How Do The Automatic Tire Inflation Systems On Semi-Trucks Actually Work?

Semi-trucks are surprisingly loaded with technology, from cylinder deactivation systems that shutdown areas of the engine to save fuel to safety systems that announce when there are pedestrians, other vehicles, or bicyclists in the truck's blind spot. One of the lesser-known technologies is automatic tire inflation, which makes sure that the semi-truck's tires can be inflated in situations where the tire pressure has gone down.

Automatic tire inflation technology is not new, but manufacturers have recently put more of a focus on the systems they create. There are a number of well-known semi-truck equipment suppliers, such as Hendrickson and Cummins, that offer automatic tire inflation systems to customers.

The system that Cummins offers is called the Meritor Tire Inflation System, and the Cummins brand states it has been equipped on more than 1 million trailers. The MTIS also features "ThermALERT wheel-end heat-sensing technology" that will notify drivers immediately when wheel-ends begin to overheat. The Hendrickson system, TIREMAAX, claims that it will increase fuel economy, reduce tire maintenance, and reduce tire replacement costs.

While the process of keeping a tire inflated correctly sounds like a simple task, the way the automatic inflation systems work is slightly more complicated. According to Cummins, which is more known for its diesel engines, the MTIS system requires a hose that runs between the tanker's air supply to an air filter. From there, the air is then filtered through a self-draining filter to ensure there are no impurities.

The filtered, pressured air is then sent into a control box, which will regulate the pressure to whatever PSI the owner wants. Once the pressured air has reached the desired PSI, the air flows from the control box, through a hollow axle tube, and ends in the rotary union. A rotary union is used to transfer fluid from a stationary supply into a rotating machine. After the air is sent to the rotary union, the pressurized air is transmitted through a tire hose into the tires as needed.

The Hendrickson TIREMAAX system works similarly to the Cummins MTIS. Hendrickson claims that its rotary union is designed to last one million miles, and the filter at the supply port is serviceable to help ensure all the lines and seals stay clean and last as long as they can.

Tires that are inflated improperly can cause significant damage to your vehicle and can also potentially cause issues with other vehicles in extreme circumstances. Tires that are underinflated can bring fuel economy estimates down and limit the overall lifespan of the tire. Cummins claims its MTIS can extend a tire's life by 10%, which means less money spent on replacement tires.

According to a study carried out by the Federal Motor Carrier Safety Administration, using MTIS can increase a semi-truck's overall fuel economy by an average of 1.4%, again helping drivers save money. By having a system that constantly monitors your tire pressure and will add air pressure when needed, the risk of a blowout due to improperly inflated tires decreases.

Cummins will also provide maintenance and roadside assistance to owners of MTSI systems, making sure that its users are always able to get help when they need it. The company also claims that the typical return on investment for someone buying the MTIS is within one to two years, depending on the tire usage.