How to choose the right new vehicle for heavy towing
Vehicle buyers tend to be vague on this: ‘I want to tow a medium-sized van’ kind of thing. Let’s try a rational, numbers-based approach instead
I get a lot of heavy towing enquiry. Much of it is vague - ‘I wanna tow a medium-sized van’ (whatever that is, in the domain of definition). This enquiry (below) from Steve was a cut above - but he’s still digging a hole for himself. Check it out.
“I am looking at a Kia Sportage Si 2.0L Diesel Automatic, as I have the following ‘toys’: Fishing boat, approx. 1.5t, and camper trailer approx. 1.2t. I also occasionally do a bit of beach driving and light 4-wheel driving (nothing radical) as well as an occasional trip interstate. So, based on that I reckon the Kia will fit my requirements. My only concern is the towing capacity of the Kia @ 1.9 tonnes. Your comments would be appreciated.” - Steve
Let’s divide this problem into two scenarios:
SCENARIO #1: Buying the vehicle; owning the trailer
Two critical weights
You need to know the loaded all-up, fully loaded trailer weight (also known as the ATM, or ‘aggregate trailer mass’ - and sometimes called the GVM of the trailer - ‘gross vehicle mass’ of the trailer). Obviously you need to know this in the heaviest loaded state the trailer is ever going to be used in.
Then you need to know the static towball download the trailer imposes on the vehicle in this most heavily loaded condition. This is basically how hard the trailer presses down on the towball when stationary on a flat, level surface.
Then you need to cross reference these loads against the corresponding load limits (called ‘tow capacity’ and ‘towball download capacity’ in the specifications on the vehicle manufacturers’ websites.
These specs are ‘limits’, meaning they may not be exceeded - even a little bit. There are consequences if you exceed them. Warranty consequences, reliability consequences and (if you crash) potentially legal and insurance consequences. Don’t exceed them.
Proportionality problem - Australian-style
In much of the rest of the world the basic trailer design brief is to impose five percent of the all-up weight on the towball. (For example: 200kg trailer equals 100 kilos on the towball.) However, in Australia 10 per cent is more common. (2000kg / 200kg.)
This leads to a lot of vehicle weight limits falling into the five per cent category. Steve is broadly there, above, with the diesel Sportage’s limits being 1900kg / 100kg.
Broadly, this forces a lot of vehicle buyers in that 2000kg-ish category into a vehicle with grossly more tow capacity than they need, just so they don’t blow the download limit.
And unfortunately, these more hardcore vehicles are often less refined for normal driving (because the severe off-road capability and tow capacity built into the design detracts from on-road refinement).
Hyundai Santa Fe >> (one of my favourit seven-seat SUVs) attempts to bridge this gap with a so-called ‘Genuine Load Assist Kit’ which is essentially an affordable, fully engineered rear spring upgrade that boosts the vehicle’s standard 100-kilo download capacity to 150kg.
It’s not the full 10 per cent - but it is halfway there and increases the towing envelope substantially in Australia.
Measure - don’t guess
Amazingly, many people just wing it here on the numbers, and my strong advice is: Don’t do that.
Head to your nearest public weighbridge (use Google) with the trailer in its most heavily-loaded configuration. The basic process is:
Drive the trailer onto the weighbridge
De-couple, and drive the vehicle off
Weigh the trailer
Reverse the vehicle onto the weighbridge and re-couple the trailer
Inch the vehicle until it is completely off the weighbridge, but the trailer is completely on it
Weigh again (this is the all-up weight of the trailer minus the towball download)
Subtract the lighter weight from the heavier weight to arrive at the towball download
(Alternatively many towbar fitting operations and off-road accessory shops have dedicated towball download scales you can use)
Once you know these loads, you can easily eliminate vehicles that don’t offer the capacities you require.
Conservatism for dummies
Don’t tow too close to the limit. It’s always good to be conservatively under - good for reliability, good for dynamic performance, safer all round.
