Posted on 12-09-2012
Filed Under (Uncategorized) by Chloe Davies

Thanks to the advent of electronic all-wheel drive systems, modern beetle-crushers are extraordinarily competent. You no longer need to be an experienced bundu-basher to get out there – way out there.

And, of course, you’ll want to take along all the creature comforts without which Herself will not set one pedicured foot beyond the pavement – and that means lugging a trailer.

On the face of it, no problemo. Your luxury 4×4 with electronic everything has torque to spare for towing, and there are super-tough off-road trailers on the market that take the rough even better than the smooth.

But there is a weak point – right in the middle.

Towbar manufacturers are warning that extreme off-road manoeuvres with a trailer attached can stress the towbar – or the tow vehicle – beyond their design limits, and in some cases can force the vehicle and trailer to interact in a way which they were never designed to do.

Thule Towing Systems managing director Mark Gutridge explained: “A towbar has to able to handle a deflection of 15 degrees above or below the horizontal (and a lot of them can do better) but in certain situations you could flex the rig a lot more than the towbar can deal with.

“If you go beyond that – especially when the trailer is hanging down such as when you go over a crest – then the hinging effect is lost and the two vehicles effectively lock together, transferring the forces directly into the chassis of the 4×4 or the frame of the trailer.”

INSTANT PROBLEMS

Depending on how strong the components are, the towbar may break, it its mountings points may rip out of the chassis, or it could actually fracture the ball – usually at the narrowest part of the neck.

“In a worst case scenario, such as when you’re climbing out of a donga with very steep sides, the trailer can literally hang on the ball, to the point where the trailer wheels are off the ground,” said Gutridge.

“A similar thing can also happen when going through an ‘axle-twisters’, when you get a lateral twist of more than 25 degrees, which is what the ball is designed for.”

WALK IT FIRST

By its very nature, 4x4ing involves venturing into the unknown but you need to be aware that there are limitations to each link of the chain, even if you’re pulling a proper off-road trailer with big wheels and the appropriate tyres.

If you encounter a serious obstacle, walk it first; if you think it will twist or bend the coupling between the tow vehicle and trailer beyond the angles mentioned here, rather try another route.

Gutridge warned: “Damage caused by this kind of overloading doesn’t always show up immediately, but if you put something under extreme stress, sooner or later it will fail, with disastrous consequences.”

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