Modern trucking fleets face difficult challenges on a day-to-day basis. Fuel efficiency is one of the most important concerns to the contemporary fleet owner.
Volatile oil prices dramatically affect the cost of fleet operations and maintenance. Growing environmental concerns push the development of green technologies and shape consumer perceptions of businesses. New government regulations to decrease greenhouse gas emissions force companies to comply with new methods of operation and expensive equipment upgrades.
Every one of these issues affects the most important of any business owner’s concerns: the bottom line.
Fuel costs are one of the primary financial burdens for any trucking company. Recently, fluctuations in fuel prices have been unpredictable, rapid and drastic. Over the past few years, the short-term price of diesel exceeded $4 per gallon for a significant period of time.
Average diesel prices continue on a steep upward slope that surpasses inflation rates. There is a significant level of uncertainty regarding the price of fuel in both the near- and long-term futures. Trucking companies are constantly looking for ways to increase fleet fuel efficiency: improved engine efficiency, improvements in truck aerodynamics and advances in tire technology are among them.
Improved fuel efficiency ensures a healthier bottom line and cushions companies from unexpected or erratic price increases.
Green business practices reap rewards for trucking companies. In the current political and global climate, a great number of consumers and clients expect environmentally responsible actions from suppliers and business partners. When choosing goods and services, many customers give their business to companies doing more to protect the environment.
To confirm a positive environmental commitment to their customers, trucking companies may participate in the SmartWay program coordinated by the EPA. SmartWay provides promotional tools to green companies meeting their standards. Tractors and trailers from eight major manufacturers are SmartWay certified by the EPA, as well as tires and other individual components for these trucks.
Trucking companies that are active SmartWay partners may display the SmartWay mark on their tractors and trailers, which symbolizes that fleet’s efforts to save energy and protect the environment. Voluntary green business practices like SmartWay demonstrate genuine character and concern for everyone involved.
Government regulations continually increase requirements to reduce greenhouse gas emissions. California-based trucking companies must abide by some of the most stringent regulations in the U.S. Recently, the California Air Resources Board enacted a new regulation targeting heavy-duty tractors pulling 53-foot or longer box-type trailers. Companies subject to this regulation must use EPA SmartWay-certified tractors and trailers, or retrofit existing tractors and trailers with SmartWay-verified technologies.
These SmartWay-verified technologies include improvements in aerodynamics and the use of low rolling resistance tires. California leads the way in regards to new environmental regulations, and there is a strong probability of other states following suit with similar requirements.
Rolling Resistance
Tire manufacturers are aware of these requirements, and the obstacles and concerns of trucking companies when it comes to improving fuel efficiency. Engineers are constantly developing new technologies and design strategies to address the need for lower rolling resistance tires while retaining other important performance characteristics.
Wide-base tires, specialized compounds and improved manufacturing processes are successfully decreasing the rolling resistance of specific tire makes and models. Also, tire companies are actively working to improve maintenance awareness to their customers through seminars, Web resources and product literature.
At the same time, proper maintenance and inflation remains one of the most overlooked ways to substantially increase fuel efficiency and tire life.
Low rolling resistance tires clearly deliver a significant improvement in fuel mileage. A 3% reduction in rolling resistance translates to approximately 1% in fuel savings. Trucks fitted with low rolling resistance tires may see anywhere from a 1% to 10% and upwards savings in fuel, dependent on the tires that were replaced. This means that different tires may have a rolling resistance performance varying by 30% or more.
Two main types of low rolling resistance tires are available today: Standard size tires specifically designed for decreased rolling resistance and super wide designs, which replace standard dual drive and trailer wheel configurations.
Engineers designing standard tires specifically for lower rolling resistance implement a number of techniques. Improvements in tread rubber compound properties, advancement in manufacturing processes, finite element analysis tools for development, weight reduction and decreased non-skid depth are the most prevalent methods used for improving rolling resistance.
The tire tread accounts for a substantial portion of a tire’s mass and typically contributes 35% to 50% of a tire’s rolling resistance. Not only does tread rubber account for a generous portion of a tire’s fuel economy, it also greatly influences tread wear and traction.
The use of low rolling resistance tread compounds can significantly improve the fuel efficiency performance of a tire. However, the creation of low rolling resistance compounds can result in possible tradeoffs, such as decreases in traction and wear performance. The trick is to develop the compound such that rolling resistance is improved while retaining these other important performance properties. That means that all of the key characteristics must be addressed at the same time, not independently of each other.
Manufacturing for Efficiency
Tire manufacturing processes, particularly curing, can be altered to affect certain tire characteristics, including rolling resistance. The two main manufacturing processes are the assembly of the “green” tire and the curing process. During green tire assembly, components are wrapped in a particular order around a metal cylinder, forming the composite uncured, or “green,” tire. This green tire is then inserted into the mold and heated to a high temperature for a certain amount of time, determining the final shape and look (tread pattern and sidewall) of the tire. Curing also helps determine the precise performance of the tread and sidewall compounds.
The most significant variables during the curing process are total time in the mold, and the temperature at which the tire is cured at any given time. Varying these parameters can significantly affect the performance properties of the tire, including rolling resistance. Curing process optimization in conjunction with improved materials and tire design leads to tires with lower rolling resistance.
Advanced finite element modeling aids engineers in making more accurate predictions as to how changes in tire construction will benefit rolling resistance performance. Computer simulation enables the engineer to make changes in cavity shape, component geometry, compounds and other parameters so that they can predict performance parameters through a variety of service conditions. This also helps decrease development time, improve the final product and reduce costs.
Potential tire designs – design candidates – are compared using this information, leading to a tire model that is optimally designed for rolling resistance and other key performance characteristics.
Super wide tire designs, specifically the 445/50R22.5 designed to replace duals on drive and trailer axles, currently offer the most significant improvement in tire fuel efficiency.
These tires offer superior low rolling resistance and a significant weight reduction when compared to the standard dual configuration. Even when compared to dual tire configurations of already low rolling resistance tire models, the super wide designs are significantly better.
Not only can the weight reduction improve a truck’s load capacity (higher revenue), trucks having trailer and drive positions fitted with super wide tires can experience a 1% to 10% improvement in fuel economy (reduced costs), dependent on the tire models replaced.
Looking Ahead
Tire manufacturers also participate in the EPA’s SmartWay program. Trucking companies looking for the lowest rolling resistance tires can find information on these products quickly at the SmartWay Web site. Only tires meeting SmartWay’s stringent rolling resistance criteria are approved, and both standard and super wide tires can be SmartWay verified.
New tire designs and improvements in compounds and manufacturing processes are continually producing even more fuel-efficient, lower rolling resistance tires. Through these new products and technologies, tire manufacturers provide trucking companies with several options to improve fuel efficiency.
In the foreseeable future, fleets will have even greater fuel savings requirements in order to operate more efficiently, environmentally friendly and economically. As a result, tire company engineers will continue to face new development challenges and will surely create new compounds, designs and processes to meet ever-increasing demands.
Clinton Covey is a TBR Development Engineer for Hankook Tire America
