In a properly inflated tire, most of a car’s weight is spread out evenly across the tire’s full width. When a tire is underinflated, the weight is concentrated on the tread, just under the sidewalls, which means the sidewall is running flexed and generating excess heat. Running like this reduces the vehicle’s handling and builds up significant heat caused by the excessive flexing, which results in premature tire wear and failure. Properly inflated tires can extend the life of tire treads by as much as 35 percent.
Kevin Krause, president of Ventech in the United States, shares some statistics from the Federal Motor Carrier Safety Administration. Tire-related costs are the single largest maintenance cost for a fleet, saying it costs about two cents per mile. For the average fleet in the United States, improper tire inflation increases the annual procurement costs for both new and retreaded tires by 10 to 13 percent. Also, improper tire inflation increases total tire-related costs by approximately $600 to $800 annually per vehicle.
Benefits of Proper Inflation
“If you see the tire debris on the side of the road, you see how people care about tires,” says Ulrich Pingel, owner and president of Ventech. He stresses, “It is important to see that every bit of debris is money and that it could be an accident.”
NitroFil owner Jay Lighter provides information regarding the safety concerns regarding properly inflated tires. Underinflated tires lead to tread separation and tire failure resulting in 40,000 accidents. Low tire pressure affects handling, stability and braking effectiveness.
Krause adds, “Your transit companies are on the cutting edge of safety and maintenance on their vehicles. The problem, however, is that up to this point, most people really haven’t looked at the tire issue, although it’s one of the largest costs for a fleet.” He adds, “A transit authority can not realize the benefit of having your tires
inflated properly — the emissions, the fuel, the safety — unless it’s checked every day. It’s a daily thing.”
For every 10 psi a tire is underinflated, the fuel consumption of the vehicle is increased by .5 percent. Vanessa Zaroor, director of marketing for Advantage PressurePro, explains, “You are having to use more fuel to overcome the added rolling resistance of the low tires. More than 2 billion gallons of fuel each year in the United States alone is wasted just because of low pressure.”
Pingel points out, “How they care about tire and tire pressure is changing because of the economic crisis, the fuel costs.” Being able to save 2 or 3 percent of fuel costs adds up over a year, and it has people listening.
Proper tire inflation also translates into cleaner air, Zaroor explains. Tires low on pressure release particles in the air from the tires breaking and the roadside debris. And, while properly inflated tires improve fuel efficiency, it also decreases carbon emissions.
Tire pressure monitoring systems
Detecting a potential situation before a vehicle is out on the road improves the safe operation of the vehicle and reduces operational costs. Despite this, tire maintenance procedures are often cut short and, in some cases, skipped.
Automatic systems make tire monitoring quicker and easier for agencies. Systems vary on how the information is captured and what is done with that information. There are several options available, including internal sensors in the tires, external sensors on the tire and external sensor plates, and with RFID technology pressure readings can be sent in various ways. One way to capture tire pressure readings is by an electronic sensor in the valve cap.
Zaroor explains how Advantage PressurePro’s monitoring system works. The sensor replaces the cap on your valve stem, an advantage being that there’s no professional installation required. The sensors send readings of the tire pressures and of the temperature codes to a monitor that sits in the operator’s cab and that information can be automatically sent to the maintenance office.
The system takes one to two minutes per tire to install and the sensors read 24/7, whether the vehicle is moving or parked. “Many systems only give you pressure readings once you’re moving at about 15 to 20 miles per hour, although by that time, you’ve already left your yard so you’re on the road and have to turn back around,” Zaroor says.
She continues, “We can give people and fleets the continuous tire pressure monitoring any way they want it.” That includes hooking it up to a telematic system or integrating it into a current telematic system. She also says they’ve worked with GPS companies to integrate their technology directly into that monitor so there doesn’t have to be a PressurePro monitor in the cab, as there are already so many viewables in the cab already. Zaroor adds, “It’s hard to break it down, to simplify it, because we do it so many different ways.”
Another system that attaches to the valve stem and monitors the pressure continuously is Fleet Specialties’ Tire Sentry Systems. Bill Shore, operations manager - tire pressure monitoring systems with Fleet Specialties, explains that the tire pressures can also be read by a handheld system in the yard. “That system is ideal for vehicles or fleets that come to the yard at the end of the day or where they’re doing a fueling station. They can be checked before they go out or when they come back.”
