UNDER PRESSURE
Making Road Gators An Endangered Species
Mark Putz
Associate Editor
Trucking escaped entanglement in the U.S. TREAD Act, but many in the industry predict future legislation covering tire pressure monitoring. Such laws may not offer any real safety or efficiency gains, but until tire failure is a thing of the past and road gators are driven to extinction, bureaucrats will scribble new regs.
Regardless of what comes down the legislative pike, more fleets than ever are getting serious about tire pressure.
Traditionally, inflation status was checked during normal weekly and monthly PMs, with drivers handing the daily and in-route checks. Of course, thumping a tire to determine proper pressure is about as effective as kicking the fuel tank to determine how much diesel you have. And while arming drivers with properly calibrated tire gauges is a step up from clubs, fleets are moving to monitoring systems. There are many systems on the market that monitor tire pressure on a real-time basis under varying environments.
What's Out There
A simple, visual form of pressure monitoring is offered by Monitortire, maker of Safety Caps. These valve stem caps display green when the tire pressure is adequate, yellow if tires are about four pounds underinflated, and red when they are around 10 pounds underinflated. The company touts the system's low cost and ease of use.
More accurate and inclusive systems use tire sensors attached to the rim of each tire. The sensors monitor air pressure and compensate for temperature changes. The sensors send an RF signal to a computer that can display the information in the cab.
For example, SmarTire offers a system that features a transmitter with a strap mount configuration. The transmitter snaps into a flexible cradle design. The company says its Interrogator Wand activates the transmitter and eases receiver programming. SmarTire recently announced that it signed a co-development and marketing agreement and a supply agreement with Haldex Brake Products. The companies will engage in a joint development program to integrate SmarTire's system with Haldex's brake systems.
The Eaton Tire Monitor also adapts radio-frequency technology and in-tire pressure sensors to alert the vehicle operator to loss of tire pressure. A "check tire" light signals the driver that air is needed - before the tire is in danger of being destroyed or can no longer be safely repaired or retreaded.
Eaton offers independent tire monitor systems for tractors and trailers, eliminating a need for "married" vehicle combinations. Unique codes for each tire sensor programmed into the receiver assure that the system only monitors tire pressure information for the vehicle on which it's mounted. The system features Schrader-Bridgeport sensors that replace ordinary valve stems, and can be programmed to monitor tires with "cold" pressure settings up to 125 psi.
The Tire Mate 2000 likewise features a small wireless transmitter. It weighs less than half an ounce and is attached to each valve stem. If inflation pressure falls below the trigger pressure, a signal is sent by wireless transmission to a display module in the cab. The driver is alerted with an audible alarm, while a flashing light displays which tire is losing pressure. Each tire is assigned its own pressure transducer (sensor) with a signal code that identifies each tire to the display module. Sensors are pre-set at the factory for recognized tire pressure ranges, and are powered by a battery pack designed to last for 12 months before replacement.
Dual Dynamics offers Crossfire, a dual-tire pressure equalization system. The company says the product also has a feature that automatically isolates the good tire in the event of a failure. When a blowout occurs, the internal safety valve closes immediately with only a slight loss of pressure to the good tire. In slow leak situations, the valve isolates other tires after a pressure drop of about 10 psi.
Also on the market is the Meritor tire inflation system by Pressure Systems International (PSI). This system automatically monitors and maintains inflation levels. The system dispenses as much air as needed to keep a tire inflated until service can be performed.
Michelin's eTire system incorporates what it calls an InTire Sensor, sidewall-mounted SensorDock, hand-held or drive-by reader, and Bib Track software to capture and report tire pressure, wheel position and maintenance information. The information gathered is reported in a fleet specific manner via an Internet server to enable maintenance managers to track tire costs and monitor inventories.
The InTire Sensor provides tire identification and tracking as well as real-time monitoring of tire pressure and temperature. The sensors are mounted inside a tire on the inner liner, using the Michelin SensorDock. The InTire Sensor uses a capacitive MEMS (micro electro mechanical systems) device to sense pressure and temperature.
Hand-held or drive-by readers installed at fleet depots or truckstops are used to wirelessly communicate with the sensor to read the digital pressure, temperature and identification information.
On the OEM side, Peterbilt now offers a new four-channel tire pressure control system built by Dana Spicer. The Tire Pressure Control System (TPCS) allows operators to increase and decrease air pressure in the tires using an in-dash console, adjusting traction to best meet application and surface conditions. The four-channel system provides each tire with an independent inflation/deflation valve, so loss of air to one of the drive tires won't disable the vehicle. The system is geared toward vocational applications such as mixer, rescue, dump and logging.
The price of a pressure monitoring system can be justified for a number of reasons. For example, a truck starts a long haul with the correct tire pressures. But changes in weather, temperature and small leaks take a toll, leading to a loss of tire pressure. Thus, tire pressure monitoring offers a direct cost benefit with improved fuel economy, reduced down-time and an increased return on your tire investment.
