Almost every fleet manager (I know of no one who doesn't) recognizes the major impact tires have on efficient operations. Tire maintenance, or the lack thereof, represents the greatest vehicle operating expense behind fuel.
When it comes to tire care, there is one aspect that counts more than any other: proper air pressure. It's the key to success. Of all the components that make up a tire's structure and contribute to tires operating as they were designed to, air is the most critical. Without sufficient air, a tire can fail, and its failure can be catastrophic in the short term, and costly in the long-term.
When air is confined to the inside of a tire, the assembly becomes a structural component to the vehicle as well as an operating element. The inflated tire becomes an extension of a truck's suspension. The sidewalls are designed to flex the casing to contain air and hold a particular shape when loaded to design capacities.
A properly inflated tire enables the tread to contact the pavement or ground in a certain way, and allow the proper amount of energy to be transferred from the powertrain, enabling vehicle movement.
When a tire is under-inflated, flexing of the sidewall increases. When inflation drops to about 20% of recommended levels, flexing becomes excessive. This unplanned movement creates unplanned friction between the metal strands and the encapsulating rubber. In time, the friction can generate internal heat in the tire's sidewall that is hot enough to melt rubber where internal components bond together.
You can demonstrate this by repeatedly flexing a paper clip. Bend it rapidly and it breaks. If you touch the point of fracture, you could burn yourself. The same things happen to tire cords in belts and sidewalls.
Have you ever looked at the strips of tire rubber along a highway? If you see wires, those are probably not recaps. These fragments are from treads that separated and were thrown because of under-inflation and heat build-up.
Less dramatic, but still costly in the long-run, are reductions in fuel economy and tread life caused by under-inflation.
How does your own fleet measure up when it comes to tire inflation? According to the Federal Motor Carrier Safety Administration, 7% of truck tires were under-inflated by 20 psi or more. Just as worrisome is that only 44% of all tires were within 5 psi of their target pressures.
The cost of under-inflation
The smaller the fleet, the greater the likelihood the tire is under-inflated. According to the Technology and Maintenance Council's Recommended Practice RP235A, “Guidelines for Tire Pressure Maintenance,” under-inflation is responsible for about one road service call per truck per year. The group also estimates that improper inflation increases total operating costs by $600 to $800 per truck annually.