MAJOR INVESTIGATION: TOW CAPACITIES EXPOSED

We uncover the lies, deceit and marketing hype underpinning your vehicle’s claimed tow capacity. We get the truth about what you can actually tow

WORDS BY STEVE COLLINS, PHOTOGRAPHY BY CARAVAN & MOTORHOME ON TOUR

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Tow capacities. So many caravanners think that their modern common-rail diesel is rated to tow 3000-3500kg all day every day because, as silly as it sounds, the TV said so. But are manufacturers pulling the wool over your eyes?

The fact is, you could be driving an illegal rig and putting yourself, your passengers and other road users at risk without even knowing it.

The driver, the passengers, the vehicle, the tow bar, the trailer and your cargo all affect how much you can legally tow. Any one of these factors would drastically tip the scales out of your favour, leaving you legally liable in the event something does do wrong.

Is your fancy new ‘3500kg’ tow vehicle, actually able to tow 3500kg when you’re loaded for a trip? Well, this issue we’re going to delve into the nuts and bolts of real-world tow vehicle capacities. We’ll show you the two reasons why you can’t tow as much as you think, plus, the real toll it’ll take on your vehicle, if you do.

So grab your vehicle’s specification manual from the glove box and pull up a camp chair; because you’re not going to want to miss this.

THE INSIDERS

We’re not just expecting you to take our word for it, either. This is why we’ve got three industry insiders who are exposing the industry’s best kept secrets.

JOHN EGGENHUIZEN

GETABOUT TRAINING SERVICES & TOW-ED

If there’s one person who knows safe tow practices, it’s Getabout Training Services and Tow-Ed Operations Manager and instructor, John Eggenhuizen. John’s been a towing 4WD and first aid instructor for decades, which is why we couldn’t pass up the opportunity to get him involved in the investigation.

ANDREW LEIMROTH

BERRIMA DIESEL

Andrew boasts 66 years of combined industry experience he shares with his father, Reinhard Leimroth. The man behind DP Chip; Andrew specialises in all aspects of diesel fuel injection.

JUSTIN MALAPONTE

NQ CRASH & 4WD SPARES

As Managing Director of NQ Crash & 4WD Spares in Cairns, you can bet Justin’s seen the good, bad and ugly when it comes to towing in the top end. Over the years, tow vehicles have poured into Justin’s workshop, having come to grief while travelling in the remote north. So when it comes to pushing tow vehicles to their limits, you can bet Justin’s just about seen it all.

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TOW CAPACITIES EXPLAINED

Two words… “up” and “to”. ‘Up to 3500kg towing’, and admittedly a small oversight that a lot of us make, means not only can’t you legally or safely tow what you think you can, but you might even have to shed some serious kilos out of the van and tow rig before you set off for camp next.

In the eyes of the law, the onus is on us to ensure we’re doing the right thing. And sadly, the devil in the detail of this scenario is often buried so deep in the fine print, or a 300 odd page vehicle manual, that most of us don’t even realise it’s there.

GLOSSARY OF TERMS

KERB WEIGHT

This is the unladen mass of a vehicle in standard form, including fluids like fuel and coolant, with no payload or added accessories.

GROSS VEHICLE MASS (GVM)

This is the maximum total mass the vehicle can weigh once fully loaded.

BRAKED TOW RATING

The total mass of any trailer, with trailer brakes fitted, the vehicle can tow. Any trailer over 750kg requires brakes, and any over 2000kg must have brakes on all wheels and include an automatic break-away system.

AGGREGATE TRAILER MASS (ATM)

ATM is the total mass of the trailer when carrying the maximum load recommended by the manufacturer. This includes mass imposed onto the towing vehicle when the combination vehicle is resting on a horizontal supporting plane.

TOW BALL MASS

This is the mass exerted on the tow ball by the fully loaded trailer. A side note for later - when your caravan is hitched up, this mass is included toward your tow vehicle’s payload.

PAYLOAD

Your payload is GVM - Kerb (Tare) Weight and Tow Ball Mass. To think of this in a more practical way, it’s the difference between standard and maximum weights and include things like your luggage, camping gear and extra passengers.

