Trailer Tires Getting Neglected?
Automatic Inflation system keeps "em aired up on more than 300,000 vehicles.
ED THOMAS
CONTRIBUTING EDITOR
Even in the best-run fleets, trailers sometimes stay "out there" and are neglected. Maintenance is necessarily deferred, and tires — arguably the trailer's most sensitive component — fail sooner than they should, costing plenty in material, labor and service charges. Is there a solution?
Yes, say fleet managers who are using the Meritor Tire Inflation System by PSI. The system connects tires to a vehicle's compressed air supply and maintains pressure within a few pounds of a set level. PSI makes the system in San Antonio, Texas, and ArvinMeritor markets and services it worldwide.
Managers say flats and blowouts are all but eliminated, along with expensive road service calls. And tire life is appreciably extended. Savings in material and labor mean a quick payback of a system's cost.
A six-month return-on-investment is what's been determined by HEB Food & Drugs, a neighbor of PSI in San Antonio. That's based on the average road-service expense of $400, according to HEB's fleet maintenance manager, J. Xavier Olivo. HEB started testing PSI units in 1993. Early versions had problems, he says, but the latest systems are reliable, and have been spec'd on all new trailers for the last seven years. Thus most of its 1,100 trailers are PSI-equipped.
"Tread wear is improved by 15%," Olivo says. "And it saves considerable labor expense" because tires stay at proper pressure — 95 psi on duals and 100 psi on Michelin X-One big singles it's testing. "Before, five or six people would spend an entire week trying to check every one for tires," he says. "That includes some travel time," because trailers are based at the fleet's five terminals around Texas, but "we don't do that now."
The one downside, he says, is that "it is a mechanical system, so hoses and connections need checking. But we do that when we change tires, which is every six or seven months." HEB has 280 grocery stores in Texas, and all trailers return to a terminal each night. The average run is 280 miles.
PSI is an even bigger help to a long-haul fleet like PAM Transport, based in Tontitown, Ark. Carl Tapp, its director of maintenance, says almost 2,000 of the carrier's trailers have PSI because of the nature of its operation. Sometimes trailers are parked in out-of-the-way places and their tires simply are not checked like they should be.
"We'll drop off a trailer in some customer's yard, and when we go to pick it up it'll have picked up a nail in a tire or it'll have a leaking valve stem," he says. "Or maybe it's been sitting for a month in a mud hole. The driver signs off on an inspection, but you know he really hasn't done it."
It goes out onto a highway and soon a tire is flat and the vehicle's stopped at the side of the road. However, with the PSI, even a tire that's flat from a slow leak will be completely pumped up within a mile, Tapp says. The system eliminates what would be a road call, which results in much of the savings, plus saves the $300 tire and keeps it suitable for recapping, and extends its tread life. Because pressure is where it should be, rolling resistance is reduced and the tractor's fuel economy is better.
Tapp has been testing PSI's products since 1994 and now thinks the system is perfected. He specs it on all new trailers and installs it on older trailers where appropriate. Especially worthy of retrofitting are drop-deck vans, which run on small 17.5-inch tires subject to high loadings and high heat.
A careful analysis of tire expenses determined that PSI provides "an improvement in tire costs of 53%," he says. "This is a statistically correct study with three different trailer manufacturers — although that shouldn't matter — and three tire manufacturers," Tapp says. "It is a way of expressing savings without using dollar figures," which will vary with every fleet and become confusing in any presentation.
Railroads and steamship lines whose container chassis roam far from home were among the first converts to PSI, says Frank Sonzala, its executive vice president. Union Pacific, Florida East Coast, Burlington Northern-Santa Fe, Norfolk Southern, SeaLand and American President Lines are among the users on his testimonial list. He says over 300,000 trailers in more than 1,000 fleets now have PSI.
Depending on quantities and individual deals, a PSI system costs $600 to $700 installed on a new trailer. It can be retrofitted onto an existing trailer in a few hours. This includes drilling and connecting supply lines to the trailer's axles, which become tubes to carry air to the hubs, and thence via special fittings and hoses to the tires' valve stems.
Also installed is a control box with a regulator set at the factory to the pressure spec'd by the customer; a knob in the box also lets the customer adjust pressure himself. Other equipment includes a one-way check valve and self-draining filter, and special hardware in the hub to keep intact the system's integrity.
An indicator light on the trailer's nose tells the driver when the system is inflating a tire. Repeated light signals alert the driver to a problem tire, which he can report or have fixed. PLC4Trucks multiplexing can be used to activate an in-cab indicator light, and Waveburst satellite tracking is also available.
All popular wheel seals can take the PSI hub fittings, including a "rotary union" to interface the stationary axle with the rotating wheel. Any non-driven axle could be fitted with the PSI apparatus, but none have been sold for use on trucks or tractors, Sonzala says.
However, Meritor and PSI engineers are developing a tire-pressure maintenance system for power units, according to Varun Rao, ArvinMeritor's marketing manager for worldwide trailer products. It should be ready in a year or so.
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