What Is Tow Ball Weight And Why It Matters

Image credit: withoutahitch.com.au

Tow ball weights, and tow ball mass (TBM) are terms thrown around among those driving trailers and towing vehicles, but what do they mean? Should you pay attention to the tow capacity of your camper trailer? How do you measure the amount of weight on your tow balls? Can you use household scales, or do you need a specialist tow ball weight scale?

Here’s everything you need to know to ensure safe towing.

What Is a Tow Ball Limit?

The tow ball is the tool that hitches your caravan or trailer to your vehicle. It attaches to the chassis of the towing vehicle and the tow hitch on the trailer. Your tow ball needs to accommodate your loaded caravan’s specific size and weight. 

Putting it simply, tow ball mass is the proportion of trailer weights applied to towing vehicles. It is also known as the tow ball weight, tow ball load, or tow ball download.

Most trailer mass is on wheels when you tow a caravan or camper. However, a small amount of the towing weight passes to the vehicle via the tow bar and ball. Front-heavy axle caravans will have a heavy tow ball weight; a trailer with heavier rear axles will have a low tow ball weight.

You don’t need to know the measurements to the kilogram, but a rough idea of the trailer’s ball weight will ensure your safety and follow caravan towing regulations. You should especially keep an eye on the towing ball mass if you’re near the limits of your max towing capacities. 

Moreover, your caravan towing weights change depending on the trailer load. This includes the tare weight and payload. If you pack differently each time you go camping, check you’re within the recommended tow ball weight.

Why Is the Tow Ball Weight Important?

There are many reasons why the tow ball weight matters—from avoiding nasty accidents to ensuring you are legally towing.

1. Trailer stability: The lighter your TBM, the more caravan sway. The heavier the tow ball weight, the more stable your trailer tow.
2. Vehicle stress: Tow ball weight applies significant pressure on your car. If you hit a dip and it jerks the vehicle and trailer, it will send much higher forces onto the car and risk damaging the chassis and brake controllers.
3. Legalities: There are many towing rules and regulations regarding the maximum tow ball weight, loading capacity, and towing limits. Also, driving an unroadworthy vehicle could invalidate your insurance.

What Is the Minimum Tow Ball Weight?

The recommended tow ball weight in Australia is about 10% of your aggregate trailer mass or a maximum of 350 kilograms—whichever is the lowest. You’ll hear different caravan tow ball recommendations around. But, generally speaking, you should aim for somewhere between 5% and 15% of the trailer’s weight.

The aggregate trailer mass (ATM) is the gross trailer mass carrying the maximum recommended load.

The minimum and maximum caravan ball weight differ in every country. In Europe, for instance, the max tow ball weight should be 5 – 7% of your caravan’s actual weight. Therefore, you should check each country’s maximum and minimum weights if you plan to travel abroad with loaded trailers.

What Is the Tow Ball Weight of a Caravan?

Every caravan’s tow ball weight will differ. There is no exact number for all vehicles and trailers.

Let’s look at an example. 

A caravan with a 2500kg towing weight should have a maximum tow ball of between 7 – 15% of the caravan’s weight (preferably closer to 10%). This works out to between 150 and 375 KG. Therefore, it would be best if you aimed for a tow ball weight of 250 KG. 

However, the maximum weight depends on the vehicle manufacturers’ and trailer designers’ specifications. In addition, the ideal towing weight must fit the vehicle’s limitations and tow bar.

How Is Tow Ball Weight Calculated?

There are many ways to measure tow ball weights. You could take your caravan to professional weighbridges or use a set of bathroom scales. You might buy a specialist set of tow ball weight scales for accurate calculations.

Using Bathroom Scales

You will need:

• Regular bathroom scales
• A brick 
• Two small pipes (around 15-20cm)
• A sturdy piece of wood (around 1-1.5m)

Start by placing the ball scale and brick on level ground with 90cm between them. Place a pipe on each and run the plank of wood across so it looks like a bridge. 

Load up your caravan to its total weight when towing. Lower the jockey wheel on the wooden plank, at around two-thirds of its length away from the scales. Multiply the weight scale by three for an approximate tow ball weight.

Using a Tow Ball Scale

Alternatively, if you use a tow ball scale, you’ll get a better reading of the tow ball weight applied to the vehicle mass. This is because ball weight measurements are much easier to use. The scale uses a heavy base calibrated metal cylinder with an internal spring mechanism to measure the tow ball mass accurately.

Fix your caravan to the scale (just as you attach it to your car to tow the van), and the scale will adjust to give you the ball weight.

Can You Exceed Tow Ball Weight?

As the manufacturer recommends, the combined weights of your tow ball loads should always be less than the towing car’s weight and towbar limits. If you exceed the overall weights, your towing might push down the rear axle loadings. This lifts the front axles and severely compromises towing abilities.

You might struggle to control braking and steering, particularly on rough terrain. Alternatively, low axle weights might cause too much swaying. A weight distribution hitch can help ensure your caravan meets the ideal tow weight.

How Do I Reduce the Tow Ball Weight on My Caravan?

You must adjust how you pack your caravan to increase or reduce the tow ball weight. Most campers have many compact and efficient storage spaces, so you can take everything you need on your road trip. However, you must take care not to overload your trailer. Too much weight, as we’ve seen, could impact your towing safety.

Consider where you store the heavier items. For example, keep water tanks and spare wheels low to the ground. In comparison, lighter travel gear should go at the top for better stability.

Many factors impact the tow ball weight, including axel location, drawbar length, trailer design, and weight distribution. In addition, electric brakes and brake controllers can ease the stress on your vehicle. When you tow a heavy load, you need brake controllers to prevent the trailer from damaging the chassis. Electric brake controllers may help ease the heavy tow ball weight burden.

Do You Know Your Tow Ball Weight?

Understanding tow ball weights will mean you can safely and legally hitch up your trailer for a holiday. To ensure a smoother towing experience, load your boat trailer, caravans, and camper trailers to the correct weight capacities. Consider using electric braking to relieve stress on the vehicle and tow safely. 

Understanding the rules and requirements of towing your trailer is crucial. In Australia, you must have an electric brake system for vehicles with a Gross Trailer Mass over 750kg. Get in touch with our team today to determine whether you need electric brake controls.