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Gross Vehicle Weight – Why it matters !

Gross Vehicle Weight – Why it matters !

Gross Vehicle Weight, Kerb Weight & overall Payload.
Critical informations all too often ignored when buying or organising an off-road vehicle for an overland trip. In this article we tell you what it all means and what it implies…

 

Before digging into the technical aspects of this overall concept, lets take a small example which I believe will illustrate the following technical points of our subject perfectly.

Take a bicycle and go for a ride. In this scenario the bike is your vehicle and you happen to be its engine. Along the way find a hill to climb with a decent elevation percentage, one you know the “engine capacity” aka your level of fitness can overcome without too much pressure. Once done, get back down and climb it again, but this time with a friend – aka a dead weight – sitting behind you. First thing you will notice is that the extra weight of your friend is putting unwanted pressure on your bike. Its frame, suspensions, tires are not appreciating this extra load, which puts it at a much greater risk of breaking. The second and most obvious observation is that climbing that hill is now much harder, if not impossible, given the power of the “engine”. Your friend is just too heavy for you and your bicycle, and if you want to keep on climbing you better stick to a weight you and the frame can sustain. That weight is what we call your payload.

What applies to you, in this particular case in obvious manner, applies just the same to your car and its engine. The only reason why most of us fail to realize it, is simply because we are passive to the effort when driving, unaware of the struggles endured by our beloved rig, as it tries to transport the dead weight we imposed on it.

Luckily, manufacturers in their wisdom, after many specific performance tests have established for you the most weight your vehicle can carry along. They called it the Gross Vehicle Weight or GVW. Now that number is useless on its own. To be effective you need to deduct the original weight of the car, also called Kerb (or curb) Weight to find out how much you can “charge the mule” !

GVW – Kerb = Payload.

Now let’s take my car as a concrete example.

I have a 2012 Jeep Wrangler Unlimited CRD. The brochure mentions Curb Weight 2128 kg / 2238 kg.
Ok, why two numbers here ? Just for the sake of making thing more confusing ? No, most manufacturers will give you both numbers. The smaller one is the weight of your vehicle without gas and driver. The second is the estimation made by the vehicle manufacturer with a full gas tank and a 75 kg driver. Two reasons to take the smaller number as a reference: First, not all of us weight 75 kg with clothes on. Second, manufacturers often take liberties with their estimates. In the case of my Jeep, their estimate puts the weight of Diesel fuel at 0.42 kg/L, while in reality it stands at 0.83 kg/L. That’s a 36 kg cheat in the case of a full tank.
On the other end of the spectrum, my car’s GVW is 2506 kg. As per our formula above, it then goes as follow:

GVW 2506 kg – 2128 kg = 378 kg

You have a payload of 378 kg on this particular vehicle. In other words, if you put in 379 kg, you won’t reach the top of that hill ! Got it ?

Now, could sound like a lot of weight for the novice that I was when I bought my car. As a matter of fact, like most people, I didn’t even paid attention to it. And that turned out to be a mistake !
378 kg as a payload is nothing, which is why I can claim as a fact that Jeeps where not conceived as overlanding vehicles. My comments offend your tribalism ? Just compare with the 1.000 kg payload of a Toyota LC 78 Wagon for example and get back to me !

Let’s use another concrete example, a trip a did recently off-roading around Oman called the Oman trail, and let’s start deducting from the available payload the necessary weight I needed to bring along to complete that journey safely:

Available Payload: 378 kg

– My weight fully dressed: 75 kg
Left 303 kg.
– My tank capacity is 85.17 L. Total weight filled with Diesel: 71 kg
Left 232 kg.
– My average range when off-roading is 25L/100km, in other words 340 kms of autonomy. Not enough to cross the desert. I needed 80 L extra + the weight of the extra tanks. Total: 75 kg
Left 157 kg.
– I needed to carry water. One 20 L spare plus a 6 pack of 1l drinking water bottles. Total: 27 kg
Left 130 kg.
– I have a winch: 40 kg (not shown on the picture)
Left 90 kg.
– Car spare, tool box, fluids, etc…: 10 kg
Left 80 kg.
– Camping gears and clothes: 5 kg (yes I go light!)
Left 75 kg.
– I have photo equipment & electronics: 12 kg
Left 62 kg.
-I need some food: 2 kg
Left 60 kg.

Total left so far: 60 kg.

That leaves me with just enough room for my wife and her bags if she wanted to join me for the ride !

As you can see my available payload allows me for very little extra. Forget a roof rack, a roof tent, a fully equipped gas kitchen, and all the other frills you may see on fully customized vehicles.

Off-roading is already putting a lot of stress of your car, often pushing it to its limits. The last thing you should do is making it even worse and take unnecessary chances. Pay very close attention to your car max payload, may it be the original spec or the new one you have achieved through various component modifications (New suspension, engine boost, etc). Know the weight of every item you installed on you car, (winch, extra lights, roof rack, roof tent, extra tank, interior cargo, etc…). Take into consideration the weight of your passengers and what they bring along as it adds to your own weight and your belongings. Make a list, add the numbers and see where you stand.

Yes, there are far better options than my Jeep when it comes to payload capacity. As mentioned, Toyota Land Cruiser, or Land Rover Defender offer a much better capacity, which theoretically would allow you to bring along a lot more useless items. But to be honest, less is always more, and in the end you should always try to keep things to a minimum, no matter what is your margin. The car will always perform better the lighter it stays.

Happy travels.

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