It’s common knowledge that the right tire inflation pressure is a major factor in vehicle safety, tire life, fuel efficiency and operating costs, say officials with Bendix Commercial Vehicle Systems (CVS). Less frequently discussed is the specific issue of pressure imbalance in dual tire wheelends.
Bendix CVS (www.bendix.com) develops and supplies leading-edge active safety technologies, energy management solutions and air brake charging and control systems and components under the Bendix brand name for medium and heavy duty trucks, tractors, trailers, buses and other commercial vehicles throughout North America.
A Negative Impact
A low-pressure tire can have a significant negative impact, and it doesn’t take much less air to start accelerating wear, says Jon Intagliata, product manager, tire pressure monitoring system, Bendix. Tire underinflation by as little as 10 percent results in a 1.5 percent drop in fuel economy, and underinflation by 20 percent results in a 30 percent reduction in tire life.
“Add in the fact that safety components – ranging from brakes to stability and collision mitigation systems – can’t perform to their optimal capabilities if tires are not operating in their proper condition, and the stakes become even greater,” Intagliata notes.
Bendix “highly recommends” the use of a tire pressure monitoring system (TPMS) to provide fleets and drivers with real-time information and alerts, enabling them to address potential failures before they occur.
Imbalance
A dual tire arrangement requires additional care, and close attention should be paid to keeping both tires inflated to the same pressure, Bendix’s Intagliata advises. If the pressure between both tires is not equal, one tire will wind up carrying a greater share of the load and do more work than the other. Because their sizes will be slightly different, as the tire assembly rotates, the smaller tire will drag, causing premature wear.
“In short, running imbalanced duals increases the odds of a blowout on the overloaded tire and significantly shortens tire life on the underinflated tire,” he says. “Industry data has shown that the pressure difference at which this becomes an issue can be as little as 5 psi. This small difference in pressure creates a difference in the tire’s circumference and causes the smaller tire to be dragged by the larger tire, producing accelerated or irregular wear.”
While addressing dual tire imbalance is simple enough – it’s just a matter of setting the tires to the right pressure, which is routine maintenance – noticing it in the first place can be trickier, Intagliata points out. This is especially true for the inner dual which is masked by the outer tire, making it very difficult to spot a problem.
TPMS
The best tool for tracking proper tire psi is a tire pressure monitoring system, says Intagliata of Bendix. While these vary in design, they operate in the same general fashion, using sensors mounted at each wheelend of a tractor or trailer to constantly measure a tire’s pressure. If the sensor is mounted inside the tire, it can also measure temperature.
Tire pressure and temperature information is transmitted wirelessly and displayed on either an in-cab display or a technician’s handheld device during maintenance checks.
In the cab, most TPMS systems will provide pressure alerts to drivers, he says. Some, like the SmarTire TPMS by Bendix CVS, can provide temperature-compensated pressure figures, along with high-temperature alerts. It also includes a programmable alert that will let the driver or a technician know when a set of duals exceeds a set deviation in pressure between the two tires.
To monitor trailers, SmarTire Trailer-Link TPMS wirelessly transmits alerts, pressure and temperature information for trailers directly to the tractor and is displayed on the system’s TPMS dash gauge or integrated vehicle cluster.
“The more real-time information and alerts a system can provide, the better equipped a driver is out on the road, and the safer the truck becomes,” Intagliata says.
“Simply paying attention to the details of correct inflation, tire temperature and dual tire pressure balance can help keep vehicles on the road and in good operating condition, reducing the odds of a catastrophic failure and improving highway safety.”
