A variety of factors can influence the productivity and longevity of the dump trailers in your fleet. To ensure they deliver the performance and service life you expect, it’s important to determine the appropriate setup for the application, and then operate and maintain the trailers for both optimum efficiency and longevity.
Long and short of it
While dump trailers and tractors offer advantages over a conventional dump truck in many applications, properly setting up a tractor/trailer combination is more important than you may realize. Whether you run end dumps, side dumps or bottom dumps, matching the truck to the trailer influences productivity.
“Matching a truck to a trailer is really something that deserves more attention than it is often given,” says Charlie Wells, East Mfg.
Many contractors own a variety of trailers, ranging from lowboys to dumps, and try to pull them with the same trucks. But this is changing. “It is a growing trend that people marry trucks and trailers together because of the overall efficiency gains,” says Jim Ladner, national sales manager, Landoll.
Consider a 39-ft. dump trailer. To maximize the load in many parts of the U.S., you need to follow the Federal Bridge Formula. “To get your Federal Bridge, you need 51 ft. from the front axle to the rear axle,” says Ladner. “That is the outer bridge. The inner bridge is the front drive axle to the rear axle of the trailer. That has to be 36 ft. With those two lengths, you can gross 80,000 lbs.”
The closer to these measurements, the better. “It doesn’t help if you are 1, 2 or 3 ft. longer,” Ladner states. If you use a sleeper cab, you may be 5 or 6 ft. longer. “You take away from payload and pull that extra weight down the road all day long. If you can operate within the Federal Bridge with a truck that has a 190-in. wheelbase, why operate a 250-in. wheelbase? You lose maneuverability. You are losing payload and increasing cost of ownership.”
Most construction operations want short trailers. “You have to keep short for maneuverability in the yard,” Wells states. “That is when you find that a shorter multi-axle dump trailer is better.”
Longer 39- or 40-ft. dump trailers are typically configured as five-axle rigs — three on the tractor and two on the trailer. But when you move toward shorter trailers, you need multiple axles to meet federal and local weight regulations. The length of the trailer influences the best tractor configuration.
“A general rule of thumb is a short wheelbase tractor, defined as a 185 in. or less wheelbase, is optimum with a short multi-axle (three or more axle) dump trailer,” Wells states. “So you want a long wheelbase with a long tandem dump trailer and a short wheelbase with a shorter, multi-axle dump trailer.”
But there are setup considerations with multi-axle trailers. “The fifth-wheel height becomes an issue because the closer the trailer can run to level, the easier it is to set ride height on suspensions and get the axles to equalize,” says Wells.
A challenge with longer five-axle rigs is getting weight transferred to the steering axle. “Any time you can spec heavy components on a truck as far forward or a set-back axle, that is more optimal,” says Wells. That means less weight has to be transferred to the steering axle.
Shorter tractors can really help with weight transfer. The shorter the truck you use, the closer that front axle is to the load. “A set-back axle naturally moves that axle closer, so it is a good choice,” says Ladner. “You always want to take maneuverability into consideration. You are always trying to get into and out of places and the shorter tractors and shorter trailers just give you enhanced maneuverability that allows you to go places that you can’t take longer vehicles.”