I'm looking at purchasing a caravan and have pretty much made up my mind on a van with the following weights:
- empty ball mass=132kg
- max ball loading=162kg
I'm confused though on several fronts, the vehicles tow ball weight should be more than 132kg or should it be 162kg at a min?
I've looked at the Sorento however one of your articles suggests that the extra tow pack is no longer available? Thus 100kg is the towball download limit. Could you suggest some other SUVs in the same ball park that could match the towing capacity required? Or should I start looking up a level at the Fortuner/Prado etc...? Your help would be much appreciated. Cheers, Alex
Okay - let's get the basic engineering and the definitions out of the way first. The trailer/boat/caravan has mass. It weighs something, right? Just sitting there, unladen, it weighs 1360kg - that's what tare weight is. And you put stuff in it - water and plates and bedding and whatever the hell else you take with you when you get away from it all. That stuff you put in it has weight, too. And in this case you can put a maximum of 300kg of your stuff in it.
This is confirmed simply by subtracting the tare weight (1360kg) from the Aggregate Trailer Mass (ATM, 1660kg). ATM is the total mass of the trailer with all your stuff loaded into it. This is a limit that you're not allowed to exceed.
Now, a bit of basic physics. A smart, but dead, guy named Isaac Newton, said that action and reaction are equal and opposite. There's an experiment you can do to confirm this. You take your mother-in-law up the top of a 10-storey building and get her to stand on the roof. Your mother-in-law weighs (I dunno) 100kg, or something. So, standing there, her feet are pressing on the roof: all 100kg, straight down, gravity dragging her down onto the roof.
But the bit most people forget is: the roof pushes back. One hundred kilos, straight back, straight up. A balanced force system. 100kg down (weight of mother-in-law); 100kg straight back up (resistance/reaction of the roof). Result: Mother-in-law goes nowhere.
Next: blindfold the mother-in-law, frog-march her to the edge, and convince her to take one small step for mankind. Once she steps over the parapet, the only difference is that the roof is no longer pushing back. Result: She accelerates down to the pavement below. (Result, as they used to say on The Bill.) The quality of your life probably improves, after the speed-bump of the wife's grief.
Same thing happens with the trailer when it's hooked to the vehicle. Instead of the mother-in-law's two dainty feet, the axle(s) and the towball oppose the weight of the trailer by pushing up. Gravity pushes down, the roadway and the towball push up to oppose it - exactly equal and exactly opposite. This can be confirmed because the axles aren't making like the mother-in-law over the edge of Trump Tower. And neither is the tow coupling. (But if aliens were suddenly to teleport to your driveway and vaporise the vehicle, the tow coupling would fall and hit the road - therefore it's pushing down on the towball, and the towball is pushing back ... whenever the vehicle's not vaporised by aliens.)
Unlike the mother-in-law, who has two feet presumably supporting 50kg each, the trailer has two asymmetric feet, and the limit on each one is 1528kg for the axles, and 162kg for the ball. (You'll note that 1528 + 162 = 1690kg: so you can't drive around with both the axles and the ball maxxed out, because the trailer would be overloaded. The limit is 1660kg.)
So, when the trailer is completely empty, the load on the towball is 132kg. When you load it up - and there's some flexibility in how you do this: how much you carry, and where in the caravan you stow this stuff - you're not allowed to exceed 162kg of towball download.
The obvious way to achieve this is to load the van with the maximum gear you plan to carry, and drive to a weighbridge. There, you can weigh the van (off the vehicle) and confirm the total load is under the ATM limit of 1660kg. Then you can hook up the vehicle and drive it onto the weighbridge so only the trailer's axles are on the weighbridge and the vehicle is off the weighbridge. This will measure the weight on the axles only - which needs to be under 1528kg (the trailer's GTM).
If you then take the measured all-up weight of the trailer (the first measurement) and subtract the load supported by the axles (the second measurement) you are left with the towball download, which is the weight the loaded trailer imposes on the vehicle's towball. That needs to be under 162kg.
If it's not, you can try positioning some of the heavier items rearwards. This will lighten the load on the towball. Then take the second measurement again and repeat the process until the ball weight is under the 162kg limit.
See also this exclusive report: Understanding Towing and Load Limits for SUVs >>
THE RIGHT 7 SEATER SUV
It's a great idea not only not to exceed the manufacturer's towing limits in the specifications, but also not to come close to the limits. A 10-20 per cent margin of safety is going to be a conservative, safe operation (in my view). So: if a manufacturer says there's a 2000kg tow capacity limit, maybe it's a good idea to thing about not towing more than (say) 1800kg with that particular vehicle.
HYUNDAI SANTA FE
Tow Capacity: 2000kg
Ball download: 100kg
Verdict: Sorento is a great 7 seater SUV with a superb warranty, a vast standard equipment array and a solid powertrain - but it can't support the trailer's download in this case, and is therefore a scratching.
More on the Kia Sorento >>
Tow Capacity: 2000kg
Ball Download: 100kg
* or 150kg with Genuine Load Assist Kit
Verdict: Santa Fe is practically the Swiss Army knife of 7 seater SUVs. Incredible standard equipment and quality construction, top diesel powtertrain, 5yr warranty, standard full-sized spare tyre, etc.
You'll need to fit the Hyundai Genuine Load Assist Kit (essentially an uprated pair of progressive-rate rear springs). And you'll also need to be careful about how you load the trailer so you don't exceed the vehicle's 150kg towball download limit.
Tow Capacity: 2000kg
Ball Download: 200kg
Verdict: Outlander is an affordable option and - in terms of maximum permitted towball download at least - it's ahead of Santa Fe. But in many other ways it is not. Sure the warranty is 5yrs, but the rest of the vehicle is dated and the equipment level really does not compete.
Outlander is, however, an affordable option, and if it was not possible to conform to the Santa Fe's 150kg download limit (with the kit fitted) then Outlander is an option to consider.
Tow Capacity: 2000kg
Ball Download: 200kg
Verdict: Kluger is expensive but capable, if somewhat bland. There's no diesel engine available (and diesel is a really big asset for towing). The warranty is only three years, the service interval is only six months (the others here: five or seven years, and 12 months for service).
Still, nobody ever got fired for buying a Toyota. The brand certainly leads the market and has its fans. People who love Klugers love Klugers.
Other factors to consider include the amount of towing you plan on doing as a proportion of the driving you'll do. If you're towing a lot - think: grey nomad, trans-Australia adventure - then it pays to buy a vehicle that will treat the trailer as if it's a mere triviality. In this case, a Pajero Sport >> might be a good idea. Click the link for that review, but be aware you'll be trading off a fair bit of refinement if you do - and you have to make a value judgement about whether that's worthwhile of not.
Also bear in mind that diesel engines make ideal towing powerplants (because they deliver a lot more power at low to medium revs). They are also more fuel efficient, but they are generally more expensive to acquire. More on petrol versus diesel >>
If it were me, and I was towing four times a year over moderate to long distances, I'd do it with the Hyundai Santa Fe >> (Elite or Highlander). I'd fit the Genuine Load Assist Kit and carefully ensure the vehicle's 150kg download limit was not exceeded by taking the time to get the placement of the moveable load right as per the description above, using the weighbridge.