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Motoring Top Stories

Top eight towing myths busted

CarsGuide logo CarsGuide 20/05/2017 Mark Oastler

© CarsGuide.com.au Everyone loves to see a long-standing, widely accepted myth well and truly busted.

To the point where two nerdy blokes in San Francisco made a handy global TV career out of it. And when it comes to towing, plenty of conventional wisdom, handed down through generations, is ripe for factual investigation. Join us as we bust eight commonly held towing myth-conceptions.

1 - A 3.5 tonne towing capacity means just that

There’s plenty of chest-beating about 3.5 tonne (3500kg) towing capacities in vehicle advertising these days, but the figure you really need to focus on is the GCM or gross combined mass, because that determines the maximum legal weight or ‘mass’ of your vehicle and trailer combined. You might be shocked to discover that to tow 3500kg you need to reduce your tow vehicle’s payload by up to 500kg in some cases to stay below the GCM limit. Your owner’s handbook is your best friend.

2 - You can decrease the tow-ball download by shifting more of the trailer’s load to the rear

Makes sense if you’re parked at a rest stop. However, if you’re towing and your trailer is hit by a strong gust of wind or you have to swerve suddenly, carrying too much weight behind its axle line can allow the rear of the trailer to start behaving like a pendulum in the horizontal plane, swinging the rear of the trailer from side to side in ever-increasing arcs, with ever-increasing danger. So carry as much of your trailer’s load on – or as close to - its axle line as you can. And get it as low as you can, to lower the centre of gravity for greater all-round stability. 

3 - You can decrease the tow-ball download by fitting a weight distribution hitch

A weight distribution hitch (WDH) is a wonderful device which does exactly what its name implies. Its powerful leveraging effect provides a better distribution of weight across all axles resulting in a level ride height for tow vehicle and trailer, which is particularly important in maintaining effective steering and front wheel braking in the tow vehicle.

However, just because a WDH’s leveraging effect (often compared to raising the long handles of a wheelbarrow) allows this ride levelling to occur, the amount of weight on the tow-ball prior to fitting the WDH does not change. 

4 - Fitting stiffer rear springs to your tow vehicle has the same effect as a WDH

The message about fitting uprated rear suspension on vehicles gets confused between GVM (gross vehicle mass) and GCM (gross combined mass) by some well-meaning owners. Numerous aftermarket suspension companies offer well-engineered upgrades which can increase a vehicle’s payload capacity, and therefore its GVM. Stiffer rear suspension can also reduce rear-end squat under a towing load, but the most effective way to eliminate the nose-lifting ‘effect’ of a heavy trailer on a tow vehicle is with a quality WDH.

5 - You can safely tow at the posted speed limit

A tow vehicle and its trailer are inherently unstable and have a lot of inertia behind them, which always wants to follow the path of least resistance by travelling in a straight line. So if you need to suddenly swerve or there’s a corner approaching, your rig is not too keen on changing direction.

And if you need to stop in a hurry, it also takes much longer to pull up than a non-trailered vehicle. So it stands to reason that the faster you travel with this lot, the greater the risk of losing control, and the bigger the accident. So check if your vehicle’s owner’s manual has recommended peak towing speeds (some do). And from our experience, it’s a good idea to drive slightly below any posted speed limit to provide an extra safety margin should you need to react quickly.

6 - You should accelerate to correct trailer sway

We’re yet to see any electronic trailer sway control system that accelerates a trailer out of trouble! The higher the speeds the more unstable the whole rig becomes. If you do suffer some serious trailer sway and you don’t have a mechanical trailer sway device on your WDH, or the latest electronic assistance, you need to gently ease off the accelerator to avoid any sudden forward weight transfer and then gradually start applying enough brake pressure (with properly adjusted trailer brakes if you have them) to slowly bring it all under control. Once your pulse rate returns to normal, you should also determine what caused the sway in the first place to avoid it happening again.

7 - You should replace your trailer tyres only when the tread depth reaches 1.5mm

Of equal importance is to know how old they are because tyres that have passed their use-by dates can suffer potentially catastrophic failures, particularly when under heavy loads. Tyres generally need replacing every five years because over this time they lose their suppleness, anti-ageing and heat-dispersing qualities.

And this deterioration occurs even faster if they don’t get regular use. The extra risk posed by trailers (including caravans, horse floats and boat trailers) is that they can often sit around unused for months and sometimes years, allowing this important safety factor to be easily overlooked. Manufacturing dates are usually displayed on the tyre wall after the letters ‘DOT’ (Department Of Transport) but the date/year codes can differ between brands. This info is usually published online by each tyre maker.

8 - You don’t need trailer brakes if it weighs less than 750kg

Two figures regularly shown by vehicle manufacturers are their towing capacities for trailers with and without brakes. The maximum weight a trailer can weigh before it needs to be fitted with brakes is 750kg, which has created a general perception that any trailer under that threshold doesn’t need brakes. However, if you drive something smaller than a full-size SUV or dual cab ute, you’ll often find that their towing capacities are less than 750kg.

In some cases several hundred kg less, so the absence of trailer brakes in those scenarios could be just as hazardous as a full-size SUV or dual cab ute towing a tonne or more without brakes. Fact is, trailer brakes are a good idea, no matter how big your trailer.


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