Load Weight Distribution

Federal weight rules under 23 U.S.C. § 127 apply separately to each axle group -- steer, drive, and trailer -- in addition to the overall gross vehicle weight. A load can total well under 80,000 lbs and still violate an individual axle group's statutory limit (34,000 lbs for a tandem group) if the cargo's weight distribution puts too much of it over one particular axle group, which is exactly why this calculator checks all four limits -- steer, drive, trailer, and gross -- independently rather than only the total.

Gross Weight is simply Tractor Weight plus Trailer Weight plus Cargo Weight -- a straight sum that doesn't care where the cargo sits or how the trailer is configured. Cargo Position, Trailer Length, Kingpin-to-Rear-Axle distance, and Total Axles only affect how that same total weight is estimated to distribute across the steer, drive, and trailer axle groups -- not the grand total itself.

Not exactly. The federal single-axle statutory maximum is actually 20,000 lbs, but roughly 12,000 lbs is a widely used practical steer-axle target in the trucking industry, driven mainly by typical steer-tire load ratings rather than a single nationwide steer-specific statute. Some states also impose their own steer-axle limits, so always check the specific limits that apply to your route rather than treating this figure as a universal legal ceiling.

No. This calculator checks each axle group against a flat weight limit (for example, 34,000 lbs for a tandem group) rather than computing the Federal Bridge Formula's spacing-dependent allowable weight, which can require a LOWER weight than the flat group limit when axles are spaced closely together. Total Axles is collected as an input but does not currently change any calculated weight or limit, so for a full legal compliance check you should also verify your specific axle spacing against the Federal Bridge Formula.

The kingpin sits somewhere back from the trailer's front wall, not right at it, so this calculator estimates that offset as Trailer Length minus Kingpin-to-Rear-Axle -- assuming the rear axle group sits at the very back of the trailer -- and subtracts it from the cargo's front-referenced position before dividing by Kingpin-to-Rear-Axle in the lever-arm formula. That keeps the input you enter (position from the front, which is what's usually visible when loading) consistent with the kingpin-anchored physics the axle-weight split actually depends on.