The sub-cap binds before the group total does
Arkansas publishes two different weight pictures, and the permitted one is not simply the legal one with bigger numbers. 27 CAR § 111-102(c) sets out the legal table the permit rules exist to exceed: 80,000 pounds gross on five or more axles, which must meet the federal bridge formula for 80,000 pounds; a single load-carrying axle at 20,000 pounds; a tandem axle group at 34,000 pounds; a tri-axle group at 50,000 pounds; a single steer or front axle at 12,000 to 20,000 pounds, with the axle required to be rated by the manufacturer for the weight; and a tandem steer or front axle at 24,000 pounds. Width is 8 feet 6 inches and height is 14 feet.
Section 111-306 then sets the permitted axle-group limits, and every one of them carries a second number that does the real work. A tandem group may not exceed 46,000 pounds, and no one axle of that group may exceed 23,000. A tridem may not exceed 60,000 pounds, and no one axle of the group may exceed 20,000. A quadrum may not exceed 68,000 pounds, and no one axle may exceed 17,000. A single load-carrying axle under permit stays at 20,000, as does a single trunnion axle.
Run the arithmetic on the quadrum and the point becomes obvious: four axles at the 17,000-pound sub-cap comes to 68,000 exactly, so the group total is only reachable on a perfectly even distribution. On the tridem, three axles at 20,000 also comes to 60,000. These are not headroom figures with a safety net underneath; they are ceilings that require even loading to reach at all, and an uneven axle in the group takes the whole group out of compliance while the group total still reads legal.
Section 111-305 caps the permitted front steering axle at 20,000 pounds single and 24,000 pounds tandem, citing Arkansas Code § 27-35-203(c)(1) and (c)(2). And § 111-302(8)(C) adds a component requirement that is easy to miss in a definitions section: a load-carrying axle shall have a minimum capacity rating of eighteen thousand pounds. All of these are qualified by an exclusion for vehicles of special design under 27 CAR § 111-401 et seq.
- Permitted single load-carrying axle — 20,000 lb.
- Permitted tandem group — 46,000 lb total, no single axle over 23,000 lb.
- Permitted tridem group — 60,000 lb total, no single axle over 20,000 lb.
- Permitted quadrum group — 68,000 lb total, no single axle over 17,000 lb.
- Permitted single trunnion axle — 20,000 lb.
- Permitted front steering axle — 20,000 lb single, 24,000 lb tandem.
- Load-carrying axle capacity rating — a minimum of 18,000 lb, § 111-302(8)(C).