Your questions answered: what is down ball weight?

In this edition of Your Questions Answered, Robbo offers some advice on how to manage tow ball weights when towing a caravan and unpacks which plug-in hybrid offers the best vehicle-to-load solution.

Got an automotive question but you don’t know where to find the information you need? Never fear, email us here at editor@carsales.com.au

Question: We are starting to think about buying a small caravan for family holidays, but I’m a bit worried about all the facts and figures around towing weights etc.

One I’ve never heard of is ‘down ball weight’. We plan to use our trusty Isuzu MU-X to tow with. Will down ball weight be an issue? – Phil

Answer: Hey Phil, there is a lot of data involved when it comes to figuring out what works – and what doesn’t – when it comes to towing. Luckily, the carsales team has just updated its terrific piece on towing weights which explains it much better than I can.

In short, down ball weight (sometimes known as tow ball weight) is how much weight is pushing downwards on your car’s tow ball once the trailer is hitched up. Unlike all the other data points, down ball weight is somewhat variable, based on how you’ve loaded the trailer or even what kind of hitch setup you’re using.

Down ball weight is important because it has a direct effect on the stability of trailer and tow car and can also impact how the tow car performs. Imagine placing a huge weight directly on the rear bumper; it will push the rear suspension down and lift the front end up, which reduces the front axle’s ability to grip and steer.

The magic number is 10 per cent of your trailer’s total weight, including everything you’re taking with you (water, food, tools etc.), on the tow ball.

Looking at our recent Kia Tasman tow test as an example, we can adjust our down ball weight of around 165kg (or 10 per cent of our total trailer and load figure) by moving the car backwards or forwards to redistribute the load.

If our car is too far back on the trailer – and we’re only talking 10-15cm – it really reduces the stability of the load and increases the danger of the pendulum effect. This is where the trailer starts to sway and can’t be controlled, acting like the pendulum on a grandfather clock until it tries to overtake the tow car. Not ideal.

Your MU-X is a great tow car in its own right, and I like the fact you’re talking about a small van. Just because your car can tow 3500kg doesn’t mean you should. A properly assessed combo will take into account everything from potential travel distance, number of people and total amount of cargo to sufficient on-board spare tyres and tools, communication gear and water supply.

Good luck with it all.

Question: I’ve just bought myself a new e-mtb, which can travel a surprising distance on a single charge. I’m starting to look at my next car (my current car is a Subaru Outback), and I’m idly wondering if I can use a plug-in hybrid to top up the e-mtb if I go on a road trip? – John

Answer: Hey John, that’s a super interesting question. In short, the answer is yes, as long as you pick the right car. Vehicle to load, or V2L, gives you the flexibility to use the high-voltage battery in your car as an external power source, which can be easily accessed via an adapter that plugs into the car’s charging socket.

A typical e-mtb battery is about 640Wh in size and the included charger is usually single phase and rated at just two amps, so even a moderately sized PHEV battery would easily cope with that. A caveat here that I’m sure you’re across… always use an approved charger for the bike battery.

As to which car to pick, it’s a constantly shifting sea at the moment. Top of mind to replace something like your Suby is the Mitsubishi Outlander PHEV, which runs a 20kWh hour battery and can be set to automatically protect a set amount of charge (so you don’t burn through the entire battery with repeated used of a popcorn maker, for example). It’s also big enough to fit an e-mtb inside. It’s expensive, though.

If you want to go the ute option, the BYD Shark 6, Ford Ranger and GWM Cannon all offer V2L-equipped hybrid versions in the line-up.

However, as a mountain biker myself, I’ve never been convinced that a dual-cab ute is a suitable bike hauler. The tray is too small, security is a concern and, especially with the heavier e-bikes, actually heaving the bike in is a pain.

Got an automotive question but you don’t know where to find the information you need? Never fear, email us here at editor@carsales.com.au

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