The Technology & Maintenance Council of the American Trucking Associations is upping the ante in the tire pressure inflation game. In an industry that struggles to get drivers to use a tire pressure gauge instead of whacking a tire with an axe handle, TMC is now saying that merely verifying a tire OE’s recommended pressure isn’t enough.
TMC's Future Truck Committee announced that it has directed its Future Tire Durability and Reliability Task Force to explore the feasibility of an automated system capable of monitoring and actively managing tire inflation pressures in commercial vehicle operation.
Based on the Task Force’s research, TMC says this position paper defines future features and expectations of such a system, and presents recommendations on operational capabilities, technology integration, and potential regulatory considerations. Such a system should be able to rapidly adjust tire inflation pressure based on changing tire load, temperature, vehicle, speed, and other conditions, so the tire is operated at the optimum pressure to maximize its performance.
According to TMC’s research, proper tire inflation pressure for the load being carried provides several key attributes necessary for safe, reliable and economical service. Among these are:
- Load capacity.
- Transfer of driving and braking forces from the vehicle to the road.
- Resistance to environmental conditions and aggression from the road surface.
TMC notes that establishing proper tire inflation pressure is typically based on the maximum likely load expected at each vehicle wheel position. Today, for the most part, the report says, tire inflation pressure is set at a fixed value based on the anticipated maximum tire load at highway speeds, but does not take into account the varying load, speed and environmental operating conditions actually experienced by the tire and vehicle.
There are tire pressure systems on the market today — generally known as tire pressure control systems (TPCS) or central tire inflation systems (CTIS) — that offer the ability to adjust tire inflation pressures for multiple sets of operating conditions, but they are not used outside a fairly narrow range of commercial transportation segments (such as agricultural, logging, and mining operations).
To address these concerns, a new paper authored by TMC’s Future Tire Durability and Reliability Task Force conceptualizes what a complete tire inflation pressure management system would be; one that takes a total vehicle systems approach to real-time inflation pressure management based on dynamic operational conditions. Such a system would require integration between the vehicle, environment, and tire/wheel assembly to determine the correct inflation pressure for each tire at any given moment. It would require the capability to inflate and deflate the tire as necessary to meet the actual tire operating environment.
In pursuing this new method of determining proper tire inflation pressures, the report says fleets would realize many immediately tangible benefits, including:
- Safety: Tires that are underinflated for the load being carried suffer from excessive sidewall flex and higher operating temperatures, which can lead to serious material degradation (e.g., circumferential rupture or “zipper condition” — a major cause of “rubber on the road”). Tires that are overinflated for the load being carried have less tread rubber in contact with the ground. Since the tread contact area is the sole physical interface between the road surface and the vehicle, all driving, braking and turning forces are transmitted through this area. Less tread rubber on the ground results in these forces being spread across a smaller amount of tread rubber. This potentially affects the vehicle’s ability to accelerate, decelerate, and respond to a steering force input. Overinflated tires are also more prone to road shock and impact damages.
- Performance: Tire manufacturers design their products to deliver many attributes, not the least of which are load capacity and tread life. Radial tires are designed to achieve a certain degree of sidewall deflection and tire footprint shape. Excessive tire inflation pressure leads to less sidewall deflection; the resulting smaller tire footprint can have a negative impact on through increased the tire wear and reduction in resistance to irregular wear. Insufficient inflation pressure for the load carried creates excessive buildup of heat in the tire, which will reduce its service life.
- Economy: Tire life can be measured in both tread mileage and cumulative casing mileage. Reductions in tread mileage from rapid or uneven tire wear directly impact total tire life cost. Incorrect tire inflation pressure costs money in the form of tread wear and casing life. In addition, tires contribute to total vehicle fuel consumption, and underinflated tires require more energy to rotate due to increased rolling resistance.
Based on this, TMC is now recommending the development of an integrated tire inflation pressure control system that can compensate for various operating conditions and provide an automated means of inflating and deflating each tire to match the conditions encountered.
Ideally, the TMC report says, such a system should be able to:
- Determine the load on each axle end then adjust inflation pressure for each tire to match this load. For tires in a dual configuration, the tire inflation pressure system should maintain a connection between the tires in a dual set to ensure they always have equal inflation pressure with the ability to be isolated in the event of a problem such as a rapid loss of inflation pressure.
- Compensate inflation pressure in all tires based on current ambient temperature and ambient barometric conditions resulting from altitude changes.
- Adjust tire inflation pressure when a vehicle is operating at lower speeds for a continuous period such as city driving or stop and go conditions. This should also incorporate vehicle speed monitoring with automatic inflation capability if the speed is exceeded above a preset level.
- Provide an immediate alert to the driver regarding adverse inflation pressure conditions, including an alert if either an unusual, unexplained loss of inflation pressure occurs, or if an unusually high increase in pressure occurs — e.g., more than 20% — caused by an outside heat source (such as a wheel bearing failure or dragging brake). These alerts should be visible to the driver as well as available for transmission through vehicle telematics to a central maintenance facility.
- Monitor tire inflation pressures when the vehicle (either the tractor or trailer) is not operating, in order to facilitate proactive tire maintenance. For combination vehicles – tractor and trailer(s) – integrate monitoring and inflation of all tires in the combined vehicle automatically after the coupling has been completed.
- For trailer operations, incorporate smart technology that is cognizant of loading and unloading during loading operations (i.e., weight transfer from forklift movement should be considered when designing a system).
- Provide capability for rapidly inflating and deflating a tire should positive or negative pressure adjustment be necessary. An interlocking system would require the minimum operating inflation pressure prior to operation. During operation, vehicle speed should be monitored and governed to respect the current operational tire load, with an immediate alert sent to the driver and the central maintenance facility when the inflation pressure is below the required inflation pressure for the current load.
- Be robustly designed, so critical hardware for such a system, such as air lines, air valves, mounting brackets and electronic sensors, are protected from corrosion and operational damage. Operational damage could occur from objects in the road could be thrown into the tire or wheel by other tires, or by the forces present during a tire rapid loss of inflation pressure event or blowout.
- Be designed to ensure that the quality of compressed air provided to the tire is free of contaminants and water.
Along with the capabilities listed above, such a technology should be easy to integrate into the fleet’s equipment and maintenance system, addressing issues such as compatibility between tractors and trailers; simple set-up and adjustment of key parameters; and ease of maintenance, with electronic diagnostic capabilities.
The TMC report concludes that a system that inflates and deflates tires based on the dynamic factors detailed above would be a significant change to the “normal” practice of inflating tires today and urges that consideration be given to how such a system would fit into the current, and future regulatory environment governing commercial vehicles and tires, since tire pressures checked during a roadside inspection could vary greatly from the tire’s sidewall maximum pressure marking depending on tire load and other conditions.