Economy & Scales

Order a long conventional with a monster sleeper and a big motor and you’ll easily wind up with a tractor weighing 22,000 pounds. Go to the other extreme and you could be at 14,000 pounds. The heavier machine is going to be sexier, but that 8000-pound difference could well become paying freight.

Even the idea that a lighter truck lacks that heavy-truck “feel” is being challenged. In March, Western Star rolled out a 14.000-pound 4964FXL tractor with a 62-inch Star Light sleeper. It’s a standard Constellation Series truck with dual exhausts, dual air cleaners, dual 100-gallon fuel tanks, a Cummins ISM engine, an aluminum rear-axle carrier, a 1300-square-inch crossflow cooling module, and a very lightweight wheel and tire package.

If you can live with a single drive axle and a day cab, you can even get down to the 12,000-pound range. In June, Mack Trucks previewed a new Ultra-Light Vision day cab tractor that weighs just 12,246 pounds. The company calls it a “concept vehicle,” but it may well hit production. The tractor uses super-single tires and aluminum all over -from the battery-box cover to the flywheel housing.

You can go too far in a quest for lighter weight, so bear in mind your application. Some lightweight components aren’t as robust as their heavier counterparts, and they’ll likely cost more as well. So ask yourself how quickly you could recover that money, remembering that a light truck uses less fuel. And obviously a bigger payload is more than just a bonus-especially if you’re an owner-operator paid on a percentage-of-revenue basis.

So how do you get the weight out? Some tractors are inherently lighter because the cab is aluminum, but mostly it’s a pound-by-pound process, 50 here and 95 there. The easiest way is to spec aluminum components where you can, but there are many new products being introduced that shave serious weight simply by better design.

THE BASIC SPEC

A long wheelbase with a condo out back looks good, but it’s obviously going to be heavy, so you have to ask if a smaller truck might be in order. If you or your drivers don’t live in the truck for days on end, maybe a basic 42-inch bunk is a better choice than the 500-pound heavier 60-incher, for example.

And do you need all those aerodynamic roof fairings if you’re pulling flatbeds or dumps? They’re relatively lightweight plastic, but they’ll actually hurt fuel economy if your load/trailer height isn’t right up there at the max. A full-tilt fairing package amounts to as much as 900 or 1000 pounds, so make sure you need it.

THE ENGINE

Some of the latest big-bore engines are remarkably lighter than their earlier counterparts. The big Cummins Signature 600, for instance, weighs about 2650 pounds compared to 2805 for the N14 by means of better design in general and features like an integrated engine brake. But look at the 10.8-litre ISM at just 2070 pounds. Cat’s C12 is about the same, and that compares pretty favorably with some 2700 for a C16. Detroit’s 12.7-litre Series 60 is in the 2600-pound range, while Mack’s E7 and Volvo’s VED12 are about 2300.

Can you live with a 10- or 12-litre engine as opposed to 14 or 15 litres? There could be lower resale value, and if you use a smaller diesel in an application that cries for 14 litres, there may be durability issues.

Performance-wise, however, these days you can find 10 to 12 litres that produce serious power and respectable torque. Spec’d right-meaning well matched to the application-a smaller diesel won’t necessarily make you suffer in either longevity or performance terms.

Whether you go for a smaller-capacity engine or a big engine with a lower horsepower rating, like a 435 instead of a 500, you’ll be able to spec a lighter transmission, driveline, and rear axle set. Chalk up 200 pounds or more.

But maybe you can have your cake and eat it too. The Smart Torque option on several Cummins engine models is an inexpensive programming feature that can limit torque output in lower gears-where it’s most threatening to drivelines-and thus allow you to spec a lesser driveshaft and axle. That could mean ordering a 40,000-pound tandem instead of a 46,000-pound model in the case of a 600-horse engine, for instance.

THE OTHER BITS

Fuel is mighty heavy, so do you need twin 150-gallon tanks? And even if you have smaller, lighter tanks, do they need to be full all the time? There’s hundreds of pounds to be gained here.

How about 22.5-inch tires and wheels instead of 24.5? Again, the difference is hundreds of pounds. Aluminum wheels may make sense, but they can be costly. You can get aluminum hubs too, saving 110 pounds per tandem in the case of a lightweight Meritor product.

Even small items like air compressors can represent substantial weight savings. The new Bendix DuraFlo 596 is a direct replacement for the company’s Tu Flo-1400 compressor on Series 60 engines, for example, but it’s 45 pounds lighter.

As with any other spec’ing matter, a careful approach is called for here. The key is to make sure that any extra money you spend to lose weight is going to be paid back in lower costs and/or higher revenue. It demands a cost-per-pound analysis.