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.

NZ4WD - - CONTENTS - Story by Mur­ray Tay­lor. Photos NZ4WD file.

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?

First prin­ci­ples

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.

Weighty mat­ters

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.

NZ4WD rec­om­mends

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.

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