also, some truck fleets use liquid tyre sealant, and that's not compatible with many in-wheel sensors.

There are heavy-vehicle, valve-cap-replacement systems available and I've had good test results with the Doran TPMS that I've been evaluating for the past six years.

This design uses a large valve-cap transmitter and battery and is sealed, so that it's mine-safe. My battery-life testing indicates around five years before replacement of the cap is necessary.

Interestingly, Volvo Trucks' factory-fitted TPMS is also a valve-cap type.

In-wheel TPMS has the advantage of being out of damage risk during normal operation, but requires recalibration if the wheel is moved to another location on the vehicle or to another vehicle. A valve-cap type is simply unscrewed and put onto a fresh wheel.

Another possible direction for the TPMS issue is on the horizon, literally, because 'smart' tyres have been released overseas and are headed our way.

A smart tyre has a radio frequency identification (RFID) chip integrated in its construction, but it's a chip with much more capability than previous RFID tags that have served mainly as product identifiers.

The new tags include sensors that measure temperature and pressure and can relay that information in real time. Smart tyres generally send real-time information to a database, often cloud-based, so fleets can track tyre information for short-term and long-term operational and efficiency improvements.

In the short term, a driver can receive alerts if a tyre needs more air or requires replacement.

All major truck tyre manufacturers have developed such sensors and software platforms to measure and monitor tyre performance.

Continental's ContiPressureCheck uses a rubber-mounted sensor that measures pressure and temperature and is attached to the inside of any brand of tyre. It integrates with the truck's telematics system to provide readouts to the driver. ContiConnect relays that info to the driver's base and also to entry and exit gate readers at any fleet depots he visits.

Goodyear's Tire Optix uses a hand-held or armband-mounted readout that remotely measures tyre pressure and tread depth.

Pirelli has a pressure readout that works through a smartphone app.

Bridgestone is working on integrated RFID chips that can remain functional and in place during its Bandag retreading pressure and heat processes.

Before these smart systems become readily available and widespread, the need for some form of TPMS on every truck is paramount, I reckon. Why be in doubt about critical tyre pressures when a positive readout is possible?