4X4 utes & 3500kg madness
This is especially true of the 4X4 utes and their 3500-kilo maximum tow capacity.
For starters, it’s ridiculous to tow something that much heavier than the tow vehicle. Ridiculous.
And then there’s the GCM compromise, which elevates ‘ridiculous’ to ‘outright madness’.
‘GCM’ or ‘gross combination mass is another limit imposed on some vehicles for towing. It’s basically the all-up weight of the trailer and all the load in it, plus the vehicle and all the load in it.
Here’s an example: The Ford Ranger Wildtrak has:
3500kg tow capacity
Kerb weight of 2290kg
Can you see the problem here?
Well, if you hitch a 3500kg trailer to the bare vehicle (2290kg) you’re already at 5790kg, leaving you just 210 kilos of payload.
That’s not very much, in the context of passengers, luggage, bullbar, second spare tyre, jerry cans of diesel - mountain bikes in the back, or whatever.
You can see how impractical this is, right? Hypothetically, two excessively fed western carnivores and a 3500 kilo trailer, and your vehicle will blow the GCM limit.
Transmission types & towing
There’s been an explosion in transmission types: DCTs and CVTs have been added to the mix in addition to conventional autos and of course manuals.
Conventional autos are best for heavy towing. Manuals are OK. I question the durability of CVTs and DCTs for repeated heavy towing near the manufacturer’s limits.
I’m not talking about occasional heavy towing, and certainly not talking about taking a light box trailer and occasional runs to the tip or Bunnings. CVTs and DCTs will withstand that OK - especially if you drive sympathetically.
But if heavy towing is going to be a mainstay of your vehicle’s operation, I’d be looking for a conventional auto.
SCENARIO #2: Buying the trailer afterwards
Basically you apply this process in reverse - you have to choose a trailer that will not blow the vehicle manufacturer’s towing limits - fully loaded.
Here I urge you to shop around, to find a trailer designed closer to five per cent on the towball download, rather than the long-standing 10 per cent, because that’s going to really open up your vehicle options. This process is, in a sense, more challenging.
If you are buying a brand-new trailer from a manufacturer is may be possible to engineer this in, or at least get closer to five per cent, by moving some of the trailer’s internal components - like a water tank or jerry can holders.
Not all towing is equal
I urge you to strive for the lightest trailer you can get away with - it will impose less stress on the vehicle, and you’ll probably get away with a more refined vehicle for the times when you’re not towing. (Because the heavy tow vehicles are all somewhat agricultural in comparison.)
There’s a fundamental difference between these two towing cases:
Towing for three or four weeks of annual holidays and maybe two shorter trips a year, which might be only six days in total spent towing (and 359 days not towing). Also in this category is a fortnightly 30-minute trip to the local boat ramp.
Then there’s the case of becoming van-toting grey nomads, continuously touring Australia for an indeterminate period of time.
In the first case I’d advocate getting a vehicle that’s better for normal non-towing duties (normal on-road driving) but which will also town the trailer safely.
In the second case I’d recommend getting a vehicle with plenty of hardcore tow capacity built in, in reserve.
This is just sensible tweaking of the choice to get a vehicle most suited to what it will ultimately be doing, most of the time.
I’d suggest that the missing component in the discussion so far is you - the driver.
Heavy towing is specialised and demanding - so it’s unreasonable to expect yourself to jump out of mum’s Camry and into a Ford Ranger Wildtrak hitched up to a 3.5-tonne rolling bordello and seamlessly adapt to those demands.
It’s actually amazing that no additional training is required.
At the very least, adapting to heavy towing means driving ultra-conservatively, leaving big safety margins (in cornering speed and stopping distance).
And finally, I advise you to use your rear-view mirror.
Use it a lot.
If you’re holding up the world, you’re doing this wrong. Pull over, diplomatically and often, the better to let the rest of the world drive past you at its default highway pace.
There’s really no need to be an inconsiderate bastard. Humanity is already all stocked up in this respect.