Bottom Line
Maximum Cube

by Paul Abelson, 
senior technical editor

More than 70 percent of you pull van trailers. Of that number, many of you gross out on every load. If so, maximizing cubic space really isn’t an issue. Many of you have dedicated runs, so your trailer stays pretty much the same from load to load.

Then there are those of you whose loads vary from trip to trip. Sometimes you’ll want to load to 80,000 pounds, only to find that on the next run, you run out of volume at 66,000.

For those of you who need maximum flexibility in your operations, the question is, “How can I maximize interior cargo volume?” Another way to ask the question is, “What can I do to provide the greatest flexibility to meet my customers’ varying needs?”

To find out, I called OOIDA member Mike Swiger. When he pulled for Roberts Express/FedEx Custom Critical, he never knew what kind of load he’d have from trip to trip. He shared some experiences, then recommended I contact Ted and Elvin Spellman at Spellman Trailers, Franklin, WI. They’re on Ryan Road, a few miles west of I-94, just south of Milwaukee. I visited for a few hours with Elvin at this family-owned and -operated dealership.

My observations confirmed Mike’s recommendation. They know their stuff, and they treat their customers well. What follows is based on both Mike’s and Elvin’s comments and suggestions.

First, make sure your trailer interior is equipped with some kind of track to provide versatility in securing loads. Far too many trailers have plain plywood-lined trailers. They rely on load bars and hoop sets for adjustable cargo securement. These work, but there are better, more secure and structurally sound alternatives. The answer is using track to provide attachment points for a wide variety of cargo control systems, from straps to bars to beams.

While declining in popularity over the past few years, horizontal E track is a good choice if you plan to provide decking at a constant-height or if you want more flexibility in the horizontal direction than in the vertical.

By the way, the letter designations for track, “A,” “E” and “F” indicate the shape of the opening and the dimensions of the holes into which various cargo control devices fit. A and E have rectangular slots 2.42 inches high. F track has 0.75-inch diameter round slots. Horizontal E and A track have slots 2 inches apart. Vertical track, also called logistical posts or logi-posts, has the slots 4 inches apart. F track holes are 1.63 inches apart.

A and E track are found along trailer walls, while F track is used mostly flush mounted in floors to anchor vertical shoring.

Vertical A or E track, usually 24 inches apart, offers the greatest amount of flexibility in loading. The specially designed support beams adjust for trailer width. Typically, beams for 96-inch trailers adjust from 85 inches to 94.7 inches, and for 102-inch trailers, adjustment is from 92.3 inches to 102 inches. If you expect to have heavier loads to brace or deck, you can mount logi-posts on 16-inch or even 12-inch centers.

Either horizontal track or logi-posts allow the use of bars for decking lighter or bulkier loads. Floor to roof vertical track also adds to the structural rigidity of the trailer, although in order to save weight, some operators install shorter lengths from the upper sill to about halfway to the floor. The half posts do not affect trailer structure.

Standard beams can each hold 2,000 pounds uniformly distributed; heavy-duty beams, up to 3,000 pounds. With bars spaced every two feet, you can load a second tier with as much as or more than you can on the floor, but it’s always a good idea to keep your loads, and the trailer’s center of gravity, as low as possible. Pallet loads can sit right on the beams, but floor loads and boxes or drums may need their own deck. One-half- to 3/4-inch plywood in 4-foot by 8-foot sheets should provide adequate flooring.

Where are you going to store all your load bars, beams, plywood sheets and strapping you use to make sure everything is secure? There are several options. You can place horizontal track 12 inches from the trailer roof, running back about 10 feet back from the nose. If you have vertical track, use the slots 12 inches from the top. With a few beams and some plywood sheets, you can have a convenient shelf up top, in an area that won’t interfere with loads on the floor.

Your trailer dealer can also install exterior storage. That can be anything from pallet racks fabricated from angle iron or aluminum extrusions for weight, to factory-built tool and utility boxes mounted under the trailer. Some drivers use full-width boxes running from behind the landing gear to just in front of the tandems. Boxes can also be hung on the tractor chassis. Some drivers decorate their tractors with headache racks, with or without locking cabinets. The racks have provision to secure load bars and beams, while boxes and cabinets allow external storage of everything from furniture pads to carpenters’ tools, air tools to dunnage.

If you’re buying a new trailer and maximum cube is the main consideration, look at a drop-frame trailer. This construction adds cube, but there are other considerations that should enter your decision process, such as wheel and tire sizes and brakes. To make room for the lower floor, some drop frame trailers run on 19.5-inch wheels and tires. These tires turn more revolutions per mile, stressing seals and bearings. The 265/70R19.5 have less load-bearing capacity than taller, wider rubber. The smaller wheels reduce airflow around brakes, leading to increased brake wear. But the added cube may be worth having. Like most things in trucking, trade-offs must be made.

If you plan to expand your business opportunities with temperature-controlled loads using low-level refrigeration, you’ll want the smallest reefer unit that will meet your needs. There’s a vast difference between keeping sensitive cargo cool and carrying ice cream or frozen foods. You might be able to cool or heat adequately with a smaller unit with less intrusion, requiring less nose space. You also can use thinner insulation on the sidewalls. For each half-inch you reduce insulation on each side of a 48-foot trailer, you increase the interior more than 36 cubic feet.

When it comes to maximizing cube, remember, you can’t be all things to all customers. The law of diminishing returns states that it gets increasingly expensive, in cost or resources, as you approach the maximum. In practical terms, it may cost way too much to equip your rig to satisfy conditions you may encounter only 2 percent or 3 percent of the time. Unless the revenue from those few customers is high enough to cover the costs and extra weight you’ll carry while serving the other 97 percent or 98 percent of your customers, don’t try to satisfy every possible situation.

If you’re going to make money, you have two choices. Target the 95 percent of your market that is easy to service and learn to walk away from difficult customers, or specialize in the difficult as your niche market. If you can serve the most demanding 5 percent, you can earn the top 5 percent of rates. You’ll need to get lots of money, because the cost of satisfying these customers can be quite high.

Once again, thanks to Mike Swiger for sharing his experiences, and to Elvin Spellman for taking time from his busy shop to show how everything comes together.

Paul Abelson can be reached at