Bull­dust DEAN MEL­LOR

4 x 4 Australia - - Contents - DEAN MEL­LOR

Back in the mid-1990s, the max­i­mum braked tow­ing ca­pac­ity of most pop­u­lar large wag­ons in­clud­ing the 80 Se­ries Land Cruiser and GQ Pa­trol was 2500kg, while many of the dual-cab 4x4 utes such as the Toy­ota Hilux and Nis­san Navara were, quite sen­si­bly, rated to han­dle a max­i­mum braked trailer weight of only 1500kg.

To­day, if a 4x4 doesn’t have a braked tow­ing ca­pac­ity of more than 3000kg, it’s sim­ply not in the game, dual-cab utes in­cluded. How has this mas­sive in­crease in tow­ing ca­pac­ity been achieved?

Logic would sug­gest four-wheel drive man­u­fac­tur­ers are now us­ing stronger ma­te­ri­als, cut­ting-edge de­sign and beefier con­struc­tion tech­niques to more than dou­ble the braked tow­ing ca­pac­ity of the lat­est gen­er­a­tion of 4x4 utes, but poke your head be­neath one and you won’t spot any sig­nif­i­cant changes to chas­sis de­sign or sus­pen­sion and brak­ing com­po­nents. Nope, most mod­ern 4x4 utes are still run­ning a sep­a­rate chas­sis, leaf springs, live axle rear-ends and disc/drum brake set-ups.

It’s in­ter­est­ing to com­pare the mod­est pay­load in­creases achieved over the past 20 years to the mas­sive tow­ing­ca­pac­ity in­creases. Com­par­ing a basespec 1995-model Navara dual-cab ute with its mod­ern equiv­a­lent, pay­load has in­creased by just 24kg (from 1010kg to 1034kg) while braked tow­ing ca­pac­ity is up a stag­ger­ing 2000kg (from 1500kg to 3500kg). In the case of a base-spec Hilux over the same pe­riod, pay­load has de­creased by a whop­ping 245kg (from 1165kg to 920kg) while braked tow­ing ca­pac­ity has more than dou­bled from 1500kg to 3200kg.

You might think the ve­hi­cle man­u­fac­tur­ers use a specif­i­cally leg­is­lated for­mula to cal­cu­late a ve­hi­cle’s max­i­mum tow­ing ca­pac­ity, but in truth they are left to their own de­vices to set tow­ing weights. Fac­tors they take into ac­count in­clude ve­hi­cle de­sign, en­gine out­put, axle ca­pac­ity, tyre rat­ings and the ef­fect that trailer weight will have on the ve­hi­cle’s sta­bil­ity and over­all dura­bil­ity when tow­ing. It’s likely the mar­ket­ing teams have in­put as well – maybe not the fi­nal say, but def­i­nitely some sig­nif­i­cant in­flu­ence.

While hardly any­one will ever hitch a 3.5-tonne trailer to the back of a Navara, Ranger, Colorado, D-max or BT-50, the fact that the ve­hi­cle man­u­fac­tur­ers say they can is a bit of a worry. After all, hang­ing that much weight off the back of a ute that only weighs two tonnes is hardly a recipe for a sta­ble set-up, es­pe­cially when you con­sider all that weight is con­nected to a hitch that is a me­tre or so be­hind the rear axle.

When I was first tasked with con­duct­ing a tow­ing test back in 1995, I didn’t have a hell of lot of ex­pe­ri­ence with trail­ers. Sure, I’d oc­ca­sion­ally bor­rowed the old man’s box trailer to drag my dirt bike out to the scrub for a ride, but that was about it. Yet here I was, cruis­ing down the Princes High­way with a two-tonne boat and tan­dem-axle trailer hooked up be­hind ve­hi­cles in­clud­ing an 80 Se­ries Land Cruiser, a GQ Pa­trol, a Dis­cov­ery and a Pa­jero. For­tu­nately I had sense enough to know the key to suc­cess­fully tow­ing such a size­able set-up was to keep things smooth – no hard ac­cel­er­a­tion, no stomp­ing on the brakes and no sud­den changes of di­rec­tion.

Nev­er­the­less, I had a few mo­ments over the week of test­ing, and at one time al­most got it all crossed up try­ing to stop at a set of traf­fic lights that were about to turn red. Luck­ily the braked tow­ing ca­pac­ity stan­dard back then was 2500kg and not 3500kg, be­cause I reckon if I’d had an ex­tra tonne be­hind me I would have been stuffed.

On the pos­i­tive side, mod­ern four­wheel drives (even utes) are equipped with a num­ber of elec­tronic safety aids that greatly ben­e­fit tow­ing, such as ABS, elec­tronic trac­tion con­trol, sta­bil­ity con­trol and, in many ve­hi­cles, trailer sway con­trol. Trailer sway con­trol uses sen­sors in the ve­hi­cle – such as for steer­ing in­put and ve­hi­cle yaw – and a mix of en­gine out­put and brake con­trol to sup­press lat­eral move­ment that can be caused by a va­ri­ety of fac­tors in­clud­ing cross­winds, changes in road sur­face and steer­ing in­put. It’s prob­a­bly the great­est ad­vance­ment in tow­ing safety over the past 20 years.

Ob­vi­ously, be­cause it seems that noth­ing much else has changed.

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