They’re called 18-wheelers, and every one of those 18 wheels has a tire on it that offers you the opportunity to save some money if you make the correct choice when you purchase it.
Whether it’s standing still or rolling down the highway, a tire has a somewhat oval shaped footprint because it flexes and deforms as its round shape meets the flat road surface. This flexing causes heat to be generated within the body of the tire—mechanical energy is changed into heat energy, which is lost for all time. While there are other energy losses due to a tire’s rolling resistance, the generation of heat is the most significant. All else being equal, the less flexing a tire undergoes as it rolls down the road, the lower its rolling resistance and thus the more energy-efficient the tire will be.
In an effort to establish a program to verify low rolling resistance tires, SmartWay reached out to several major suppliers of Class 8 tires to the OE market to gather rolling data of each manufacturer’s best-selling tire for each axle position. For each tire model, SmartWay had test data provided by at least two different sources using a widely-accepted SAE tire rolling resistance test method to establish baseline values for typical new Class 8 tractor-trailer line haul OE tires.
Using these results, along with discussions with tire experts and computerized simulations, SmartWay estimated that reducing tire rolling resistance by approximately 15% could reduce fuel use by about 3% for a typically loaded Class 8 tractor-trailer line haul truck.
To achieve 3% fuel savings, SmartWay then defined tire rolling resistance targets that were 15% lower than the baseline values for such typical tires. For several years after the launch of the tire verification program, SmartWay allowed manufacturers to demonstrate that they met the targets using several different methods, including averaging tire rolling resistance values across a complete set of tires—steer, drive and trailer—to meet the total vehicle rolling resistance target.
SmartWay also allowed manufacturers to test tires on a vehicle in a track test. Candidate tires needed to result in a 3% or greater fuel savings compared to a vehicle equipped with typical tires.
Earlier this year, SmartWay eliminated both of these verification options. Although they provided flexibility for tire manufacturers, in practice, there is no good way to know whether tires that are verified as a set are used together. Another change in the works this year is to transition the verification test method from SAE test procedures to a new ISO tire rolling resistance test method. This change is primarily intended to eliminate differences in test results due to differences among test labs.
Since a major goal is to accelerate market penetration of the best available technologies, SmartWay intends to lower all its rolling resistance targets over time. These changes would encourage all tire manufacturers to catch up to today’s lowest rolling resistance tires, providing even more fuel savings for trucking fleets that rely upon SmartWay verification for their tire choices. SmartWay is also exploring options to verify retread tires.
Although not all applications have SmartWay tires as options, most do. And taking the option truly is the smart way to go.
