TraxQStay Legal On The Scales
Check gross weight and axle distribution against federal limits before you scale.
How to use the Axle Weight calculator
Federal limits cap you at 80,000 pounds gross, 20,000 on any single axle and 34,000 per tandem group, and scaling over costs a fine plus being held until it is corrected — the lost time usually exceeding the ticket. There is no federal 12,000-pound steer rule: that number comes off your front axle rating and your steer tire sidewalls, and 23 CFR 658.17(f) only lets a state enforce down as far as the manufacturer's rating. Enter each group from the scale ticket and the output shows which one is over and by how much. The fix is almost always tandem position rather than removing freight: sliding the trailer tandems back moves weight onto the drives and off the trailer axles, roughly 250 pounds per hole on 4-inch spacing and 400 on 6-inch. Worth knowing too that you can be legal on every axle and still violate the bridge formula, which limits weight by axle spacing.
Axle Weight Calculator Questions
The things carriers ask most about this calculation.
What are the federal axle weight limits?
Eighty thousand pounds gross, 20,000 on any single axle including the steer, and 34,000 on each tandem group. The 12,000 figure everyone quotes is not federal — it is the front axle rating on a standard highway tractor, and standard steer tires cap you around 12,350 to 13,220 pounds anyway. States can permit more, but 80,000 is the interstate default and the number most scales enforce.
What is a spread axle and why does it carry more?
Once your trailer axle centres sit more than 96 inches apart they are no longer a tandem under 23 CFR 658.5 — they become two independent single axles at 20,000 pounds each, governed by the bridge formula instead of the 34,000-pound tandem cap. At the classic 10-foot spread that works out to 40,000 pounds on the trailer group, six thousand more than a tandem. Gross is still capped at 80,000, and the 36-foot exception in the bridge formula does not help here because it only applies to two consecutive sets of tandems.
Does an APU get me extra weight?
Up to 550 pounds on the Interstate under 23 U.S.C. 127(a)(12), but only up to the unit's certified weight — a 380-pound APU earns 380, not 550. It lifts your gross, axle, tandem and bridge formula ceilings by that one amount; it is not 550 on each. Carry a written certification of the weight and be ready to show the unit actually runs, because 23 CFR 658.17(n) requires both and a dead APU means you are simply overweight. That regulation still prints 400 pounds because it predates the 2012 increase. Off the Interstate, check the state.
How do I fix an overweight axle?
Slide the tandems. Moving them back shifts weight onto the drive axles and off the trailer axles; moving them forward does the reverse. Each hole is worth roughly 250 pounds on 4-inch spacing or 400 on 6-inch, though the real figure depends on how the load sits — always rescale after sliding.
What is the bridge formula?
A federal rule limiting weight based on how far apart your axles sit — the closer together, the less weight allowed. You can be legal on every individual axle and still violate the bridge formula, which is why tandem position matters as much as total weight.
What happens if I scale overweight?
Fines vary by state and typically scale with how far over you are, from a few hundred dollars to several thousand. You will usually also be held until the load is corrected, which costs more in lost time than the ticket.
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