How to prevent an overweight caravan

In days gone by the only mass people worried about happened on Sundays. These days, if you’re towing and don’t kneel down and pay homage at the shrine of mass legalities, you’ll risk paying for your sins with a fine or worse a crash -- and no insurance payout.

You have to know what your rig is legally allowed to weigh and ensure that it doesn’t weigh any more.

If you read the towing section of almost any passenger vehicle’s operating guide, it’ll say something like this: “Your vehicle is designed primarily as a passenger carrying vehicle. Towing any type of trailer will affect the vehicle’s handling, performance, braking, durability and fuel consumption.”

The designers and engineers didn’t get a brief saying: “Management wants a vehicle that’ll tow a dirty big caravan, horse float or boat trailer, and if it happens to fit some people and their luggage inside too, that’s great.”

Load-bearing components like axles, suspension, tyres and the rear frame or chassis section where the towbar bolts up, are not designed to carry heavy loads, first and foremost. Neither is the vehicle’s powertrain designed to tow 3500kg up steep inclines at full throttle in 40 degree heat all day…

Also read: Overweight utes threaten road safety

Someone forgot to tell that to the marketing department; no, these vehicles won’t lug the family and their luggage as well as tow a commercial airliner at the same time, despite what the advert said and showed... before it got to the small print no-one looks at.

Don’t believe the hype!

Some of these vehicles cannot tow what the makers claim they will, if the vehicle itself is loaded with anything approaching a realistic weight - that is, their Gross Combined Mass (the weight of both the tow vehicle and trailer combined) is too high.

Then there are those that come under the rated GCM and when not towing anything are fine with their GVM (Gross Vehicle Mass), but when a trailer is plopped onto the towball, the extra payload mass pushes them over GVM.

How do you know if your rig is overweight? Take it to a weighbridge and get two weights: the first with just the vehicle on the pad (with the trailer still hitched but not being weighed), which will allow you to see if you have exceeded GVM. Then put both the vehicle and trailer on the weighbridge pad, which will give your rig’s weight in relation to GCM.

Also read: The truth about 3500kg tow ratings

A side benefit of this weigh-in is that you’ll be able to get the trailer’s axle weight (by subtracting GVM from GCM) so you can check that you’re not over the van’s Gross Trailer Mass (GTM) limit.

Does it measure up?

We’ve listed a number of towing wagons and utes below to show how easy it is to exceed maximum permitted mass figures. It’s only meant to be a general guide but underlines the importance of measuring your rig’s actual weights.

The only way to put at rest any argument about what your rig weighs is to go and measure it. It’s too risky to guess.

In the notes below, you’ll see the kinds of items we’ve included as payload. Sure, your weights are probably different -- you might only have two people riding in your medium ute, not four -- but you might also have a slab of beer, an off-road recovery kit and a gennie in the ute tray, which we haven’t included.

Note that we haven’t double-dipped with our figures; we’ve included towball mass in out GVM figures, yes, but accordingly subtracted towball mass from trailer weight for GCM calculations.

So if it’s a 3500kg trailer being towed (as in our examples for medium and large utes and large wagons), we’ve allowed 10 per cent as towball mass (350kg, which becomes part of payload) and 3150kg as the remaining weight on its wheels (Gross Trailer Mass).

Also read: The truth about overweight caravans

So in the case of the Ford Ranger towing a 3500kg trailer, for example, we’ve got kerb weight of 2159kg, plus 864kg payload (adding up to 3023kg, 177kg less than GVM) plus 3150kg trailer mass (because we’ve already counted the 350kg TBM in payload) for a total of 6173kg (173kg more than the rated GCM).

While medium wagons and large (American) utes only represent a small section of the towing market, their towing capacities are the most realistic. The worry is that the bigger-selling medium ‘one-tonne’ ute and large wagon segments are populated by models that can’t tow what their manufacturers claim they can, while also towing at their maximum capacity.

Real-world examples:

Medium SUVs

Medium Utes

Large SUVs

Nissan Patrol Y62
Payload: 900kg (2)
Vehicle mass: 3650kg (150kg more than GVM)
Vehicle and trailer combined mass: 6800kg (200kg less than GCM)

Toyota LandCruiser 200 Series
Payload: 900kg (2)
Vehicle mass: 3640kg (290kg more than GVM)
Vehicle and trailer combined mass: 6790kg (60kg less than GCM)

Large Utes

Payload scenarios explained:

(1) Payload: 433kg (Two occupants 160kg; TBM 150kg; Towbar and EBC 35kg; Nudge bar and driving lights 25kg; 50L portable car fridge (filled with provisions) 30kg; cargo barrier 16kg; UHF radio and antenna 10kg; towing mirrors 5kg; fire extinguisher 2kg).

(2) Payload: 900kg (Four occupants 250kg; TBM 350kg; Bullbar and driving lights  60kg; roof racks, tray and luggage 60kg; Towbar and EBC 35kg; 5 x off-road tyres - additional weight over H/T tyres 35kg; 50L portable car fridge - filled with provisions 30kg; Weight Distribution Hitch 25kg; 1 x jerry of fuel 22kg; cargo barrier 16kg; UHF radio and antenna 10kg; towing mirrors 5kg; fire extinguisher 2kg).

(3) Payload: 864kg (Four occupants 250kg; TBM 350kg; bullbar and driving lights  60kg; ute hard lid 40kg; towbar and EBC 35kg; 5 x off-road tyres - additional weight over H/T tyres 35kg; 50L portable car fridge - filled with provisions 30kg; weight distribution hitch 25kg; 1 x jerry of fuel 22kg; UHF radio and antenna 10kg; towing mirrors 5kg; fire extinguisher 2kg).

(4) Payload: 834kg (Four occupants 250kg; TBM 320kg; bullbar and driving lights  60kg; ute hard lid 40kg; towbar and EBC 35kg; 5 x off-road tyres - additional weight over H/T tyres 35kg; 50L portable car fridge - filled with provisions 30kg; weight distribution hitch 25kg; 1 x jerry of fuel 22kg; UHF radio and antenna 10kg; towing mirrors 5kg; fire extinguisher 2kg).