Tow ball mass is one of the most important elements in your towing setup to help ensure stability.

Think of a caravan as a seasaw with the axle(s) as the pivot point. So when more weight is loaded at the front the towball mass increases and when more weight is loaded behind the axle(s) the towball mass (TBM) reduces.

Most people are familiar with the 10% rule were the towball mass should be 10% of the trailer/caravan weight (GTM). In modern caravans its often 8-12% with anything outside this range especially under that will be a leading contributor to instability and trailer sway.

So as an example, we had a customer with a dual axle caravan that was balanced and level but they were wanting to know why they often ended up with caravan sway when being overtaken or overtaking a B-double or when hitting a rough section of road on a bend. Each time they were travelling within the advisory signs or under the speed limit.

After completing the weighing session it was found that whilst they were well within their GTM, ATM, and axle weights were well balanced, there was nothing on the rear bar other than the spare wheel and where towing level with a calculated towball mass of 4.7%. It was well under the 8-12%.

Since they were looking to do more off grid trips and had plenty of wriggle room in GTM and ATM installing a 3rd water tank provided a way to increase the tow ball mass by a full 100 kg with the view to use it last.

After the tank was installed we did a reweigh and found it had increased the tow ball mass percentage to 8.7%. Whilst it was on the low end of the 8-12% range the feedback on the van’s stability was much improved with no instance of sway even when overtaking or being overtaken by B-doubles or hitting rough sections of road on bends.

This is just one example of where having the right tow ball mass improves the safety of the towing setup.