The handheld device can be pointed at a vehicle to get a pressure reading to detect any low tires. He says, “There are also the onboard systems where it will monitor tires from a panel. The most economical system for a bus fleet, however, would be the Yard Sentry handheld unit. All they would have to do is equip all the tires with the sensors and just have a signal yard monitor.”
The 360 HD is the monitoring system offered by Doran. It also has basically an over-sized valve stem valve cap that screws on the end of the valve stem and transmits the pressure reading through an FM radio signal. Chris Nau, Tire Pressure Systems – Truck, with Doran, says, “Our approach is to have the dash monitor display provide information to the driver with a limited number of moving parts.” He adds, “By keeping it all electronic, it really simplifies the long-term, wear-and-tear aspect of it.”
He also explains that it is an epoxy-like material that houses the internal components of the sensor. “If you were to look at our sensor, the first component that you would see in a profile view is a circuit board, a battery and another circuit board that has an antenna on it. That material fills up that sensor all the way up to that transmitting antenna. By doing that we’re going to minimize any potential damage that could result from vibration, impact and the environment.”
The system has a fast-leak warning and a low-pressure warning. If any pressure drops 2.8 psi within 12 seconds, the operator gets a fast-leak warning and they know they are in a critical situation and can react accordingly.
A system that works without anything on the vehicle is Ventech’s Pneuscan, which consists of a sensor on the ground that vehicles drive over to get pressure readings and tread level readings. Krause of Ventech explains, “There is nothing installed on the vehicle, no modification to the vehicle. The sensor plate is embedded into the ground of the transit authority, in a place that’s highly traveled; tire pressure is measured daily or sometimes more than daily.”
“The physical basics are quite easy,” says Pingel. “The pressure that the tire brings to the street is depending on the pressure inside. That means if you have more pressure inside, the surface — the footprint — gets smaller. If you put more load on the tire, than you have a larger footprint.” In other words, the inner pressure transfers down to the outer pressure and what it measures with the sensor is the pressure distribution outside of the tire on the ground and calculates on that, the tire pressures.
Pingel emphasizes, “You can take any vehicle, drive over the sensor and the sensor measures the pressure. We don’t need to know what tire it is, what size of tire it is, the measurement is independent of the tire.”
The primary benefit Krause and Pingel stress is that there doesn’t need to be anything installed on the vehicles or on the tires. And as they point out, if you have 200 vehicles with 10 tires per vehicle, that’s 2,000 sensors, 2,000 connections. “Because there are so many sensors which need to be serviced, it is very expensive,” says Pingel.
Krause summarizes, “I think tire pressure monitoring systems are great, I just like the way that we do it, it is one unit per facility. It’s no moving parts, it’s static, and the information is available to the maintenance supervisor or who ever needs that information.”
Nitrogen-filled systems
Another option many agencies are looking at is nitrogen-filled tires. Lighter of NitroFil shares information from the study, “Tire Nitrogen Filling System,” a final report to Industrial Technologies Sector of Ingersoll Rand Corp. by Nader Jalili, PhD, and Prakash Venkataraman, a graduate student with the department of engineering, Clemson University. According to the study, by inflating truck tires with nitrogen, fuel economy can be increased by roughly 23 percent and tire life increased by 50 percent.
The biggest culprit in the typical air-filled tires is the oxygen. “While oxygen is important for you and I to survive, it’s usually harmful to anything that’s not a living organism,” says Lighter.
Oxygen permeates through a tire approximately three to four times faster than nitrogen because oxygen has a slightly smaller effective molecular size than nitrogen. Nitrogen permeates through the tire more slowly, and it contributes to proper inflation pressure, so improves maintenance for the tire. Better pressure maintenance contributes to reduced tire wear, so tires last longer.
Compressed air with oxygen also contains water. That’s problematic for a tire and for a wheel assembly,” says Lighter. “You want nothing but pressure and that’s what nitrogen provides; no water, no oil, no particulates and, moreover, no oxygen.”
With the technology available and changing at a rapid pace, there are a variety of options available for agencies to save money, improve safety, save fuel and cut greenhouse gases by improving their tire maintenance and procedures. ?
