Tech Talk

Doing it the old way costs you money

Doing it the old way costs time, money and limits your income. Whether you’re digging ditches, machining, welding, fixing your truck or transporting product. No one would dig a ditch with a shovel, or expect to be competitive without a CNC machine, or weld up something with oxy. 

I like old trucks but would never put one to work. Inefficient, low power and rag tyres. It just won’t work like a modern truck.

Running tyres ‘like we always have’ doesn’t work either in the 21st century. 100 psi in every tyre simply costs you too much. Safety is reduced, costs are too high, too many breakdowns, too much downtime and profits are missed.

In fact, running any truck without knowing your tyre pressure is like playing Russian Roulette. Your driver is flying blind. If your steer tyres are under-inflated, any further loss of air pressure, and you could have a deadly blow out. 

Fifty years ago, I purchased my first wide radial tyres. The tyre manager told me; “Radial tyres must ‘bag’ out or they can’t work.” Yet walk around your truck and look at the tyres where they meet the road. Do your tyres ‘bag out’? Your steer tyres will. But your drive tyres won’t. Look where the rubber sits on the road. How long is the flattened area? It should be about 200 mm. The flattened area on your steer tyres is most likely 230 to 250mm long (under inflated). Your drive and trailer tyres, in most cases, are simply round.  No flat spot. They are over inflated.

Often, you can actually see a slightly dirty section in the centre of the tread surface, with a clean section on either side (as pictured). Over inflated tyres lift the outer part of the tread off the road. It doesn’t even touch. But it does touch when road roughness or out of balance causes the tread to flex. This is when scalloping and outer tread wear occurs. In actual fact, the speed that the outer part of the tread is actually going is slower than the part that is touching the road. It just grinds the outer part of the tread away. Almost all uneven tread wear is caused by, or is amplified by, over inflation.

So, you are throwing tyres away. They are expensive. And then you sit still in the tyre joint getting new ones. More down time. 

Look at the Michelin tyre wear chart for drive tyres on Aussie roads. Twenty per cent over inflation wipes out 22 per cent of your tread life. Your casing life also drops.

Running the right tyre pressure with the right tools always adds at least 30 per cent to your tread life. And you get less punctures. And no blow outs.

Uneven tyre pressures in dual assemblies is universal. The inner tyre always runs hotter because of several factors. All of the engine heat heats up the inner tyre. The inner tyre surrounds the brakes. Axle flex and road camber increases the load on the inner tyre.  Unless the tyres have a system to ‘equalise’ the pressure, tyre wear increases. Bridgestone reported that a “5 psi (0.3 bar) difference in tyre pressures resulted in an 8mm difference in circumference, which leads to the larger tyre dragging the smaller tyre.” And, “Over a year, the under inflated tyre is dragged more than 1540 km.” This uneven pressure also wastes a lot of fuel.

It gets worse: If one tyre has 20 per cent more air pressure, the wheel bearing life is reduced by 40 per cent (Transpec).

“Over a life span of 1 million kilometres, a 20 per cent difference in pressure will add at least $600 to the operating cost. Increased fuel consumption will add at least $30,000 to the operating costs of each trailer. Poor inflation can reduce tyre life by more than 25 per cent, which adds at least $2,700 to the operating costs of each trailer.”  The same happens to the prime mover. Uneven tyre pressure will add at least $50,000 to the operating costs of a single trailer and prime mover.

It gets worse. Back in the 80s, there was a lot of research done by the Canada and USA.  Goodyear was involved. Strain gauges were placed on the drive axles. The correct, reduced tyre pressure reduced twisting strain “by at least 30 per cent.” This virtually eliminated axle and drive train breakages. Our customers report that diff and transmission life doubles.

Over inflated tyres hammer your truck and driver into an early grave. Over inflated tyres amplify every bump, costing you a fortune. Weyerhaeuser in the States reported to the Oregon Logging Conference that Suspension wear and tear reduced 85 per cent. Springs don’t break. Bushes last three times longer. Fatigue cracks in chassis are virtually eliminated.   Even suspension seats lasted 65 per cent longer.

Add in the fact that the correct pressure for the load reduces stopping distances and tail swing by at least 15 per cent. The truck rides better, handles better, is easier to drive, reducing driver stress. The right pressure is safer.

Okay, 100 psi in all the tyres costs an average semi rig $10,000 to $20,000 per year. Over the life of the truck, $200,000 is thrown away. If your truck works harder, or works in steep country, or on gravel or dirt roads, you’re wasting double the above.

So what is the correct tyre pressure? Weigh the axles to find out what your real axle load is. Look your tyre size up in a ‘Load to Inflation Table’. Run your finger across the weight choices until you find your weight. The correct tyre pressure will be directly above that weight. That is the pressure you need.  If the load changes, then the tyre pressure must change. There is only one correct pressure for each load.

I can’t change the pressures every time the load changes. Central Tyre Inflation makes it easy. Simply push a button on the dash display to change pressures. Dual tyres are automatically equalised at all times. The system automatically warns the driver if a puncture occurs, and automatically adds air, keeping your truck rolling, and your driver safe.

AIR CTI works on all axles.  It pays for itself in the first year, saving you time, money and risk.   Savings over the life of a heavy truck range from $100,000 to $500,000, depending upon the work the truck is doing.

And AIR CTI is guaranteed for 1,000,000 kms or five years.

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