DO YOU NEED TO DIET?
If your family 4x4 or work ute is ‘packed to the gunwales’ it could easily exceed its recommended carrying capacity. Murray Taylor explains why.
More is better, right? Back in the day you and your mates might have been happy to head off into the great outdoors with little more than an egg sandwich and change of underwear ( if you were lucky). These days though, well, some of us do literally take the kitchen sink with us don’t we? Which is all well and good if you have done your maths and purchased the correct beast for the job... “Eh?” I hear you ask? If it looks like a ‘ Tuff Truck’ surely it IS tough. And if it has an advertised Tare mass of on or about 1000kgs isn’t that how much I can carry?
Hmm. Looks like we need to go back to first principles here. To do so I will do some simple sums on a heavy 4WD. First we need to know the GVM ( Gross Vehicle Mass), then the Tare Mass. You should be able to find both in the manual or a spec sheet, and it’s worth knowing that usually the Tare ( or unladen mass) figure only includes 10 litres of fuel). To calculate how big a load your vehicle can safely carry simply subtract the Tare mass figure from the GVM one. In my “heavy 4WD”, (a typical five-door wagon) case the GVM is 3,000 kg and the Tare Mass 2,150kg, which leaves a total of 850kg to play with. Or does it? Let’s look at the weight of the fuel when the 90 litre tank is filled. Google “how much does diesel weigh per litre?” and the answer is “about 0.832kg”. Multiply 90 x
0.832 and you get 75kg. So we are down below the 800kg mark already, and that’s before we start adding the weight of the, er, add-ons.
In my hypothetical cas’ the figures would be: Bullbar 17kg. Winch 33kg. Extra battery 20kg. Side bars 10kg. Tow bar 20kg. Recovery hooks 3.6kg. Drawer system 15kg. Lift 2inch 20kg. Larger tyres 29kg. Recovery gear: Strop 2.5kg. Extension 1.8kg. Shackles Misc 18kg. Hi Lift Jack 13.2kg. Shovel/ Spade 3kg. Vehicle parts/ tools 15kg. Socket Set 7.2kg. Compressor 8.2kg. Fire extinguisher 2 x 0.9kg = 4kg. Looked at individually a kg here and a kg there isn’t something to lose sleep over. What is, is the 315.5kg you get when you add them all together.
And don’t forget…
Who would have thought it when we had 850kg to play at the start? We now have just 489.5kg to play with: the amounts going down fast… To whit: A fairly typical set (mine!) of camping gear including; Tent (large) 20kg. Camp stretcher (x 2) 13.4kg. Folding chair (x 2) 5.8kg. Camping table (small) 3kg. Cooking gear 7.5kg. Sleeping bags (x2) 6kg. Personal gear etc 25kg. Camera and electronics 7.5kg. That’s another 88.2kg we’ve just put into the beast, leaving us with 401.3kg for whatever else we want to put in, or on, the 4WD in question. At the end of the day it’s not a lot. Mum and dad at around 180kg the pair, and two children at 120kg but here’s the rub – that only leaves 103kg for all the extra gear and food you need for an “industry standard” family of four. And that’s forgetting about the trailer you may have on behind, or the roof rack with a top box, or the extra 40L of fuel you might well be carrying up top.
Makes you think
If nothing else it certainly makes you think about the actual total mass of the vehicle in question, and maybe why it no longer wants to stop on a dime, or why the fuel consumption’s gone out the window on that long trip! It’s not an issue solely affecting safari-ready “Tuff Trucks” either. What about a nice new modern SUV: we are seeing more and more of on tag-a-long Safaris these days. A little website detective work produces these numbers. Vehicle X – GVM 2,750 and a Tare Mass of 2,075 kg, so that’s a payload capacity of 675 kg before we start. We’ll forget the mods this time and just add the minimum we need. To whit: Diesel ( 55L tare includes 10L) 45.7kg. Front hooks 2.4kg. Tow Bar 15kg. Shackle for rear 1.0kg. Strop 2.5kg. Fire Extinguisher 2x.9kg = 4.0kg. Spade 3.0kg. First Aid kit .05kg. That’s about all one needs for a safari in regard to gear, so that’s 73.5kg, leaving us with 601.5 kg for the camping gear. Using our pervious figure for the camping gear (two people) we are now left with 512kg as the payload left for the vehicle. And, if – for argument’s sake – you put four adults along with the extra gear for another two adults into this nice modern SUV, along with food etc, there’s not a lot left to play with in regard to surplus payload – especially if you add a few extras to turn it into a more capable vehicle off-road. I haven’t forgotten about utes either. These days your typical modern turbo-diesel double-cab/wellside ute is almost the de facto 4WD, with a typical GVM of 3,000kg and Tare Mass of 2,100kg. Utes like these will give you some extra payload, but they are also the ones most likely to be kitted out with all those “musthave” extras such as front bar, added side protection, winch, lift to fit those bigger tyres, canopy or hard cover to protect all the other goodies one carries around etc. So, particularly if you go the whole hog with your add-ons, the story – in terms of a reduction in legal carrying capacity – will be similar to the “Tuff Truck” and SUV examples I have quoted.
And what about towing?
Please also note that I have not covered what happens when you tow a heavy trailer, but the recommendation is that seven to 10 percent of the trailer’s GVM is loaded onto the tow ball of the towing vehicle. So if towing, the overall ( safe, legal carrying) capacity of the tow vehicle is reduced by the amount on the tow ball. Which just adds to what you have to remember when loading a vehicle.
Before you head off on your next safari, I recommend that you put your (fully-loaded) 4WD across a weigh bridge. Not only will this help you get your tyre pressures under control for the actual loaded vehicle, it will also help you accept that it’s bloody heavy!. Having done this exercise on my own vehicles, I understand why it’s also always recommended to remove all you can from a vehicle when it’s not required because you certainly will save on fuel and tyre life.