Air as needed

Being full of air is not a good thing for, say, a politician. But it's a very good thing for a tire. Keeping tires chock full of air has always been of concern to fleet managers knowledgeable about what runs up tire costs. Certainly few care more about this than managers responsible for trailers that roam the country and seldom get back to a fleet's own yard. Those operators have been the first adopters

Being full of air is not a good thing for, say, a politician. But it's a very good thing for a tire. Keeping tires chock full of air has always been of concern to fleet managers knowledgeable about what runs up tire costs.

Certainly few care more about this than managers responsible for trailers that roam the country and seldom get back to a fleet's own yard. Those operators have been the first adopters and continue to be the most likely to buy automated inflation systems.

But new federal regulations on the horizon — courtesy of politicians reacting to the light-truck/tire failure fiasco that had originated with a rash of horrific tire blowouts on SUVs — may pump up fleet interest in buying automated tire — inflation systems.


The law, known as the TREAD Act, is a far-ranging piece of legislation. But it will directly affect truck fleet owners only by a requirement — yet to be finalized-calling for onboard devices that warn when tires are dangerously under inflated.

As luck, or in this case technology would have it, automated tire inflation systems already accomplish that function just as stand-alone tire-pressure monitoring systems do.

Of course, fleets that can manually check and air their tires frequently in their own yard or under contract maintenance may only need an onboard monitoring system when the law requires it.

But that's ok with the suppliers of automated inflation systems. Their sales pitch goes like this: why not have a system that not only indicates when the air is low but puts the needed air into the tire, then and there?

If sold on that pitch, the next step is to get educated on the features and stated benefits of the various automated inflation systems now available.

Be assured they all put the proper amount of air in truck tires without human assistance and they all promise relatively rapid paybacks.

A key distinguisher is whether they are described as constant or non-constant pressure systems. It would be nice and simple to be able to say one type of pressurization is better than the other but each supplier has their own rationale for their product engineering and these should be absorbed before making a purchase decision.

But bear in mind that, as one engineer puts it, using one or another automated inflation system is better than not using one at all.

According to Varun Rao, product manager for the Meritor Tire Inflation System (MTIS) by P.S.I., the customer base for inflation systems is wide. He says intermodal chassis fleets were the first big users, due to how seldom they get to touch their tires. But he says that especially over the past two years, sales to linehaul truck fleets have increased.


“Tire inflation is moving from a discretionary cost to almost a must-have product for many fleets,” asserts Rao.

Rao says automated inflation systems offer a number of advantages. “They take the uncertainty of dealing with tire failures out of drivers' hands and reduce the expense of road calls and downtime.

“Return on investment (ROI) is the key,” he states. “Our trailer-axle system has been in the market for five years and we've published results that show payback for various fleets of less than 12 months.”

Rao says that trailer or chassis OEMs usually install MTIS but retrofits can be done. He says ArvinMeritor/P.S.I. has “product for steer and drive axle positions under development right now.”

According to Rao, MTIS is a constant pressure system that keeps tires continuously inflated. As for whether this constant pressure is tough on seals, he says the system now features a new compound for the O-ring seal that resists slicing. As a result, the system's warranty has been upped from two to three years.

Rao says TREAD Act requirements likely will call for monitoring that indicates whenever tires are at least 10% under-inflated.

“MTIS exceeds that ability,” says Rao. “If 2 PSI or more are lost, our indicator light will come on — and the systems will keep the tire inflated unless, of course, there is a full blowout.”

Rao says that beyond automatic monitoring and inflation, for a small “up charge” MTIS can be tied in with a trailer GPS system. “Some fleets request this so they can track the tire pressure signal, too. We can set that up for them easily.”

Tony Ingram, president of Airgo Systems, says his firm's system is new to the market and is designed to take automated inflation “to the next level” of development.

He says the “big issue” for fleets isn't so much using a system but deciding which system will save them the most money with the least negatives.

Ingram says Airgo is a constant-pressure system with a check valve that continually senses pressure and opens as needed so air will flow into the tires.

He says that the seals are made of carbon graphite and hardened steal to stand up to the pressure. According to Ingram, the system is fully mechanical and pneumatic, requiring electricity only to power the warning indicator light for lost inflation.

While Ingram says Airgo can keep a tire inflicted with a sizeable hole inflated thanks to its high cubic capacity, he says “most truck tires are destroyed over time by a low-pressure leak.”

Ingram says a key feature of the Airgo system is that it does not vent through the hubcap as some systems do. “Every rotary seal, even ours, will weep or leak air,” he explains. “Ours leaks a lot less than a lip seal and it leaks into the atmosphere. We feel that is better than sending it through the hub and then venting from the axle. That approach risks pressurizing the hub and blowing out the rear seals. If that happens, you lose the oil and burn out bearings.”


The Airgo system is available both as an OEM option or a retrofit. As for future offerings, Ingram says a drive-axle system prototype is being tested. He also notes Airgo is “looking at technology to further improve the product and keep making it more user friendly.”

According to Jim Beverly, chief engineer for advanced chassis control, the Dana Spicer Tire Maintenance System (TMS), which is marketed by Roadranger, is an active but not constant-pressure “smart” system controlled by a microprocessor.

“Unlike a regulator-based system, ours does not put continuous pressure on the seals and lines, which can wear them down,” he remarks. “Instead it checks each tire at startup and then every 10 minutes, inflating them as needed.” Beverly notes the system's programmable inflation threshold can be set at a 10% or 20% below optimum pressure.

