Tire Pressure Inflation System (tractor & trailer)

Proper tire inflation pressure is critical to the optimal operation of a commercial vehicle. Underinflated tires result in decreased fuel efficiency and increased tire wear. A 0.5-1.0% increase in fuel consumption is seen in vehicles running with tires underinflated by 10 psi. Having appropriate pressure reduces tire wear, increases fuel efficiency, and leads to fewer roadside breakdowns due to tire failures

However, studies show that:

  • About one out of five tractors/trucks is operating with one or more tires underinflated by at least 20 psi.
  • About one in five trailers is operating with one or more tires underinflated by at least 20 psi.
  • Nearly 3.5% of all tractors/trucks operate with four or more tires underinflated by at least 20 psi.
  • 3% of all trailers operate with four or more tires underinflated by at least 20 psi.
  • Approximately 3% of all trailers, and more than 3% of all tractors/trucks, are operating with at least one tire underinflated by 50 psi or more.
  • Only 46% of all tractor tires and 38% of all trailer tires inspected were within +/- 5 psi of the target pressure.

Automatic tire inflation systems (ATIS) work to overcome one or more of the causes of tire underinflation by monitoring tire inflation pressure relative to a pre-set target and re-inflating tires whenever the detected pressure is below the target level. The system alerts the driver that the tires are being re-inflated but does not report on the actual tire pressure. The system relies on the vehicle’s compressed-air tanks or draws air directly from the surrounding environment using a self-contained pump.

There are two types of ATIS. One system is a traditional compressor-based type that provide air pressure from the tractor to the tire. One version of this type uses internal pressurized axles like a trailer system while the other uses external air line routing under the fifth wheel around the tire valve stem. The other system is self-contained compressing direct atmospheric air and mounting on the end of the axle, generating its own air pressure at each wheel end position and connecting to the valve stem for either duals or wide based singles.

Approximately 15% of tractors and 85% of trailers are equipped with tire pressure inflation systems installed.

 

Benefits

The system keeps tires properly inflated, which reduces rolling resistance and improves fuel economy.

Operating on low pressure causes premature tire wear; by keeping tires properly inflated tire life is improved

Very low tire pressure can cause a tire to rupture causing a roadside breakdown. These systems keep tires inflated to their proper pressure level, and reduce roadside breakdowns.

The system eliminates the need for manual intervention in the event of low tire pressure.

The system maintains the tire pressure difference between the two tires in a dual assembly to 5 psi or less.

Tire condition can be monitored remotely via telematics.

Challenges

If drivers are overly reliant on a tire pressure system and start up the truck before inspection it is possible for tractor air fed tire inflation systems to pump up the tire before the driver inspects it, thereby masking the issue. Pre-trip inspections should not be replaced by technology.

Systems that use tractor air with externally routed lines to inflate the tires much have air plumbing that reaches over the outside of the tire to the wheel end.

Self-contained systems and axle air fed systems will accommodate the installation of aero wheel covers.

Self-contained solutions compress air as the tire is in motion.  Until the vehicle has traveled for while the tire(s) may not be operating on full pressure.

Not all systems are easy to implement on the front steer axle.

Tire Inflation Systems

Fleet Perspectives

Fleets are realizing that their current tire pressure maintenance practices, which typically consist of having drivers manually check tire pressure, are not sufficient to keep the tires inflated to their proper levels.

Most fleets interviewed recognize the benefits of proper tire pressure and are considering the adoption of technologies that better ensure that tractor and trailer tires are properly inflated.

Fleets also shared that that tire pressure inflation systems can offer enough value that they would consider retrofitting them on tractors and trailers which had enough life left in them to justify the expense.

Early adopters of tire pressure inflation systems include tankers, vehicles with high trailer miles and/or low trailer-to-tractor ratios and vehicles with duty cycles that have diminishing loads.

Decision-Making Tools

The NACFE team developed several decision making tools to help fleets make decisions about purchasing ATIS.

  • A technology selection chart was developed that identified the major characteristics of the various tire pressure inflation systems. The tool condenses an immense amount of information into a single matrix that can assist in the selection of the correct technology for the fleet.
  • The payback calculator allows fleets to input data and estimate the payback of various technologies based on their benefits. It calculates the benefits based on savings from reduced roadside breakdowns, extended tire wear, and improved fuel economy.
  • A Confidence Matrix that summarizes the study findings and indicates NACFE’s confidence in the various automatic tire inflation systems.

Manufacturers

Conclusions

The currently available commercial vehicle tire pressure inflation systems are reliable and durable. There are strong options for various truck duty cycles and fleet business models.

Manufacturers continue to develop system for improved performance, better reliability and lower overall costs. As systems become more available from the tractor and trailer manufacturers, the quality of the installation increases and costs decrease. This should lead to increased adoption of these systems.

Factors contributing to satisfactory operation of a tire pressure inflation system include:

  • Matching the fleet’s need with the specific capabilities of the various tires pressure systems currently available
  • Training personnel and developing internal operating procedures around the new tire pressure system
  • Seamless integration of the TPMS into the fleet’s day-to-day operation

Decision-Making Tools