There are so many factors that affect the fuel mileage of a given vehicle. This includes the driver, the shape and condition of the truck, maintenance, routes, climate, load and of course, tires.
At one point in time, drivers preferred “tall rubber” tires. The idea was that the taller the tire, the fewer revolutions per mile and greater the tire life. Conversely, those kinds of tires came with more weight and higher taxes. Nowadays, many truck tires have low profiles with wide base singles.
The Tread: Lug and Rib Patterns
If all roads were always smooth and dry like NASCAR racetracks, we probably wouldn’t be to concerned with tread patterns, in the real world however, we don’t hault operation whenever it starts to rain. Grooves are put in treads to channel rainwater and snow. Lugs are designed between grooves and the drive tires to give the truck added traction in dirt, mud and snow. All of this is done to maximize the desired attributes of the tire for its selected use, balancing life, traction and fuel economy.
About 1/3rd of fuel consumed by a typical truck goes to overcoming rolling resistance in tires. The tread is responsible for 50-70% of that. A switch from lug to rib treads can result in fuel use savings of 2-4%. Aerodynamics also play a role in fuel savings once the truck exceeds 50 mph. When operating at below 50 mph, rib treads can have a huge impact – increasing the savings to 6% for trucks traveling in lower speed urban operations.
As long as tires wear evenly, it’s actually better to keep them on the truck as they wear down. The thinner tread flexes less and flexing creates friction which is the main contributing factor of rolling resistance. A tire worn to 50% of tread depth is 4.5% more fuel efficient than a new tire.
Underinflated tires can reduce fuel economy. In a study done by TMC and FMCSA in 2002, only 44% of about 90,000 tires actually gauged were found to be within 5 psi of their target pressure, and manual tire monitoring practices have not changed much since then. What has gotten better is the increased use of tire pressure maintenance systems. Companies are coming out with innovative tools and systems that allow truck owners to make sure their tires are inflated properly.
Tire systems are designed to do specific jobs. All require sufficient inflation pressure to perform well, just as all require highly engineered components – tread designs, rubber compounds, structures and configurations designed to work together achieve their goal.