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As an alignment expert and owner of LaserLine, Inc, I’ve gotten used to being asked a lot of questions about truck alignment. Two of the most pressing questions I’m asked are what affects fuel mileage and how can we, with alignment, diminish or lessen those forces that rob us of fuel efficiency?

Let’s start where we should, at the beginning, which, fittingly, is the front of the truck. Barring any suspension damage, the only thing on the front of the truck, or the bobtail, which I will subsequently refer to as “the power unit,” that can affect the fuel mileage would be the toe setting. Toe can be imagined as a set of skis- let’s say your steer tires are skis.

Too much toe indicates “positive toe” and would look like the ski tips are facing toward each other, affectionately known as a snow plow maneuver. “Negative toe” or toed out would be just the opposite, with the points of the skis facing away from one another, causing the skier to plant his face in the snow. Not a pretty visual, especially if that skier weighs around 16,000 pounds (an even worse visual).

Proper toe setting is crucial. But surely there is more, you say! And there is. The front end is where many alignment shops would stop, but this is not the real villain in our battle for fuel mileage. The real problem lies not in front of us but behind, so let’s skip to the end, which would be the trailer.

Trailers have “dead axles.” A dead axle is one that is not powered and does not steer. It must be drug along, like the dog in National Lampoon’s Vacation… Each of these dead axles has four tires (or, in the case of “super singles,” two really wide tires). Now, if these axles are steering off the road to the right, the truck must not only pull the trailer forward down the road, but must also constantly pull the trailer back up to the left, onto the road. If the axles steer one to the left and one to the right, now we have the same forces as would our steer axles in the snow plow position, one trying to go one way and one trying to go the other.

So, now while you are trying to understand the effect the misaligned trailer axles have on our fragile cost per mile ratio, let’s go ahead and throw in around 30 tons of weight. Suddenly, a minor misalignment of the trailer axles becomes a 30+ ton anchor being drug down the road, robbing us of fuel mileage and driveability.

When we align trailers, the trailer axles are set to hold the trailer on the road, taking the crown (or slope) of the asphalt into account, so the power unit does not have to pull it up or down the roadway surface. Using the laser equipment that we have, the trailer axles are not even parallel, but instead both axles are aimed independently at a single point directly centered on the body of the trailer, giving us the optimum tracking for all four trailer axles. Now all that the power unit has to supply is the forward motion without fighting the forces of gravity or the axle thrust scrubbing one against the other. So now it’s like walking a well-behaved heeler instead of trying to pull a rhinoceros backward through a Chinese finger trap. Didn’t see that one coming, did you?

So, in closing, I hope I have answered some of the fuel mileage questions in regard to alignment. I’ve undoubtedly created several more. The real message that I would like to get out there would be simply this: The light at the end of the tunnel can be found in the rearview mirror- the less the power unit has to work to pull the trailer straight down the road, the better the fuel mileage.
How an Alignment Affects Fuel Mileage
posted by Kraig (LaserLine, Inc, eastern Idaho)