TRAILER TARE MASS

This is the total mass of an unladen trailer when ready for service, and with all fluid reservoirs (except water and waste water tanks in caravans) filled to nominal capacity (except for fuel, which should be 10L only), and with all standard equipment and any options fitted. This includes mass imposed onto the towing vehicle when the combination vehicle is resting on a horizontal supporting plane.

GROSS COMBINED MASS (GCM)

GVM + ATM = GCM. This is the maximum gross combined mass of the trailer and the maximum allowable mass of the vehicle. This is the most overlooked and most influential statistic of them all. Read on to find out why…

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RULES & REGULATIONS

Now we understand the difference between all of these terms, let’s hand over to the officials to see where they stand.

According to the NSW Roads & Maritime;

“The loaded mass of the trailer must not exceed the LESSER of;

“The rated capacity of the tow bar and tow coupling.”

“Maximum towing capacity of the vehicle.”

“Maximum carrying capacity of the trailer.”

“Maximum rated carrying capacity of the tyres.”

So, whichever of the above four specifications are the lowest - that’s your real towing capacity. But that’s not the end of it. No, no. You’ve still got to do the math to figure out what these figures actually are taking into account. Things like your luggage, passengers and aftermarket accessories.

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SO YOU THINK YOU CAN TOW 3500KG - THINK AGAIN!

Right, let’s do some maths. For argument’s sake your van weighs in with an ATM of 3500kg, a Tare of 2900kg and a conservative ball weight of 250kg.

You opt for a modern fuel efficient dual cab ute, because let’s face it; the TV said it can tow up to 3500kg and they’re reasonably well priced, right?

Using an automatic 4×4 2016 PX MkII Ford Ranger XLT as an example, we’ve mapped out a few scenarios to give you a good understanding of what you can and can’t tow in the real world.

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VEHICLES THAT CAN TOW 3.5T

AUDI Q7

Ford PX Ranger

Holden Colorado

Isuzu D-MAX

Jeep Grand Cherokee 3.0TD

Land Rover Discovery 4

Land Rover 90

Mazda BT50

Nissan NP300 Navara

Nissan R51 Pathfinder (ST-X550)

Nissan Patrol V8 Ti and Ti-L

Toyota HiLux (2016)

Toyota LandCruiser 70/76/79 & 200 Series

VW Touareg

WHAT SIZE VAN CAN I TOW IF MY TOW VEHICLE IS EMPTY?

Gross Combined Mass (GCM)

6000kg

Kerb Weight

2247kg

Tow Ball Mass

250kg

Maximum caravan ATM

3503kg

WHAT SIZE VAN CAN I TOW IF MY TOW VEHICLE IS HALF FULL?

Gross Combined Mass (GCM)

6000kg

Kerb Weight + 50% of rated vehicle Payload

2723kg

Tow Ball Mass

250kg

Maximum caravan ATM

3027kg

WHAT SIZE VAN CAN I TOW IF MY TOW VEHICLE IS AT IT’S GVM?

Gross Combined Mass (GCM)

6000kg

Gross Vehicle Mass (GVM) (including Tow Ball Mass)

3200kg

Maximum caravan ATM

2800kg

And your vehicle Payload capped at

703kg

Here’s where manufacturers get you on technicalities. Yes, technically, you could tow ‘up to 3500kg’ - If, and only if your tow vehicle is empty.

Doing any sums like this, you really need to work backwards from your Gross Combined Mass, because this is the maximum figure your hitched up tow rig is allowed to weigh, no matter where the weight is. Naturally that means, if your tow vehicle weighs more, your van has to weigh less to stay within safe limits, and vice versa.

Let’s say you work out that half of your vehicles’ suggested Payload is about 476kg so you go ahead and fit a bullbar, drawers to store your tools and spares, a fridge on top of that, a 20L jerry can of emergency water, a second battery to run the fridge and roof racks to carry your kayak. All up, you’d be adding about 310kg (at least). That leaves 160 odd kilos for your passengers, the dog, extra fuel and souvenirs. Pretty realistic for a lot of us, but now you’re restricted to towing a van that weighs no more than 3027kg.

travelling and you’re used to carrying more of your gear in the vehicle, or maybe you’ve got a few kids so the car is packed to the hilt, and now you’re looking to upgrade and you need to figure out how much you can legally tow.

