A Tire in Your Tank

The right tires can improve fuel efficiency, if you follow some simple guidelines.

Every day, you and I see successful fleets operating on our nation's roadways. But do you ever consider the financial constraints these fleets must face in what appears to be an environment that is ripe for the trucking industry? If you're in the norm, I'm sure that you are unhappy about the rising cost of fuel, and the overall effect it has had on your pocketbook. The reality is that those successful fleets feel the same pinch that you and I feel.

Every fleet I know has added a fuel surcharge onto the costs of transporting goods. But the really progressive fleets, no matter what their size, also seek ways to improve the fuel efficiency of their equipment. They do this as opposed to simply transferring all the additional fuel costs onto their customer base. It's one of the many arrows in their quiver, helping fleets remain competitive in today's market.

Chasing fuel efficiency can go in several directions. Aerodynamics, gearing, engine choice, ride height, speed limiting, idling substitutes, and alignment practices all effect fuel consumption. However, as a tire engineer, let's discuss my favorite, "Choosing the right tires for fuel savings." Fuel efficient tires are most effective in line haul operations. Placing fuel efficient tires in other applications may seem like a good idea but cut/chip resistant compounds are not conducive to fuel efficiency. So what is it about a tire that makes it fuel efficient?

Often people will tout the praises of rolling resistance, (the drag force required to put a free rolling tire into motion, but by itself rolling resistance does not answer all the questions. Manufacturers use advances in rubber compounding, primarily the tread cap compound, as well as reinforcement materials in the casing that lend themselves to improved rolling resistance. Usually, the consequence of using these compounds and reinforcements is that other areas of performance are affected. The key is to use a cost per mile model that takes into account total tire life including repairs, and any payload increases that may result from the fuel efficient tire changeover.

Any time consideration is given to the rolling resistance of a tire, you must also consider the tread depth of the tire when new. A new fuel efficient drive tire at 26/32nds will have to save a significant amount of fuel to offset the mileage loss when compared to the same sized standard drive tire at 30/32nds. So when looking for a tire that is fuel efficient, look for the correct compound combined with the deepest tread possible. The best way to judge a compound is to look at the manufacturer's SAE certified measurements, because it is a standardized test.

When planning a change to fuel efficient tires, it is necessary to look at which wheel positions will affect fuel consumption the most. While manufacturers differ slightly on the exact percentages, the approximate contribution by wheel position to the total possible fuel savings is 13 percent for the steer position, 48 percent for the drive position, and 39 percent for the trailer position. If, in your quest for the best fuel efficiency, you change out the tires on the tractors only, leaving the trailers alone, you are ignoring 39 percent of the total fuel contribution. The best scenario would be to change out all wheel positions when considering fuel savings, but if one position must be sacrificed, that position should be the steer tires.

You can also incorporate fuel efficient technology into retreading. If you put all of the effort necessary into purchasing fuel efficient tires, it is important that you capitalize on your investment in the casing and utilize a retread with a fuel efficient compound. It is safe to assume that a fuel efficient premium tire is built with a fuel efficient casing, so utilizing the proper retread can help to maintain or enhance the savings of your original fuel efficient tire. If you specify a tread cap that is not designed with fuel efficiency in mind, you could lose potential savings. Additional guidelines for retreading with a fuel efficient tread are to make sure that you maintain your casings, and specify that no outside casings be used for your retreads. Capping any casing with a fuel efficient tread cap does not necessarily guarantee a fuel efficient retreaded tire. The casing itself should be targeted with fuel efficiency in mind.

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