Steady as she blows

Freightliner tractor with the Vigia Guardian external system installed.

How often do you check your tire pressures and pump them up? That is probably the single most critical factor in whether you can profit from using a tire inflation system. The more your tires run with improper pressure, the faster they wear and the more
likely you are to have downtime and service calls.

Many carriers are using inflation systems with good results, and it’s not just the big guys, either.

“We suffered from constant blowouts, underinflation, punctures and case damage,” writes Dennis Roohan of Farragher Logistics, an eight-truck fleet in New South Wales, Australia, in a letter to inflation system maker Vigia. “With the system, these problems were immediately rectified, and we have gradually seen an improvement in our tire wear and fuel economy.”

Harold Leiss, owner of Kirk National Lease in Sidney, Ohio, bought 50 Dana suspensions equipped with Dana Spicer’s inflation system in 2002. Since then, he reports no failures and noticeable improvement in tire wear, says James Beverly, a chief engineer with Dana. Leiss recently placed an order for 50 more systems.

Preventing tires from falling significantly below their rated pressure saves money in various ways:

FUEL CONSUMPTION. Less heat is generated by a fully inflated tire, so rolling resistance is much less.

TREAD WEAR. Low tire pressure, even 6 or 8 psi, means the tread doesn’t sit flat on the road; it also squirms and scrubs unnecessarily. Excessive flexing of the tread and sidewalls causes deterioration of cords and other tire materials. In effect, you are burning extra diesel to destroy your tires. In operations where tires are retreaded, not replaced, otherwise usable casings may be destroyed.

SERVICE CALLS. Many inflation systems not only counteract normal leakage but keep a tire with a significant leak properly inflated, allowing you to get home or to a service facility.

Vigia customer Walter Vicente, who owns and operates four-truck Vincent Lines of San Bernardino, Calif., saw this benefit when he tried to get a nasty puncture repaired while on the road, says Vigia executive Ken Siler. Vicente was told he would need a new tire for $350. He drove home to a familiar shop, where the tire was repaired for much less.

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PARTS. By reducing heat at every wheel position, a tire inflation system can increase the life of brake linings, brake drums and wheel bearings.

INSURANCE. Inflation systems also can reduce the chance of a wheel-off, a potentially expensive and dangerous accident.

Inflation systems on the market vary widely in price and complexity. Many are designed to work only on trailers because in large fleets maintenance is much harder to track properly in trailers than in tractors.

All systems derive their air from the brakes rather than having their own compressor. For this reason, all have a protection valve to ensure that brake pressure is preserved in case of a significant tire or inflation system leak. Check valves ensure that one tire with a large leak will not deflate the others.

Some inflation systems have additional filtration to keep dirt and grit out of the valves.

With an effective and properly maintained brake air filter/dryer, there should be little or no debris in the brake air, anyway.

Five leading inflation systems
The Airgo costs about $2,000 for three trailers. A do-it-yourself mechanic can easily install it, says Greg Alvarez, Airgo sales director. Air is delivered through either the trailer’s hollow axle housing or pressure tubing (your choice), then through the axle hub assembly and into the tires. A warning light lets the driver know when the system is delivering air to a leaking tire.

Required maintenance includes regular checks of hoses delivering air from hub to tire to ensure they are secure.

The ArvinMeritor PSI costs $700 to $800 and can be easily installed by someone accustomed to working on large vehicles. Manuals are available on the company’s website. Air is routed through a control box, then to each tire through the axle and a rotary union at the spindle end. An indicator light tells the driver of any excessive loss of air pressure.
Recommended maintenance includes a routine inspection of tires and wheel ends. The only moving part is the rotary union at each wheel.

The Dana Inflation and Monitoring System costs $600 to $850, including installation, depending on the trailer manufacturer. It also can be retrofitted.

An electronic control unit and pressure sensor measure tire pressure. A solenoid-controlled manifold controller depressurizes rotary air seals and lines when not inflating, which increases seal life and helps prevent leak-down. The system warns only when tire pressure is below a preset level, which avoids false alarms at startup. Stainless steel braided hoses eliminate axle pressurization that can cause rust and scale. The absence of venting at the wheel-end eliminates risk of water ingestion, hub pressurization and seal blowout. The system can be integrated with Bendix TABS6 ABS.

