Handling the heat

June 6, 2017
Precise tire maintenance is crucial in summer months

Gator season is here and nothing brings out the twisted shards of rubber and steel like the summer months. While the southern half of the continent must take precautions on a year-round basis, northerners get a little bit of a break until the sun starts getting higher in the sky. Radial truck tires are engineered to operate for hours at equilibrium temperature, where they emit as much heat as they generate.

When the internal temperature of the tire components exceeds that point, the bond between the belts and the body plies starts to break down, and eventually it results in a separation. Between the higher ambient temperatures and the mechanical heat generated by flexing sidewalls, the margin of error over the next few months is very small.

The obvious place to start is inflation pressure. For every 10-deg. change in temperature, the inflation pressure changes by 2 psi. In the winter months, the air temperature difference between the beginning and end of the day is not extreme because the lower ambient temperatures help cool the tires as they operate. Therefore, minor cases of under­inflation often go unnoticed because the temperature of the tire never gets hot enough to cause internal damage.

On the other hand, higher ambient temperatures in the summer do not create any cooling effect on the tires so the heat continues to build. In those instances, it doesn’t take significant underinflation to initiate the breakdown of internal components because there are no external cooling mechanisms.

“Drivers still believe they can bypass a calibrated air gauge when checking pressures.”

Around the turn of the millennium, the carrier decided to examine and find ways to better address driver fatigue. "We identified an opportunity that we could improve on fatigue management," LaCombe says, and the company began by focusing on things like shift consistency. A large portion of Dupré's business is slip-seat operations where "we look at getting a guy out [on a run] and back so the next guy can get on the truck," he explains, "and it's really critical that we try to have consistent start times and end times, which can help with your fatigue management and help a person's biological clock stay in tune."

Proper inflation pressure is critical year-round from a performance, treadwear, and rolling resistance perspective. Underinflation causes casing damage, irregular treadwear and reduced fuel economy. Despite the well-known negative effects of insufficient inflation pressure, drivers, and maintenance personnel still believe they can bypass a calibrated air gauge when checking pressures. It’s easy to find a flat tire with a club or hammer, but the combination of temperature differences and diffusion (the natural loss of 1-2 psi each month) often results in situations where all of the tires are equally underinflated. The only way to measure inflation pressure is with a calibrated air gauge.

Like most mechanical devices, air gauges are not all created equal. Inflation pressure gauges are not accurate for indefinite periods and in some instances, they are wrong out of the box. Companies that are serious about the proper inflation pressure must utilize master gauges or air pressure check stations to ensure the field gauges are accurate. Some of them are adjustable. Most are not. If the field gauges are not checked against a master on a regular basis, all of the extra effort can be wasted.

Technology is being leveraged with the increased use of tire pressure monitoring systems (TPMS) because the benefits of proper inflation pressure are realized on multiple levels. By notifying the driver when one or more tires are below the target pressure, downtime and increased tire costs can be avoided. Whether it’s the traditional electronic sensor inside the tire or an automatic tire inflation system (ATIS) that supplies a steady stream of air to the tires through the axle, monitoring the inflation pressure and warning the driver of a problem have a positive effect on tire performance.

Heat is the enemy and it must be treated that way, especially over the next few months. Drivers have to put away the “boot-o-meters” and pick up the air gauges, while maintenance personnel must understand that preventive maintenance requires a higher level of precision during the summer. Close may be good enough in December or January, but it won’t make the cut in June, July and August. An air gauge that’s off by 5 psi can cause a lot of problems when summer temperatures start climbing.

Inflation pressure maintenance is cost­ly and time consuming. Between the absolutely necessary inflate-through  valve caps and the labor alone, it’s going to be expensive. Throw in TPMS and/or ATIS and the costs keep rising, but the alternative is another summer of roadside failures, irregular treadwear, casing damage, and reduced fuel mileage. 

About the Author

Kevin Rohlwing

Kevin Rohlwing is the SVP of training for the Tire Industry Association. He has more than 40 years of experience in the tire industry and has created programs to help train more than 180,000 technicians.

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