You may have heard that Tire Pressure Monitoring Systems (TPMS) when used properly, can save fuel, increase tire life, and improve safety. Previous work by the Federal Motor Carrier Safety Administration documented the following effects of improperly inflated tires.
- Reduced fuel economy
- Increased chance of tire blowouts
- Accelerated tire wear
- Increased road debris
- Increased roadside assistance calls to repair tires
The above items increase expenses. Items that result in the truck being out of service also may reduce revenue. However, to maximize your return on investment, it is important to understand the types of TPMS, and the advantages and disadvantages of the different types of systems. The goal of this article is to help you choose the tire pressure monitoring system that best fits your budget and type of operation.
Things to consider in your evaluation:
- Type of TPMS
- Battery – life and ease of replacement
- Ease of installation
- Ease of use
Types of TPMS
A tire pressure monitoring system will alert a driver if pressures are outside safety perimeters or pressure set points. The system will work directly or indirectly, by either directly reading the actual tire pressure or indirectly estimating the relative tire pressure. Heavy vehicles like dump trucks typically use TPMS that directly reads tire pressures. There are five types of direct reading tire pressure monitoring systems for heavy vehicles:
- Rim Mount
- Tire Patch
- Interior Valve Stem
- Valve Mounted (Flow Through)
- Stem Mounted (Not Flow Through)
All TPMS have similar functions with the same basic component categories: Sensor/Transmitter, Receiver/Gateway, and the Driver display. The components can vary in internal or external mounting, antennas, battery life, airflow design, and cost.
Rim Mounted systems have antennas installed inside the tire on the rim of the wheel. The Tire Patch system is also mounted inside the tire but with the antenna mounted on the interior of the tire itself.
- Reads both pressure and temperature
- Better early detection of low pressure
- Less susceptible to environmental damages
- Complicated installation
- The tire must be removed to replace the sensor
- Sensors can be damaged during installation or tire change
The Interior Valve Stem system has the sensor mounted on the valve stem inside the tire. Exterior Valve Mounted systems are installed on a modified valve outside of the tire.
- Easier to change the sensor battery
- Easier inflation of tires
- Easier installation of components with multiple sensor options
- Shorter sensor battery life
- Valve component long and heavy
- Weight may affect wheel balancing
- Damage to valve component may cause air leakage or may restrict filling tires
Stem Mounted systems have screw-on sensors that go on the end of existing tire valve stems.
- Easy installation
- Short, lightweight sensors
- Longer sensor battery life
- Hard to install on rims with small holes
- Sensors are more easily damaged by debris
- Must be removed to add air to tires
Connect to Telematics
Real-time monitoring of driver behavior and vehicle safety is a premium feature of vehicle monitoring systems on the road today. TPMS Manufacturers like Valor, Continental, Doran, and Pressure Pro integrate with companies like Geotab, an industry leader in fleet tracking platforms. These tire pressure monitoring systems transmit real-time data, to the vehicle operator through a dashboard display and, also through the Geotab telematics device to a server. The data can then be monitored by the home office to notify of potential issues with tire pressure and temperature.
Real-time monitoring also removes the need to do manual inspections. These integrated systems help companies maintain high safety standards, avoid unnecessary costs associated with tire replacement, track fuel expenses, and assist owners with predictive maintenance of their fleet.
Cost of Improper Tire Inflation
Increased Fuel Cost
Every 10% reduction in pressure results in approximately 1% reduction in fuel. A truck travelling with tires 10 psi low on average is wasting $200/year in fuel alone. According to an FMCSA study, only 44% of truck tires were within 5 psi of their target pressure. 7% were off by more than 20 psi.
Increased Tire Wear and Uneven Tire Wear
Underinflated tires increase tire wear-related costs by approximately 12%. This works out to $200/year on average for a typical dump truck.
Increased Tire Blowouts
In the FMCSA 2006 study, there was on average, 1 blowout per 18 tires in a year. Add the cost of a service call and the lost production to determine this cost for you. These blowouts also contribute to roadside debris which can cause others to have an accident trying to avoid the debris or from hitting the debris.
Under-inflated tires can change the handling and increase the braking distance, increasing the chance of an accident. Obviously, these accidents result in a reduction of income when the trucks are unavailable to work. They also increase expenses due to the repair costs.
Increased Legal and Insurance Costs
Tire blowouts and accidents resulting from tire issues can get very expensive when they result in legal battles. Increases in accidents also raise your insurance rates.
Cost of Manual Inspections
The approach that most companies take to keep their tires properly inflated is to rely on the drivers to check their tire pressures before they get in the cab. Doing a manual tire inspection as part of the DVIR is certainly sufficient but can be time-consuming. Using a pressure gauge to check the pressures of ten tires on a triaxle truck is no quick task. On average it may take your driver 10-15 minutes to measure the pressures for one truck. At 5 inspections a week for 52 weeks, this cost works out to $780 per year if the drivers are paid $15 per hour. This cost analysis is for one truck. Most dump truck companies run with several trucks in their fleet. A company with 20 trucks will spend $15,600 annually in labor costs alone, to simply comply with DOT regulations doing manual tire inspections. (This analysis includes only the time needed to check the tire pressures not the time it would take to fill the tires with air.)
In addition to the time required to properly check the tire pressures, you must ask whether the tires are truly getting checked before the driver gets in the cab. According to the FMCSA numbers, this approach has not proven to be very effective since only 44% of tires tested were within 5 psi of their target pressure.
Top Rated Systems
The table below shows system features for 4 top-rated tire pressure monitoring systems for heavy vehicles. This is not meant to endorse the 4 below, nor to suggest that these are your best options. The goal of the below chart is to give you a starting point when evaluating TPMS. You can compare these features and prices to the systems you find to evaluate.
Below are videos for the above-referenced tire pressure monitoring systems.
Paul A. Grygier and Samuel Daniel, J. –N.-T. (2010). Tire Pressure Monitoring Tests for Medium and Heavy Trucks and Buses. Washington D.C.: National Highway Traffic Safety Administration.