There is no scheduled maintenance. In rare cases, replacing the air filter on the manifold may be necessary.

The Hendrickson Tiremaax is an option on Intraax and Vantraax trailer suspensions. Hendrickson declines to estimate a retail price; the system is installed only when the trailer is built.

Tiremaax is governed by an electronic control unit that detects low pressure and signals the operator if the leak is significant enough to require attention. The ECU responds with air from the trailer air tank whenever the inflation pressure drops below the setting. Air travels from the supply tank through air lines inside the axle to the wheel ends. A bolt-in, ball-bearing rotary union allows the air to flow through the spindle to the rotating hubcap fitting. Hoses with braided stainless steel jackets conduct air from the hubcap tee to the tires. A guard around the tee fitting protects it during tire removal and reduces potential damage when drivers use the wheel hub as a step.

A signal light notifies the driver of system status and maintenance requirements. As with most other designs, check valves help prevent tire pressure loss back through the system. If necessary, manual fill and pressure checks may be accomplished by unscrewing the hose end.

The Vigia Tire Guardian comes in an internal system for hollow-axle trailers and an external system for all vehicles with solid axles, including straight trucks and tractors. Installed, it costs about $1,200 for a trailer and $1,800 for a tractor. Special training is required for proper installation, says Ken Siler of Safer Corp., the exclusive U.S. distributor.

The internal version uses the trailer’s air brake system, tapping into the air supply tank. These hoses run to a control panel where sensors and valves control the pressure, allow calibration and refill the tires when a leak occurs. From the panel, the hoses that supply the tires run under the chassis and then, via drilled holes, through the axles. They run out of the hub, through the spindle, through a rotor that fits on the spindle, and on to the valve stem.

Two safety valves shut down the system if air pressure is lost. The trailer control panel, visible from the driver’s mirror, has LEDs that indicate system status.

The external version is similar, but the control panel sits inside the vehicle and includes gauges as well as LEDs. Each axle has its own gauge, sensors and valves and can be calibrated separately. This way, the steer axle can be set at a different pressure from the drives. The rotors on the external version are mounted differently, with rugged arms.

Required maintenance consists mainly of replacing the rotors every 100,000 to 150,000 miles, which the company says requires no special tools. The hoses leading from rotors to valve stems should also be inspected – though with steel braiding, they should require little attention.

Inflation systems can save a lot of money in a large fleet with salaried drivers, mechanics and a large fleet of trailers that are difficult to track. Less certain are the savings if you own only one or two trucks, especially if you keep your tires within a couple psi of the rated pressure.

Of course, some benefits cannot be easily quantified. A system that compensates for a leak that otherwise would create a dangerous low-pressure situation can be a life-saver. A system that allows you to make your delivery and get to a friendly repair location, thus eliminating an expensive road call and irritated customers, is worth a lot. Another justification is the one used to explain a gorgeous tractor with a big sleeper and all the chrome: It improves the quality of your work life.

Considering a measurable return on investment, however, a tire inflation system can pay off for an owner-operator in less than two years.

Nitrogen: Inflation’s gold standard
Believe it or not, plain air isn’t the ideal substance for filling tires. Nitrogen is best because its molecules are large and therefore will leak only a third as fast, says Ingersoll-Rand, which makes a nitrogen tire-filling system.

Nitrogen also is inert, so a leak won’t cause corrosion. Where air leaks through a casing, on the other hand, the combination of oxygen and moisture can speed deterioration of rubber compounds or even the steel cords.

A nitrogen inflation system essentially consists of a membrane that can filter out gases in air coming from a shop compressor, leaving only pure nitrogen for the tires. Such a system is far too expensive for a small operation.

However, you may find that nitrogen inflation is available at a tire shop or truck stop. Using nitrogen could help keep your tires nearer their rated pressure, thereby saving as much as an on-board inflation system would.

(248) 435-1000

Airgo Systems
(877) 550-6111

Eaton Corp.

Hendrickson International
(630) 910-2800

Safer Corporation
(415) 898-2000

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