Thule has warned off-road fans who attempt extreme manoeuvres with a trailer in tow that such exploits could stretch the tow bar and tow vehicle beyond their design limits. Thule Towing Systems SA suggested that certain extreme off-road manoeuvres could force the vehicle and trailer to interact in ways they were nod designed to.RIG, TOWBAR AND TOWBALLThule‘s managing director Mark Gutridge said: “The engineering specification for towballs states that they must be capable of handling a 15-degree rotation above or below a horizontal line relative to the trailer, though depending on the coupling design you could theoretically achieve more in certain situations. “Generally, though, if you go beyond that - especially when the trailer is hanging down such as when the vehicle traverses a crest - then the hinging effect is lost and the two units effectively lock together and transfer forces directly into the chassis of the car and/or the frame of the trailer,” Gutridge explained.This could have a dire effect on not only the rig but also the towbar and the tow ball, Thule said. "The towbar might break, its mounting points might be ripped from the chassis, or the towball could be damaged – usually at the narrowest part of the neck just below the ball itself. “In a worst-case scenario, such as when the rig is exiting a donga with very steep sides,” Gutridge said, “you could have a situation where a trailer literally hangs on the ball, to the point where the trailer wheels are off the ground. “A similar situation could occur when negotiating ‘axle-twisters’ and a lateral twist of no more than 25-degrees from the vertical is what the ball is designed for.”OFF-ROAD TRAILER TIPS Thule said 4x4ing often involved venturing into the unknown but, even if you’re pulling a proper off-road trailer with big wheels and the appropriate tyres, there are still certain limitations to consider. Thule advises that, should you encounter a serious obstacle while towing, first investigate it on foot. If there are any doubts about whether the coupling between the tow vehicle and trailer will be twisted or bent beyond their limits, try another route. “Damage caused by this kind of overloading doesn’t always show immediately and a catastrophic failure can happen much later, with disastrous consequences,” Gutridge concluded.