First, you’re going to have to shave some weight because you need to allow 200kg for the tow ball weight. But that’s okay, because you can transfer a lot of your gear to your caravan. The thing is, with your vehicle at GVM, you can now only tow a 2800kg van.

HOW MUCH CAN I CARRY IN THE TOW VEHICLE?

Your van has an ATM of -

3500kg

3000kg

2500kg

Gross Combined Mass (GCM)

6000kg

6000kg

6000kg

Maximum allowable tow vehicle GVM

2500kg

3000kg

3500kg

Tow Ball Mass

250kg

250kg

250kg

Kerb Weight

2247kg

2247kg

2247kg

Maximum allowable payload in vehicle

3kg

503kg

1003kg

Let’s look at it the other way. You’ve already got a van and you want to find out how much you need to remove from the tow vehicle to return to safe and legal weights.

Starting from your GCM, you’ll need to minus the weight of your van to find the maximum allowable weight of your tow vehicle. From this figure you’ll need to minus tow ball mass, and the weight of the empty vehicle. What’s left is the Payload you can add to your empty tow rig. And don’t forget, passengers are included as payload. Better cut back on those cheese and bickies, eh?

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WHAT IS A SAFE VEHICLE/CARAVAN WEIGHT RATIO?

JOHN EGGENHUIZEN GETABOUT TRAINING SERVICES & TOW-ED

“I believe that the best rule of thumb is the 85% rule. That is to purchase a caravan which has an ATM which is no more than 85% of the towing capacity of the vehicle. This gives the vehicle a bit of breathing space, which will in return give you better fuel economy and a safer travel experience.

If the vehicle is right on the limit, then it is always working harder than it needs to, which means that you as the driver are having to keep it in the sweet spot to best utilise the available torque, which in turn means you are having to work harder than you need to. I thought the whole idea of going on holidays was to relax, and you can’t do that if you are constantly worrying about how the vehicle is coping with the van. By not towing at vehicle capacity it gives you the opportunity to relax and actually enjoy your holiday.”

THE COST OF TOWING AT MAXIMUM CAPACITY

Yeah okay, you’ve moved a few things around, ditched your third set of dinner plates and scraped in underweight in all areas of concern, so technically, you can ‘legally’ drive on the road. But is your tow rig actually ‘safe’ to drive? And what toll will towing at maximum capacity have on the vehicle’s longevity?

CONSIDERATIONS IF YOU’RE THINKING ABOUT UPGRADING

JOHN EGGENHUIZEN GETABOUT TRAINING SERVICES & TOW-ED

1 Don’t confuse want and need. Buying a van that suits your needs rather than your wants, you will generally end up with a van that is smaller and easier to tow.

2 Has the tow vehicle got Trailer Stability Assist? This is a system that comes with the vehicle, is transparent to the driver, is always on and cuts in when the vehicle senses that the trailer is swaying. I would not own a tow vehicle that doesn’t have Trailer Stability Assist. It will help to keep you safe if things go wrong.

3 Learn what the different caravan and vehicle weight tolerances are, and how they apply to you and your vehicle. ATM, GTM, TARE, CGM, GVM, and maximum axle loads are all extremely important. Without this knowledge, you are towing blind. I’m sorry, but ignorance is no excuse, and if you knowingly exceed these limits, then you are simply dangerous and stupid.

4 What is your existing skill level? Are you able to tow and more importantly, manoeuvre that van into the areas you wish to go? A smaller van may be easier to manoeuvre.

5 Cost; if you buy that huge caravan, then you may have the cost of having to upgrade your vehicle to something that is more suitable to tow it. Can you afford to do that, or is that decision going to eat into your hard earned travel savings?

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SMALL ENGINES TOWING BIG VANS

ANDREW LEIMROTH BERRIMA DIESEL

“Advancements in technology means smaller engines are now producing more power. Getting more air into a diesel means you can add more fuel which is how more power is made. Obviously the larger capacity engine is running at far less of its full potential compared to a smaller engine, so the larger capacity engine that is doing it easy will most likely last longer. That said, if a smaller high tech engine is serviced more regularly than the long service intervals some manufacturers suggest, it can still last a long time.”

