Truck News


Spec’ing Fifth Wheels

CALGARY, Alta. - When making a truck purchase, spec'ing the right fifth wheel for your application is one of the most important considerations - and not only from a safety standpoint.

CALGARY, Alta. – When making a truck purchase, spec’ing the right fifth wheel for your application is one of the most important considerations – and not only from a safety standpoint.

Not only is your fifth wheel the only thing linking your truck to the trailer and cargo, but a good fifth wheel can deliver a smoother ride whether you’re loaded or empty.

And thanks to numerous developments in fifth wheel technology in recent years, there are now a wide range of options for fleets and owner/operators.

No- or low-lube fifth wheels

Several fifth wheel manufacturers have introduced low-maintenance products that use lube-free polyurethane top plates, which eliminate the need to grease the top plate. Still, manufacturers warn these top plates may not be the best option for all applications.

“They are a wear item,” says Ward Kolpack, Fontaine’s executive director of marketing. “If you get into a very dirty off-road application you’re going to get a lot of debris in these and it’ll tear them up.”

For the most part, the polyurethane plates are only recommended for on-highway applications, he says.

Also, Kolpack points out, drivers can tear the top plate if they perform a bad coupling, so they are best suited for applications that don’t require frequent coupling and uncoupling.

Greg Laarman, vice-president of engineering with Jost International, agrees.

“Our recommendation is that they are used for low-coupling frequency applications or if it’s a totally married application,” he says.

“If there’s a lot of coupling and uncoupling, the potential for damage to the low-lube surfaces would be so great that the risk would probably outweigh the benefits of buying the product.”

No-lube fifth wheels using laser-resurfacing technology are available from Holland, which eliminate the need for lubricating any of the fifth wheel’s parts. The complex technology involves lasers which recreate metal surfaces by melting a small depth of surface as new materials are added to create a new surface area.

“This technology means that a customer no longer needs to grease the top plate, locks or brackets of a Holland 3500 Series No Lube fifth wheel,” says Holland’s Scott Fowler.

What materials work best?

Fifth wheels comprised of a variety of different materials are available, so just which material works best depends on whom you talk to.

Doug Dorn, fifth wheel marketing manager with Holland is adamant that cast steel is the way to go for top plates.

“A cast steel top plate is superior, both in the weight versus strength trade-off and also in the impact resistance area,” he claims. “Pound for pound, we feel a properly designed and manufactured cast steel top plate provides for a significantly more robust fifth wheel than alternative materials and also allows for maximum weight reduction while maintaining maximum durability.”

One of those alternative materials is cast ductile iron.

“Ductile iron has some benefits but we find its weaknesses outweigh its benefits,” Dorn says. “Generally it requires a lot more ductile iron material to get the same type of impact resistance and same type of durability that cast steel provides.”

Con-Met also uses cast-steel for its fifth wheel products. Fleet sales manager Al Anderson says there are several advantages to the material.

“With ductile iron they have to use a wear collar in the throat of the fifth wheel because ductile by nature is fairly soft so you’ll get a lot of premature wear in the throat if you don’t have a wear collar,” Anderson explains. “We feel cast steel lasts the longest and is more durable.”

Jost’s Laarman, however, feels ductile iron delivers the best results. He says pockets on the surface of a cast ductile iron top plate provide reservoirs for the grease resulting in better lubrication than cast steel. He also argues the ductile iron top plates provide more flex without cracking than their cast steel counterparts.

In addition to offering a cast steel top plate, Fontaine has a pressed steel product.

“(The pressed steel) top plate allows us to put different steel strengths where it’s needed rather than using one whole cast,” Kolpack says. “Some people think cast is stronger than (pressed) steel but it’s not true. But some people have that perception so we offer both products.”

Sliding vs. stationary

Another key consideration is whether your application would be best served by a sliding or stationary fifth wheel. A sliding fifth wheel costs more, but it delivers a better ride while bobtailing. It also allows the operator to better distribute the weight of the load. And it adds to the resale value of your truck.

Laarman estimates between 60 and 65 per cent of trucks on the road today feature a sliding fifth wheel. The slider is particularly popular among owner/operators.

But some large fleets are beginning to favour stationary fifth wheels since they are less expensive and they are ideal for applications where the same product is being hauled along similar routes, he adds. The stationary designs also tend to be lighter which of course can result in better payload capacity.

Con-Met’s Anderson also says he’s seen fleets shifting towards stationary fifth wheels within the past few years.

“I’m seeing a movement towards more fixed fifth wheels because trucking companies look at saving weight and saving cost and everything being more standardized. So I’m seeing a lot more people using fixed fifth wheels than I used to,” he says.

But O/Os are sticking with the sliding designs, he says.

“It’s the nature of the beast. Owner/operators may be leased to one company one day and another one the next day and hauling one trailer one day and another trailer the next day. So they need to be a little bit more flexible in their applications,” says Anderson.

Watching your weight

As with most components, weight is also an important consideration when spec’ing fifth wheels.

But the experts are divided on just how important it should be. There’s the fact that manufacturers have to meet stringent safety standards, which makes taking weight off that much more difficult.

And some experts even say weight shouldn’t be the most important consideration.

Kolpack says some fifth wheel makers are simply making their product smaller in an effort to reduce weight.

“Some manufacturers are taking weight out by reducing the footprint or the circumference of the fifth wheel,” Kolpack says.

“You can take a lot of weight out simply by making something smaller but smaller isn’t always better.”

New trailers won’t always sit properly on a fifth wheel that doesn’t have broad enough shoulders, Kolpack says. But Con-Met’s Anderson says weight is still something worth thinking about.

“It’s a pretty heavy piece of equipment so they should be aware of the weight,” he warns.

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