With the price of oil dominating the headlines, fleets are looking for every possible way to squeeze a few more feet out of every gallon of fuel. As a result, more attention is being paid to the ever-growing number of new and retreaded truck tires that feature low rolling resistance compounds. Rubber has come a long way since sulfur and a hot stove, but coincidently, oil has made the most significant impact on the tire industry. Synthetic and natural rubber blends are now engineered for specific applications, and the end result is a variety of so-called “boutique” rubber compounds that are customized for fuel efficiency.
Reducing the amount of drag created by truck tires can be accomplished in a number of ways. One of the most common methods is to convert vehicles from standard profile tires to low-profile. The theory is that a smaller and lighter tire requires less horsepower and reduces the amount of air resistance because it occupies a smaller space. In reality, however, changing drive axle tires to low-profile sizes can actually have a negative effect on the gearing and cause the engine to operate at a less-than-ideal range.
Another approach to reducing the amount of rolling resistance attributed to tires is to switch from deep to shallow tread. Studies have shown that fuel consumption improves by as much as 6% after a standard tire is 50% worn. Of course, switching to shallow tread depths means tires won't last as long, so better fuel mileage might come at the expense of a higher tire cpm.
The latest movement to reduce rolling resistance centers on replacing dual tires with ultra-low profile wide-base singles. In many instances, these tires are showing an immediate improvement in fuel economy, not to mention a better ride for the driver. The single assembly also weighs less than their dual counterparts so the vehicle load can be increased. But they are not readily available, especially in more rural areas, and require the purchase of special wheels. These tires are also relatively new to North America, so long term retreadability is still being determined.
Fleets should not expect substantial returns at the fuel island when switching to tires and retreads with low rolling resistance compounds or features. Nor should they expect low profile or ultra-low profile wide-base singles to have a significant impact on miles-per-gallon. There are definitely advantages to these approaches, but studies have shown that vehicle speed, load and air resistance have a much greater impact on fuel consumption.
However, if the advantages of low rolling resistance tires and retreads do not come at the expense of performance or cost-per-mile, then the fleet has nothing to lose. When all tire-related operating expenses remain equal, even a 1% gain in fuel mileage will add up over the course of a year. It's going to require extensive testing and diligent recordkeeping to truly determine if there are any advantages, but the payoff can be realized in the right applications.
Finally, there is one thing that every fleet can do to reduce rolling resistance attributed to tires. By regularly checking and maintaining the inflation pressure, miles-per-gallon and cost-per-mile will be maximized, regardless of the tire or retread construction. Even the most advanced low rolling resistance rubber compound in the universe cannot overcome the effects of under-inflation or overloading, so fleets expecting a return on this new technology must understand that it starts with an air gauge.