There’s no doubt about. When it comes to matching a truck with a truck camper, the center of gravity is often overlooked. Sure, it’s important that the truck’s GVWR and payload rating are up to the job, but ignoring the center of gravity can not only cause drivability issues but can also cause catastrophic damage to your truck. Fortunately, a good number of truck camper owners are familiar with the term and know how to determine it. If you aren’t familiar with the term, no problem. In this article, we’ll not only discuss what the center of gravity is, but we’ll also discuss why it’s important to your safety and to the longevity of your truck.
What is a truck camper’s center of gravity (COG)? It’s simply the balance point or where most of the truck camper’s weight sits. It’s supposed to take into account everything inside the camper including full holding tanks. Typically, the COG is marked with a sticker that has been affixed to both the driver and passenger sides of the camper. If a COG sticker can’t be found, don’t fret. This number in inches, which is usually measured from the lower front of the camper, can usually be found on the manufacturer’s website, though some manufacturers will also include a COG measurement from the rear of the camper as well.
How does the COG of a camper relate to your truck? Ideally, the camper’s COG of gravity should be located in front of your truck’s rear axle—in most cases 10 to 20 percent of the weight will be on the front axle and 80-90 percent on the rear axle. Doing this ensures a safer driving experience and less wear and tear on the frame of your truck. Furthermore, placing the COG behind the rear axle should be avoided at all costs because it does two things. First, it takes weight off of the front axle, creating “drivability” issues with steering and braking. Second, tension is created in the center of the frame that can result in a catastrophic failure.
Having built over one hundred rigs over the years, Mark Cymbaluk, owner and CEO of Overland Explorer Vehicles (OEV), is an expert on truck camper loading. He’s noticed an alarming trend lately all showing the same thing—compromised truck frames from loading the chassis incorrectly.
“In all reality, you can be a bit heavy on most chassis and get away with it—for a while,” Cymbaluk said. “You should always adhere to GVWR and GAWR weights, but what will catch you in more ways than one is loading the chassis aft of the rear axle. There is not a truck manufactured today—commercially or privately—that is designed with a chassis that is meant to be in tension. When you load a chassis heavy behind the rear wheels, (and a degree of this applies to load COG directly above the axle centerline as far as vibration and harmonics are concerned), you unload the front axle. In this case the load point designed in the center of the chassis goes into a tension moment, you basically have a heavy weight using the rear axle as a fulcrum to lift the front axle, along with it a heavy engine.”
Of course, hauling and towing trailers with an inordinate amount of tongue weight can amplify this tension to the frame even more, resulting in cracked truck frames. There are countless examples of this happening over the years to trucks of all ratings. One recent incident involved a Ford F450 hauling a large Okanagan truck camper and towing a large utility trailer loaded with tools. A more recent example that went viral involved an overloaded Ram 3500 DRW hauling an Eagle Cap 1165.
“When this [fulcrum affect] happens you take the frame from an level unladen stance, and ‘bow’ the center up,” Cumbaluk explains. “Now you drive down the road, you have a higher COG due to the load, this amplifies the moment on the chassis under tension, it basically flexes up and down much further than a properly loaded chassis as it starts out with upward deflection the moment the camper is put on. This moment is enhanced by the natural direction of travel, braking, accelerating, terrain, torque reaction, etc. Now add rough roads, vibration, harmonics, maybe a bolt hole with a sharp edge, the heat affected zone near a cross member (inherent stress point), etc. and the beginning of the end has started, the chassis is experiencing far more motion than it was designed for, continuously. This is a 100 percent duty cycle, in the wrong direction of intended loading.”
So how can you tell if your COG is “bad” or “off”? It’s fairly easy, though it will take a couple of trips to a local CAT Scale to determine it: one visit without the camper, the second visit with the camper mounted. Simply put, if your front axle weighs less with your truck camper mounted then your rig’s COG is bad or off and needs to be corrected.
How is correcting a “bad” center of gravity done? Heavier items should be stored in front of the rear axle, not behind it. This is true whether your camper is a pop-up or a hard-side, a chassis-mount or a topper. Take a close look at all storage compartments and how things are stored. If you have a large double- or triple-slide camper, don’t forget about that rear storage compartment with the convenient pull-out tray. Fight the urge to place heavier items where they can easily be reached if this places them behind the rear axle. And don’t forget about that aftermarket truck bed if you have one. They’re also part of the center of gravity equation. Correctly loading them is important too.
Of course, smaller trucks with thinner, less robust frames are affected by this dynamic too. “This kind of thing is not new, simply Google “truck broken frame” and see what pops up,” Cybaluk said. “The Aussie and African rigs have been doing this for a long time! There are a ton of Hilux’s with broken frames, short wheel base with long loads, all bent and broken the same way, rear on the ground. From real world experience, and a lot of it on the Toyota HZJ platform, I can tell you that the Tundra and Tacoma do not hold a candle to the HZJ chassis or payload. I get the argument for off-road capability, I do. But that would only apply in reality to an empty truck, a properly loaded truck will perform better in all aspects than an improperly loaded unit, and guess what? You are just as long regardless of the wheel base.”
At the heart of the matter is getting the right truck for your camper. If you have your heart set on a certain camper, it’s imperative to buy the right truck to begin with. An adequate amount of payload is paramount, of course, but the bed-length also needs to be considered as well since the wheelbase plays a major role in the COG calculation. Both truck camper owners and upfitters need to keep this in mind when considering aftermarket upgrades. Obviously, this includes aftermarket truck beds.
“As overlanding is becoming so prevalent, with truck camper sales accelerating, and a pile of builders/upfitters popping up, it would be nice to see more builders adhering to some standard weight and balance practices that are industry standard for commercial upfitters. There’s a very solid reason these procedures have been implemented into law. We get requests every day from the guy with the 5.5-foot short-box looking for a 8-foot tray, we turn them down for those reasons, and even after explaining why, we are the bad guy. Not one of those builds would pass a weight and balance program as specified under Federal Motor Vehicle Safety Standards and Canadian Motor Vehicle Safety Standards, these are pretty basic requirements, but the benefits to the safety of the end user, as well as everyone else on the road are immense,” Cymbaluk said.