Super Dumpers boost truck payload to 25 tons

Aug. 1, 2003
Truck body and lift axle suppliers are combining forces to equip straight trucks to haul a legal payload of more than 25 tons. The new Super Dumpers on

Truck body and lift axle suppliers are combining forces to equip straight trucks to haul a legal payload of more than 25 tons. The new Super Dumpers on seven axles are legal at 80,000-lb GVW in eight states — Arizona, Nevada, Utah, Washington, Oregon, Missouri, Minnesota, and Ohio.

To get 80,000-lb gross, the truck must have seven axles in a 36-ft wheelbase and within 40 feet overall length. This requires three pusher axles and one booster axle to the rear. The booster axle helps shift more weight to the steer axle operating at 18,000-lb GAW. With 34,000 lb on the drive tandem and 12,000 lb on the booster axle, the three pusher axles combined must carry 16,000 lb.

This is no one-of-a-kind experimental truck. The Mack booth at the International Trucking Show in Las Vegas showed a seven-axle truck that is one of an order for 10 identical units. The buyer has a fleet of 46 six- and seven-axle trucks operating in Mesa, Arizona. Fiesta Trucking Company hauls hot rubberized asphalt loaded at 300°F, as well as aggregate.

Fiesta President Ray Bossey says the seven-axle Supers can dump right into the paving hopper without interference from the booster axle. He says his company has a policy of not overloading and will not overload. He says his rigs weigh out legal on every axle. His six-axle Super Dumps with a booster axle and only two pusher axles operate at a GVW of 75,500 lb. His seven-axle rigs operate at 80,000-lb gross and net 51,000 lb or more payload.

The Fiesta trucks start with a heavy-duty, lightweight chassis, the Mack Granite Bridge Formula truck that originally was developed as a concrete mixer chassis. With a 108" BBC and 29" front axle spacing, it is ideal for booster axle applications. The truck wheelbase is 258".

Fiesta spec'd the Macks with a pedigreed Bulldog drivetrain — Mack 427 ASET IEGR engine, Mack 300 series triple countershaft transmission, and Mack steer and drive axles. The tandem suspension is a Hendrickson HN462 suspension rated at 46,000 lb.

The elliptical body by Reliance Trailer Manufacturing in Cotati, California, has a 4-millimeter floor of SB 50 steel from Sweden. The 17½-ft body has 60" sides of 10-gauge Cor Ten steel because of a corrosive release agent used with loads of hot asphalt.

The body has such niceties as 14-gauge stainless steel fenders bolted on for easy replacement. The fleet sometimes hauls aggregate that would chip painted fenders. An aluminum tailgate saves 160 lb of weight. The electric Aero tarp is controlled from the cab.

Two hydraulic pumps and PTOs are mounted, one for the dump body and one for the booster axle. This is a safety measure because the pump for the Maxle booster axle runs almost continuously when loaded. A 35-gallon rectangular hydraulic reservoir fabricated in the Reliance plant is mounted back of cab.

The Maxle booster axle by Silent Drive has a full 80" track axle for greater stability and safety. Hydraulic arms put the axle on the ground, and then the Silent Drive air suspension takes over to adjust to road conditions. The rear corner posts of the Reliance dump body are designed 12" forward and slanted forward to accommodate the Maxle arms in the raised position.

The three underbody lift axles are the new 8,000-lb capacity, lightweight steerable axles from Watson & Chalin. While they must carry only 16,000 lb together, placement is critical for proper weight distribution, axle grouping, and truck handling.

These are premium trucks equipped with premium accessories. Owner Ray Bossey estimates their cost at about $175,000. Past experience proves they are money makers.

About the Author

Paul Schenck | Senior Editor