Stuff Carrying Capacity and Maximum Range
February 21, 2020
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The plan is for Molly to take us and all of our stuff to some of the most remote places in the world. But just how much stuff can we take and just how far can we go? In this blog post we explore these questions in a little detail.

Payload Calculation

Payload is the general term used to measure how much stuff you can safely carry. Available payload is easy to calculate and is the maximum gross vehicle weight rating (GVWR) of the truck less the weight of the truck itself. The GVWR specifies the maximum legal limit the truck can weigh and still remain safe. While the weight of the truck is obviously the weight of the truck, it is worth noting it is measured without people and any stuff (or payload), but does include all required fluids like coolant and transmission oil and with a full fuel tank. This truck weight is also known as the curb weight. In our case, we include the weight of the Earthcruiser house and consider all of the bolted down parts of the truck as part of the truck. Of course the house is empty of any food, clothes, camping equipment, toys; basically all of our stuff. With these definitions and calculation, Available Payload is thus a weight measure of all the stuff we can take safely.

All ratings are for a moving load, usually on a highway. The forces exerted on the truck when moving are much higher than when it is sitting still.

Available Payload is a little more complicated than the above description. Not only can the GVWR not be exceeded, but there are also ratings for the front and rear axles which can’t be exceeded. And then there are also the tires, they also have a maximum weight rating.

Scott and Matt have an excellent talk about the importance of managing Payload in their podcast on Expedition Portal. And Tom Shepard in his Vehicle-dependent Expedition Guide opens the vehicle selection section with a discussion on Payload. The tl:dr summary; Payload considerations are very important.

Gross Vehicle Weight and other Ratings

Let’s start with what the FUSO Canter FG4x4 is rated for in the USA. Here are the specifications from the manufacturer, all of which are maximums:

  • GVWR = 14,050 lb. / 6,373 kgs.
  • Front GAWR = 5,730 lb. / 2,599 kgs (or maybe 6,175 lb. / 2,801 kgs)
  • Rear GAWR = 9,480 lb. / 4,300 kgs.

The above ratings are for highway driving, and can be lowered by as much as 20% for off-highway use. Earthcruiser has modified and upgraded suspension and springs, and, as a second stage manufacturer, put their own GVW rating sticker on the truck. Earthcruiser knows the vehicle will be used off-road, and their sticker lowers the various ratings to

  • GVWR = 13,050 lb. / 6,919 kgs.
  • Front GAWR = 6,175 lb. / 2,800 kgs
  • Rear GAWR = 7,716 lb. / 3,500 kgs.

The tires also have a maximum weight rating. We have Toyo Open Country M/T tires LT 315/75R16 which have Load/Speed rating of 127Q which converts to 3,858 lbs / 1,750 kgs per tire and 99 mph / 160 kph. If you do the math the good news is that these tires do not as a practical matter further limit the GVWR or axle ratings.

Available Payload

Now that we know the safe maximums, it is easy to calculate the Available Payload. We just need to establish the truck weight, and this is easy, all we need to do is weigh Molly (unloaded of course). At the time we took ownership of Molly, the truck weight was recorded on the Certificate of Origin as 10,300 lbs / 4,672 kgs. But for good measure, we weighed Molly at a public scale, with the following results (ok, we plan to weigh Molly soon)

  • Vehicle Weight = xx,xxx lb. / x,xxx kgs.
  • Weight on Front Axle = xx,xxx lb. / x,xxx kgs
  • Weight on Front Axle = xx,xxx lb. / x,xxx kgs.

And in the meantime, based on the Certification of Origin, the Available Payload of Molly is 2,750 lbs. / 1,250 kgs. And now we have the budget for all of our stuff.

Spending the Payload Budget

Our budget includes the following

  • Us
  • Fresh water tanks filled (70 gallons / 265 l)
  • Grey water tank filled (20 gallons / 75.7 l)
  • Toilet, Black and Flush Water filled (9.1 gallons / 34.3 l)
  • Clothes
  • Food
  • Tools, Spare Parts and Recovery Gear
  • Assorted electronics

Without getting into the exact budget amounts, we are below the Payload. Yay, we have enough spare weight capacity to have a few friends over for dinner. Staying within ratings just makes sense. Shout-out to Earthcruiser for getting this right.

Range vs Payload

There is a relationship between Range and Payload. More fuel, more fresh water, more food all means more range, but it also means less available payload. Molly has 63 gallons of fuel, giving an effective range of 800 miles or 1,300 kms. All dependent on the terrain and driving conditions of course. In Sterlin we had a range closer to 300 miles or 500 kms (without our Jerry cans), and never had issues finding fuel.

The 70 gallons of freshwater gives us a range of about 2 weeks between refills, again dependent on the conditions. Could probably stretch it out to 3 weeks if we really needed to. We can certainly carry enough food for 2 or 3 weeks in our payload budget.

Future Considerations

There are a few components on Molly that could be changed in the future, to further increase the available payload. We have two Mastervolt 12/270 Group Super 8D Sealed Marine Batteries each with weight of 161 lbs / 73 kgs. These could be replaced with, for example, Victron Energy 12,8V Lithium SuperPack batteries with a weight of between 66 lbs / 30 kgs for a potential payload gain of 190 lbs / 86 kgs. The roof rack above the cab could also probably shed another 40 lbs / 20 kgs by placing it on a small diet.