Tyre Safety. What does it mean?

Adam Gosling - Wednesday, December 02, 2015

Tyre safety standards in Australia are being further called into question following the number of fatalities and serious injuries in the mining industry.

Not only the coroners but also the unions are pointing to a deficiency.

Australia has developed one of the few standards (AS 4457) for dealing with mining tyres anywhere in the world but injuries and deaths are still occurring.

Tyres are composite flexible pressure vessels. Unlike household gas cylinders which are rigid steel pressure vessels (like most compressed air receivers) a tyre has a load placed on it, is rolled over unkind surfaces and is generally ignored until it goes flat.

Tyres are specifically excluded from the pressure vessel standard (AS1210) with OTR tyres (>24” rim diameter) being covered under AS 4457 and any on road tyres falling under Section 25 of the Australian Design Rules (ADR).

When you stop to consider things in detail a tyre is the only connection between your vehicle and the road.

The average passenger car requires tyres to perform steering braking and some minor suspension functions as well as supporting the load (passengers and baggage). A giant mining truck tyre is required to support up to 100 tonnes, relying on the air it contains within to support that load. If there is insufficient air to support the load the tyre doesn’t complain or refuse to work like an engine or gearbox.

It just gets on with the job and literally tears itself apart performing the function we ask it to do, right up to the point where it can no longer function and fails, sometimes catastrophically. Tyres for passenger vehicles have large safety margins engineered into them during the design phase.

This is to provide a margin of safety for abuse or lack of attention but it is of course wiser to keep tyre pressure constantly monitored and the best way of doing this is to use an automatic pressure monitoring system (TPMS).

In the US, the TREAD Act mandated tyre pressure monitoring for all light passenger vehicles manufactured in that country from 2008 on.

The EU followed suite in 2012, Korea in 2013. The importance of tyre inflation pressures was mentioned by President Obama last year.

He indicated that safety on road networks is directly affected by poor tyre pressure maintenance, more fuel in consumed than is necessary thanks to tyres not being maintained correctly as well as resources being wasted.

To most people tyres are a grudge purchase. They shouldn’t be.

Tyres are what keeps us safe, keeps our vehicle on the road performs the steering and braking functions as well as ensuring comfort. It is not unusual to find that until a tyre goes flat there is little if any attention paid to it, yet the car has been washed and polished, the air freshener changed and windows cleaned.

For tyres that work hard (mining and transport) correct pressure maintenance is even more important. It is no longer adequate to check tyres when the vehicle has its periodic maintenance. Both the mining and the transport industries have for many years been monitoring engine oil pressures using gauges and electronic aids from inside the truck cab, even transmitting this data to the maintenance office so problems can be identified prior to failure.

Tyres on the other hand are still stuck in the 1950’s using a hand held gauge to check pressures, well, every so often.

So how do we tell what the tyre pressure is when we’re driving down the road? We don’t until it goes flat.

In 2015 electronic tyre pressure monitoring is not only feasible but is mandated on passenger cars. Passenger car tyres have an easy life, rarely carrying their full loads, over‐engineered and able to sustain a lot of neglect and abuse.

Compare air in a tyre to oil in an engine. If the quantity of oil in an engine is not correct then the engine will wear out faster, overheat and even destroy itself. If a tyre does not have sufficient air it too will overheat and wear out quickly.

It will also consume a lot more fuel as it overheats and then fails, sometimes unfortunately with disastrous consequences.

A tyre is not just a single piece of rubber but a composite of many different rubbers all performing a specific function.

There are steel wires within a tyre that perform other functions and all need to be operated within the manufacturers range of recommended inflation pressures. Like all mobile equipment if it is operated outside of the manufacturer’s recommended range then failure is probable if not imminent.

Whilst tyres appear simple they are a highly complex engineering feat. Adhering rubber to steel is a science all on its own, having certain types of rubber (such as tread rubbers) remaining hard enough to wear yet flexible enough to roll is another required attribute.

There are no hard and fast rules to identify issues or problems with tyres, the easiest suggestion is “if it doesn’t look right it’s probably not”.

Above all a tyre requires the correct inflation pressure. Every tyre has this same requirement.