“TMS has a sealed wheel end,” he points out. “The system uses an axle tube to vent externally. Since we don't vent through the hubcap, water can't get in if the trailer is positioned in a dock area that's submerged.”

Since TMS is a computerized “smart system,” Beverly says it offers data links for transmitting tire information via satellite-based communication systems to warn of problems or schedule maintenance.

Beverly says TMS is offered only for trailer use and system purchasers cover a broad cross-section of highway operations, including tankers and fleets running wide single tires in place of duals.

The TREAD Act “has increased awareness but it's not having a major impact because buyers are looking at automatic inflation in terms of payback,” says Beverly “We expect our product will deliver ROI between 12 and 18 months.

“TMS will fulfill the expected TREAD Act requirements because it directly measures pressure with a transducer,” he continues. “It can warn of reduced pressure at the threshold that would be mandated.”

According to product manager Rick Bevington, Hendrickson's new TIREMAAX is “a smart system that comes with its own ECU to be as exact as possible with tire pressures.”


Bevington says the Hendrickson-designed TIREMAAX will succeed the existing Hendrickson Tire Inflation System (HTIS) which is based on Dana Spicer's product.

“TIREMAAX will also feature as standard several improved components, including stainless steel braided hoses,” he notes. “The system will check tire pressure every ten minutes.”

A key feature of the system is an indicator light that communicates information about the system.

“If up to 10 lb.. of pressure are lost, the system will work without notifying the driver,” explains Bevington. “If pressure falls below that 10-lb. threshold between the 10-minute cycle of checks, drivers will see the light activated. If the loss is severe — a blown tire — the system's logic will shut it down until the problem is addressed.”

Bevington says that TIREMAAX, like HTIS, is not a constant-pressure system. “Our years of experience as an axle and suspension supplier tell us that pressure kills seals in rotary unions because heat builds up,” he states. “To build a system that will last we use the ECU to check tires every ten minutes. And if a component inside the hub goes, you don't want the wheel end pressurized.

“Another nice feature,” he adds, “is we vent only through the axle to avoid pathways into the hub cavity, which should remain pristine.”

TIREMAAX will be rolled out in this year's fourth quarter and initially offered on Hendrickson's INTRAAX and VANTRAAX axles. Bevington says it may also eventually be offered on the aftermarket as a retrofit unit.

“For any system,” Bevington notes, “return on investment is specific to every fleet, based on the miles they run plus the number of road-service calls avoided. But ROI can be achieved within 18 months.”


According to Matt Reineke, president of PressureGuard, thanks to the TREAD Act “the Technology & Maintenance Council now has a focus group dedicated to tire monitoring/tire inflation systems.”

Reineke says fleets that “really know what their tire costs are” will see payback for inflation systems on trailers. “They eliminate any chances of operator error and keep the tires inflated at all times, not just on a routine basis as the trailer is stopped. They also inflate tires on trailers that have been ‘dropped’ or have sat for a while where they may have to be driven for an extended time under-inflated to get to a place where they can be filled.”

He says PressureGuard is a constant-pressure system and has “numerous features specifically designed to reduce long-term maintenance costs associated with other systems currently available.”

According to Reineke, these include a non-pressurized axle that avoids potential contamination that can lead to wheel end failures and potential failure of the tire inflation system due to clogged filters in the axle.

Other features include heavy-duty stainless steel braided air hoses with quick disconnects available to allow wheel end work to be completed without removing the inflation system and a specially designed hub cap that has integrated air channels with protective ribs to allow wheel end work to be done without removing the rotary union.

Remarking on whether steer and drive axle tire inflation systems will ever come into play, Reineke points out that “most trucks and tractors are in for routine maintenance on a regular schedule and their tires are examined much more often than those on trailers.

“As of today,” he continues, “inflate/deflate systems are gaining popularity in the construction industry where they are used to keep vehicles from getting stuck in sand, mud and dirt around the job site. These systems seem to be too expensive to show a real benefit to the standard fleets.

“We think an affordable drive and steer axle system that inflates only would be in great demand in certain industries such as refuse,” Reineke adds. “And if low enough in cost and maintenance requirements, it could gain popularity in [various] fleets.” He notes that PressureGuard does plan on developing such a system.

As it is, on-highway fleets have plenty of systems to choose from for automatic inflation of trailer tires.

The smart money would be on investigating fully the features, benefits and payback of each system before settling on one.

Tire talk

No major tire maker has yet introduced an automated inflation system for truck tires but they are naturally concerned with keeping tires properly inflated for maximum cost-effectiveness.

For example, Michelin last year rolled out its eTire System, an integrated electronic monitoring program for truck tires. It employs a special sensor mounted inside the sidewall to wirelessly transmit air pressure (compensated for cold-temperature equivalency) as well as wheel position and other maintenance data from each vehicle tire that can be read by either a dedicated handheld or permanently installed drive-by device.

Bob Benedict, senior R&D associate for vehicle systems, reports Goodyear is working with Siemens to develop a tire pressure and temperature monitoring system that is integral to the tire. “It will be a permanent way to track tires via a unique ID that can be written to,” he notes. The system will be marketed first to OE customers in the light-vehicle market to help them comply with the TREAD Act. “We expect the product launch for light and commercial markets will be from $05-'06,”says Benedict.

According to engineering manager Guy Walenga, Bridgestone/Firestone North American Tire is “in continuous development of an air-pressure monitoring system, and these efforts will certainly continue. We currently do not have a system available to the market,” he relates, “and like everyone else, the direction of our technology will be dictated by the TREAD Act.” Walenga points out “the same technology that is bringing trailer systems to market is at work for steer and drive positions as well.”

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