Electric Brake Controllers and the Law
Sway energy is dampened by the following: friction at the tow ball, tow vehicle rear-tyre tread distortion and wind resistance. Swaying that lasts for two to three cycles is irritating. This sway, however, is usually harmless. As long as it stops within those two to three cycles. A friction sway damping device will be useful here.
If the swaying does not cease within two to three cycles, its source must be located and rectified before adding any sway damping device. Adding bits and pieces of remedial systems is counterproductive if the cause is not located and fixed first.
Begin Sway Cause Investigation - the Tow Ball
Greasing your tow ball is not a good idea, you need it to grip, not slip! Investigate the Alko AKS Stabiliser 50mm 3.5t tow ball with 4 special friction damping pads. This device is a good place to begin solving and preventing Caravan Sway.
Limitations of Friction Based Anti-sway devices
These friction devices are most effective at speeds of up to 60km/h with the benefit reducing as road speed increases. Not everything you need but better than having a slippery greased tow ball.
Practical methods of Reducing Caravan Sway
An average tow hitch overhang which is the distance from the rear axle to the tow ball is 1.25 metres for Australian vehicles. If your tow hitch has excess overhang, have a new hole drilled accordingly. Every centimetre of reduction is worth having. Utes with extended chassis and/or tow hitches are at major risk.
Best case is to have the loaded tow vehicle heavier than the loaded caravan. Be aware, however, that with caravans, it's their length, and where weight is distributed along that length that primarily affects the tendency to sway. Moreover, the longer the caravan, the lower its safe towing speed.
With long caravans, let’s look at over six metres or app. 20 ft. you need to have all heavy items as close as possible to the axles. Never load anything heavy at the extreme rear. It’s a bad idea to have spare wheels on a caravan‘s rear wall. Their actual weight maybe 40 kg or so. Their dynamic weight, however, becomes greater than 120 kg. If your caravan has them on the rear, reposition them in a slide-out cradle underneath the caravan‘s floor putting them as close to the axle as possible.
An Insight to Tyre Pressures and Sway
For towing Increase the tow vehicle’s rear tyres pressure by 5-7 psi or 30-50 kPa. Some misinformed caravanners increase the tow vehicle’s front tyre pressure as well as the rear. NEVER do this as doing so seriously reduces stability. Use the vehicle maker’s recommended front tyre pressure as for normal driving. NEVER inflate the front tyres higher.
Reducing Caravan Sway by Design Loading
An Australian-built caravan is now typically 6.0 to 6.5 metres in length. Its unloaded weight is typically 2100-2200 kg. The laden mass is typically 2500-3500 kg. These weight figures are an indication only some, however, are greater than 4000 kg plus. Bear in mind that excess length is even more of a stability issue. Excess weight is now a major issue for the newer generation of tow vehicles.
What is Tow Ball Weight and what are its Consequences?
Tow ball weight, or Tow Ball Mass is the weight applied from your caravan to the Tow Ball on your tow vehicle. When you are towing, the bulk of the trailer weight is taken by its wheels, and a small portion of it is passed onto the tow vehicle via the Tow Ball.
Low Tow Ball mass increases the probability of sway that is not self-correcting. You may read RV Books that can (legally) only suggest owners follow the makers’ recommendations. It certainly does not, however, endorse such recommendations. Research plus more research and nail down what is the right Tow Ball loading for your situation.