The Importance of Tow Ball Mass: A Guide to Safe Towing

Towing a trailer or caravan can be a great way to enjoy the great outdoors and travel with all the comforts of home. However, it is important to ensure that your towing rig is safe and compliant with the applicable laws and regulations. One of the important factors to consider when towing is ensuring you have the correct Tow Ball Mass (TBM).

The TBM is the weight that is exerted on the tow vehicle by the caravan/trailer through the tow ball. This weight is determined by the weight of the caravan/trailer towed, plus any additional cargo loaded into the caravan/trailer (water, food, chairs, BBQ, etc..). It is important to have the correct TBM because if it is too heavy, it can negatively affect your vehicle’s ability to steer and brake effectively, it can also cause damage to the tow vehicle. Additionally, if the tow ball mass is too light, it can cause the trailer or caravan to sway and become unstable, creating a very dangerous situation for both yourself and other road users.

So, what is the correct TBM you ask? As a rule of thumb, your tow ball mass should weigh around 10% of your caravan/trailer’s actual Aggregate Trailer Mass (ATM). Here at OVERLOADED we like to see a customer’s tow ball mass between 9-11%

There are a couple of ways to determine your current tow ball mass:

1.     Using a tow ball scale.

2.     Calculate the difference between your vehicles actual gross vehicle mass (GVM) both with and without your caravan attached, resulting in what can safely be assumed the down force (tow ball mass) being transferred to your vehicle.

3.     Weighing your Caravan and/or trailer at the jockey wheel at a weigh bridge. THIS IS NOT RECOMMENDED as the measurement is taken at the incorrect location on the draw bar and will significantly skew your results.

BEWARE OF CHEAP TOW BALL SCALES!!! They are not all created equal. In our experience we have found a lot of these scales to be inaccurate. A major downfall of most of these scales is that they are not height adjustable. Weighing the tow ball at the incorrect height will significantly skew your results. Weighing the tow ball at a lower height than where it sits on the tow vehicle will apply more downwards force onto the scale. Weighing the tow ball at a higher height will move the down force to the back of the caravan/trailer giving the reading that tow ball is lighter than it is. The tow ball weight must be taken at the same height as when it is connected to the tow vehicle.  

Here at OVERLOADED we utilise a built for purpose adjustable height tow ball scale, which is calibrated annually (at a minimum) and accurate to 1kg to ensure that your towing setup is safe and compliant. If you are experiencing any of the issues identified in this article or are just unsure of your tow ball mass, please contact your local vehicle and caravan weighing professional.