Tow Vehicle and Caravan Weight

by Andrew Woodmansey and Collyn Rivers

 

The weight relationship between tow vehicle and caravan is an important one for safe towing.

To avoid the ‘tail wagging the dog’, it is important that the tow vehicle is at least as heavy as the caravan being towed. If it’s not, the tow vehicle is unlikely to be able to control a caravan should it become unstable when impacted by external forces such as a cross wind, heavy cornering, heavy braking or uneven or slippery road surfaces.

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How Much Weight Safety Margin Should I Allow?

There is some debate (and legislation in Germany) on the ideal weight safety margin between tow vehicle and caravan:

• The conventional wisdom is that the tow vehicle must be at least as heavy as the caravan being towed (i.e. a 1-to-1 ratio between tow vehicle and van weight);

• In the UK there is the “85% rule”. This is not legislated, but is a recommendation of the Camping and Caravanning Club of the UK and other UK bodies. This recommendation states that the weight of the loaded caravan should be no more than 85% of the car’s kerb weight. However, according to the Camping and Caravanning Club of the UK, ‘those who are experienced at towing may go up to 100 per cent of the car’s kerbweight, but no-one should tow a caravan that is heavier than the towing limit of the vehicle it’s behind’;

• In Germany, caravans with brakes and hydraulic shock absorbers may not (by legislation) exceed 0.8 times the empty weight of the tow vehicle unless the tow vehicle does not exceed 80 kmph;

• In Australia, there is no legislation on weight safety margins, but the Caravan Council of Australia suggests that ‘for added safety and peace of mind, the laden tow-vehicle should weigh 30% more than the laden caravan/trailer’ (for the non mathematically minded, this is the same as saying that caravan should not exceed about 77% of the laden weight of the tow vehicle);

Note that the above relates to the weight relationship between tow vehicle and caravan. There is always legislation in each country on the maximum weights of tow vehicles, caravans and towing combinations.

From the above you might think that the Caravan Council of Australia is being the most conservative of all these countries in applying a 77% safety margin. But in fact, because the CCA’s recommendations are based on laden weights of the tow vehicle and not the unladen (or kerb) weights, they are in fact the least conservative.

This can be seen from the following table, which translates these guidelines or regulations into actual weights for eight of Australia’s most popular tow vehicles:

Comparison of Tow Vehicle & Caravan Weight Relationships

 

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UK – Recommendations of the Camping and Caravanning Club of the UK (relates to tow vehicle kerb weight)
Germany – Federal Legislation for caravans with brakes and shock absorbers (relates to tow vehicle kerb weight)
Australia – Recommendations of the Caravan Council of Australia (relates to tow vehicle GVM)
Kerb Weight – the unladen weight of the tow vehicle without occupants or payload
GVM (Gross Vehicle Mass) – the maximum permissible laden mass of the tow vehicle including occupants and any weight applied to the towball
ATM (Aggregate Trailer Mass) – The maximum allowable laden weight of the caravan as assessed by the manufacturer

What is noteworthy from this table is that the recommended (or legislated) maximum caravan weight is significantly lower in all cases than the maximum towing capacities of each tow vehicle (which ranges from 3200 kg to 3500 kg for the vehicles above).

In just the same way as tyre manufacturers stipulate maximum speeds for their tyres (sometimes 300 km/h for normal road tyres), maximum towing capacities are mechanically derived maximums, beyond which things start to fall apart. They are not intended to be fully exploited by the typical user, and especially not the novice user.

So don’t treat the maximum towing capacity of your tow vehicle like an airline luggage allowance (‘it’s there to be used’). Treat it instead as the extreme limit of your towing universe, and stay well within its boundaries.

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So Which Caravans Can I Safely Tow?

Australian manufacturers build some of the heaviest caravans in the world. The reasons for this have generally been linked to poor Australian road conditions which have historically required robust caravan construction methods and materials. This tradition of heavily built caravans is putting the Australian caravan market on a collision course with ever lighter tow vehicles, a subject that will be explored in a later article.

To illustrate this, let’s look at a list of 12 ‘Best Offroad Caravans’ in the Australian market just published by Caravan World magazine. Here they are in order of their Aggregate Trailer Mass (ATM, or maximum permitted weight including payload) and Tare (the mass of the van as it leaves the manufacturer without a payload):

Caravan World magazine’s 12 Best “Offroad” Caravans (April 2014)

                                                                                                      Tare (kg)            ATM (kg)
SLR 1900 Premium Offroad                                                    2740                  4100
Kedron Top Ender                                                                      2820                 3500
Sunland Blue Heeler                                                                 2496                  3500
Otron Signature Series 3                                                         2960                  3490
Lotus Trooper                                                                             2800                  3490
New Age Commando 20 Series                                              2980                 3480
Roadstar Safari Tamer                                                              2820                  3420
On The Move Grenade                                                               2640                 3240
Trakmaster Kimberley Platinum 15.6 (poptop)                 1960                 2700
Retreat Hamilton Offroad                                                       2077                  2500
Goldstream RV 16.6 FKST Panther (poptop)                       1995                  2395
Bushtracker 14ft (poptop)                                                      1820                  2300

Comparing this table to the one further up, do you notice anything interesting? Here are a few observations:

Nine out of the twelve caravans above are too heavy to tow by any vehicle in the list if CCA recommendations are followed;
• There is only one tow vehicle (Nissan Patrol) capable of towing all the caravans in this list (at maximum ATM and assuming the SLR is towed well within its ATM) using the ‘1 to 1’ rule, whilst even the Toyota Landcruiser can only tow nine out of these 12 vans using the same rule;
• Only one of these caravans (a pop top) would be capable of being towed by the Nissan or Toyota if UK recommendations were followed;
None of the above caravans could be legally towed in Germany because there is no tow vehicle (except perhaps a large US 4WD or two) with a sufficient kerb weight to tow these caravans at the stipulated 0.8:1 safety margin

It is fair and reasonable to assert that Australian road conditions are different from those in Europe and that apples should not be compared to oranges. But at the same time, Australian road hazards such as corrugations, animals on the road, dirt tracks and road trains are less common in Europe. It might therefore be reasonable to assert that the CCA is being generous rather than strict in their recommendations.

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 So Who Should I Listen To?

Bearing in mind that the tow vehicles above have some of the largest tow capacities on the market today, you can see the Australian towing dilemma. The typical Australian ‘off road’ tow vehicle and caravan combination now consists of a three ton box pivoting around the overhung hitch of another often less than three ton box, whilst travelling at up to 100 km/h. A potent set of physical forces could be unleashed should anything untoward (and often beyond the driver’s control) happen to this combination.

The UK’s Camping and Caravanning Club states: ‘In perfect driving conditions – i.e. no crosswinds, no uneven surfaces, no air turbulence from lorries and no other hazards, 100% of the towing capability of the car could be applied for all caravanners. However, these road conditions are very rare, so it is wise to be cautious and apply the 85% rule.’

It would be wise for Australian caravanners to follow this advice whilst applying instead the 77% rule that the CCA has carefully considered and developed for Australian caravans and conditions.

And if you are a novice caravanner, it would also be wise to consider investing in a lightweight caravan (i.e. under 2000 kg ATM, which includes most imported European caravans and some shorter Australian ones including pop tops) towed by a suitably heavy tow vehicle until you have developed confidence in your towing skills in a range of road and driving conditions.

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