Tech Talk

Truck tyres: Are we being conned?

Chet-Cline---issue-24

Our tyre experts and our government regulators are not telling us vital information, information necessary to save lives, reduce damage to driver’s health, that is costing transport tens of thousands of dollars per truck, and costing our country billions of dollars, while needlessly damaging our world.

Why? Because they sell lots more tyres! Making billions of dollars more every year!

Australia has over a million heavy truck tyres rolling on our roads, at a rough value of $400,000,000!   

We could reduce tyre use by 30% by using the correct tyre pressure.  A further 10% are ruined by uneven tyre wear and blowouts, easily saved by using a Tyre Pressure Maintenance System, or Central Tyre Inflation. A 40% savings exceeds $160,000,000 dollars every year.

It gets worse: One third of all single truck fatalities are caused by steer tyre failure! 

We lost 171 heavy truck drivers in the last 12 months.  Work related fatalities is 13 times higher than other workers.  An average of 74,530 working weeks is lost every year.  Muscular stress and mental stress top the list.   Driver stress and high vibration levels are a major cause.

Whole Body Vibration is a known killer, yet our government ignores our roads and our tyre pressures.

Most tyre manufacturers do little to inform transport, tyre fitters, and regulators about optimising tyre pressures.

Yes, Load to Inflation tables are available on the internet, showing tyre pressures matched to the tyre load and size. But, is this information available at your tyre dealer?   Does the tyre manufacturer explain matching tyre pressures to the load? Has your dealer explained this, or does he just tell you to run 100 psi or 110 psi in all of your tyres?

Tyre and rim associations also publish Load to Inflation tables, but, again, where are they?   

The first tyre manufacturer also printed charts, both for Australian roads and USA roads, showing tyre tread life reducing at any pressure above the Load to Inflation recommendations. In fact, they showed a 22% tread life loss at only 20% over inflation.   Who’s telling the truth? I’ll put my money on the company that invented the radial tyre.

Yet, even they won’t recommend any tyre pressures under 70 psi (heavy truck tyres)!  Why not, you should ask….

The reasoning is, USA regulators class a truck tyre that is under half the ‘molded in’ maximum tyre pressure as a flat tyre!

And most heavy truck tyre maximum pressures are 130 to 140 psi! 

In fact, almost all truck tyre manufactures won’t recommend any pressure under 70 psi. Why?

Let’s look at the evidence

The USA Tire and Rim Association ‘Bible’ has Load to Inflation tables that go down to 25 psi, when equipped with Central Tyre Inflation, and working at speeds under 80 kph.   At 25 psi, the load can be up to 2,300 pounds (just over a tonne per tyre).

Internal engineering papers, from one tyre manufacturer, recommends highway pressures for 110 kph highway speeds of 2 bar (29 psi) with a load of 1 tonne per tyre.   Yet, no one is telling us, or the regulators.

Two years ago, the USA Technical Maintenance Council’s ‘Future Truck’ division stated that tyre pressures must match the load, for safety and profitability.

Last year, the National Heavy Vehicle Regulator commissioned a PBS tyre review. It recommended the following pressures for Aussie semi trailer rigs, fitted with 11R 22.5 tyres, at maximum legal weight: 120 psi steer, 75 psi tandem drive, 55 psi tri axle trailers.  Has this information reached transport or tyre fitters? Nope.

So, almost all of our heavy trucks are running steer tyres 20% under inflated, tandem drive tyres 33% over inflated, and trailer tyres a whopping 85% over inflated, when fully loaded.  Empty, drive and trailer tyres are 300% over inflated. Do the experts care? Are they explaining this truth to you?

Does it really matter?

Australian Road Transport Suppliers Association (ARTSA) did some stopping tests, working with the NHVR several years ago. ARTSA proved that a lightly loaded semi, with the correct tyre pressure for the load, stopped 15% shorter.

Last year, ARRB did some tyre performance tests for me. These proved that a 20% over inflated tyre’s slip angle increases 15%! Our trailer tyres are 85% over inflated, at best. How much do those tyres slip? How much do they wag their tails when they are empty, with 300% over inflated tyres

Tyre pressure tests done in the USA proved that suspension wear and tear increased 85% with over inflated tyres. That means your suspension is being hammered 566% higher than it would be if the tyres were inflated to match the load. These over inflated tyres are hammering out roads into the death traps they are now.

Over inflated tyres act like super balls, amplifying any road roughness, hammering our trucks and drivers into an early grave, or years of suffering. Does anyone explain the dangers of incorrect tyre pressures? Why not?

Trucks with the wrong tyre pressures are harder to drive, increasing driver stress, wearing him out. Add in high vibration, poor handling, and a rough ride and it is no wonder that drivers are suffering.

The tyre manufacturers and retailers are making a lot more money than they should.  Optimising tyre pressures, especially with CTI, eliminates most blow outs, most uneven tyre wear, and adds at least 30% longer tyre tread life. Optimised tyre pressures increases casing life by at least 15%, saving more money.

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