Tire Pressure Inflation
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
Fuel Savings
The system keeps tires properly inflated, which reduces rolling resistance and improves fuel economy.
Increased Tire Life
Operating on low pressure causes premature tire wear; by keeping tires properly inflated tire life is improved.
Improved Safety & Fewer Roadside Breakdowns
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.
Automatic Tire Inflation
The system eliminates the need for manual intervention in the event of low tire pressure.
Balanced Pressure in Dual Tire Assemblies
The system maintains the tire pressure difference between the two tires in a dual assembly to 5 psi or less.
Enables Remote Monitoring
Tire condition can be monitored remotely via telematics.
Challenges
Poor Inspections
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.
Potential System Damage
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.
Wheel Covers
Because the system does not correct self-contained systems and axle air fed systems will accommodate the installation of aerodynamic wheel covers.
Movement Required for Inflation
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.
Steer Axle
Not all systems are easy to implement on the front steer axle.