CAN I TOW 3500KG ALL DAY, EVERY DAY?

JUSTIN MALAPONTE NQ CRASH & 4WD SPARES

“Most vehicles are not capable of towing 3-3.5 tonnes all day every day. Unless you have deep pockets and shell out heaps on one of those big American tow vehicles, the simple answer is no, you should not be towing these weights.”

ARE YOU TOWING BEYOND YOUR LIMITS?

JOHN EGGENHUIZEN GETABOUT TRAINING SERVICES & TOW-ED

“In my position as the owner of Tow- Ed, I have forged great relationships with a number of insurance companies. The information that I am getting at the moment indicates that the accident rate involving caravans is increasing, rapidly. There are more caravans out there than ever before, and people are towing bigger rigs than ever before. Unfortunately, there are often cases where a driver’s ability does not match their ambitions, which results in a ruined holiday at the very least, or worst case, the loss of a loved one.”

HOW TOWING AFFECTS YOUR ENGINE’S LONGEVITY

ANDREW LEIMROTH BERRIMA DIESEL

“Running any engine at its maximum must have some effect on wear and tear. If we look at an older 4.2L mechanically injected turbo diesel under its maximum power and said it was running at 60% of its actual duty cycle (ability), then we would probably have to say a typical newer smaller 2.5L common-rail diesel (which produces more power than its older, bigger brother) under its maximum power could be running at a higher actual duty cycle (ability) of maybe 80 or 90%. Running the smaller engine at its maximum power will probably mean it will not last as long as its larger brother, which by its design era, is less stressed and larger in capacity.”

TIPS FOR TOWING BIG VANS

DRIVELINE DURABILITY

JUSTIN MALAPONTE NQ CRASH & 4WD SPARES

“Once you add an extra 3T behind any standard vehicle, things start loading up. The standard clutch is certainly not designed to withstand pulling these weights constantly. Unless you have upgraded the automatic with a larger oil cooler and a heavy-duty valve body, it’s also going to fail eventually, as a result of the extra load and heat the gearbox has to deal with, will wear the clutch packs out.”

SUSPENSION AND STEERING

JUSTIN MALAPONTE NQ CRASH & 4WD SPARES

To tow safely, you need to have your van and vehicle level or you could quite possibly cause an accident. Vehicle manufacturers have to ride the fine line between comfort and load carrying ability when they sell a vehicle, and in order to maintain comfort, they need to provide a softer ride.

When you hitch up your 3500kg van, even though it can technically tow it, the suspension is still likely to sag, so you’ll possibly need to upgrade your rear suspension to handle the extra weight. Also, because the tow vehicle is carrying the extra load over the rear of the diff you will notice that the steering will be lighter, because weight is being shifted from the front to the rear. This can result in noticeable understeer in adverse conditions.”

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ARE YOU AT RISK OF BENDING YOUR CHASSIS?

JUSTIN MALAPONTE NQ CRASH & 4WD SPARES

“Bending a chassis is pretty hard to do, but it’s not impossible. If you are using air bags in the rear of your tow vehicle, don’t be tempted to overinflate them or carry more than your rated capacity.

Air bags are there to level the vehicle, not to act as stabilisers. If you do over-inflate and overload your rear end, you are likely to bend the chassis as too much weight is being supported by parts of the chassis that aren’t designed to carry weight.

To help prevent this, I would upgrade the springs or leaf packs so the air bags are not required to do as much work.”

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AUTOMATICS VS. MANUALS

Generally speaking, autos are easier to drive and will get heavier vans off the line while placing less strain on driveline components. Autos protect your driveline from stop/start shock loads often encountered when towing a van in traffic, thanks to the slipping action of the fluid drive coupling (the torque converter) autos utilise.

Where manuals excel, though, is at high speed cruise. While constantly thumping through gears in a manual increases wear and tear on your clutch, syncros, gears, and differentials - once you’re up to speed and cruising, they are usually more fuel efficient because you have direct drive from your engine to your driveline. The other benefit is that manuals don’t get as hot as autos, so if you’re towing up a long steep hit in the middle of summer, a manual is less likely to overheat.

