Hauling a trailer behind a vehicle allows great freedom to move cargo around to different locations. But a trailer's axle must be precisely aligned so the load is balanced and safe on public roadways.
A trailer's axle spans the width of the trailer's underbelly, carrying two wheels on either side. If alignment procedures are incorrect, the load on the trailer can veer forward or backward, resulting in strain on the towing vehicle's engine and sway within the trailer's driving lane.
For a trailer axle to be properly aligned, 60 percent of the trailer's foremost portion should be in front of the axle's center point. This results in 40 percent of the trailer's tail end remaining behind the axle's center point. For example, if a trailer is 10 feet long, 4 feet of the trailer is behind the axle, and 6 feet is in front of the axle.
Keep in mind that this alignment procedure does not include the trailer's tongue, or triangular attachment point, into the calculation. For the correct alignment, all measurements are done within the rectangular body of the trailer only.