BRAKES

JUSTIN MALAPONTE NQ CRASH & 4WD SPARES

“If your tow rig weighs a combined 5t (say 2.5t vehicle + 2.5t caravan), the poor standard brakes are under the stress of trying to pull up twice their unladen weight. Yes, it is assisted by the van’s brakes, and yes it will stop, but prolonged braking can cause the pads, rotors, shoes and drums to overheat, or worse, boil the fluid in the lines, which results in a potentially dangerous brake pedal that sinks to the floor.

If you tow continually I cannot recommend a brake upgrade enough. Heavy-duty pads, and if you have discs all round then a set of upgraded slotted/vented rotors, will keep the rotors cooler longer under heavy braking.”

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WHAT UPGRADES ARE AVAILABLE?

GVM UPGRADES

Approved GVM upgrade kits are available for a range of makes and models, and usually involve upgrading the brakes and suspension, and in some cases reinforcing the chassis, at a minimum. GVM upgrade kits can only be fitted by an authorised (DOTAR certified) facility, and the kit needs to be federally approved, or at a minimum, approved for road use in your state.

Unfortunately, a GVM upgrade does not automatically mean your GCM or tow capacity increases with it. You can do your own sums based of our calculators above to help you juggle weights, but a GVM upgrade will only give you more flexibility in where you distribute the weight.

Some manufacturers offer GVM upgrades from factory, whereby they upgrade the suspension, brakes and tow bar, before stamping the vehicle with a higher GVM as it rolls along the production line. What’s involved and what it costs varies for every make and model, and unfortunately, it’s not available for all vehicles. The good news is; approved GVM upgrades won’t void your warranty.

SUSPENSION UPGRADES

Matching a set of springs and shock absorbers with a constant load rating the same as the combined weight of your payload plus ball weight will help to support the loads placed of your rear axle.

If your vehicle has leaf springs in the rear (like most modern dual cab utes), you have the option of installing an additional load helper leaf to your existing leaf pack. These helper leaves only come into play when load is applied, and don’t affect ride comfort for normal driving.

You can also fit helper airbags to your rear suspension, which can be inflated to support the additional weight of your trailer, and then deflated for normal driving. When considering airbags, it’s important to remember that some types of airbags can place additional stress on parts of the chassis that were never designed to bear any significant loads (more-so in leaf-sprung vehicles). The use of airbags does not allow you to tow over the specified towing capacity of the vehicle or exceed your vehicle’s GVM.

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WEIGHT DISTRIBUTION SYSTEMS

John Eggenhuizen - Getabout Training Services & Tow-Ed

“Probably the best modification that anyone can make, is to fit a good weight distribution system (WDS). There are several on the market. Also very important that you learn how to set them up for yourself. Don’t rely wholly on your dealer to do this for you. As a good caravanner, you should be up to speed on how to set up your WDS.”

CAN I UPGRADE MY TOW CAPACITY?

Due to strict ADR rules these days, it’s becoming extremely hard to re-engineer a vehicle to accommodate an increased tow capacity. Engineers would need to assess the power to weight ratio, the vehicle’s pulling power, weight distribution, brakes, suspension, chassis design, axle load and strength of design in a crash situation. In most cases you’ll find it’s just not feasible.

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SETTING OFF INTO THE SUNSET

If you’ve just laid down a deposit on a new tow rig, don’t be too concerned. You haven’t bought a lemon. Just take the time to read the service manual, check the specs and weigh your van. Grab your calculator and work out what you can and can’t safely tow, and shift payloads around to ensure you have a safe, underweight and well balanced load. If you are a little on the heavy side, this will usually remedy the situation.

Truth is, modern tow vehicles are built stronger than ever before, and those vanners who do run into strife do so because they turn a blind eye to the scales. Don’t become a statistic. If you cut down on unnecessary weight, invest in a quality weight distribution hitch, maintain your tow rig and drive to the conditions, you’ll be on track to many years of trouble-free touring.

TOP TIPS FOR IMPROVED ENGINE RELIABILITY

ANDREW LEIMROTHBERRIMA DIESEL

“Probably the best thing you can do when you think the engine is under sustained load, in other words you are probably an inch or so further down on the throttle than normal, is to change down a gear. When you do so you will notice that, while the engine is revving slightly higher, your foot has also come off the throttle a bit which in turn is definitely reducing engine load.”

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