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Weight Distribution – Towing Edition

23, Nov 2020 in Tips

Something never really dwelled on is how a vehicle and trailer is packed when heading off for a road trip. Sure, we have all played the game of Tetris, rearranging and repacking vehicles to make sure every morsel of space is utilized. Then you have to get the kids and dog in the car.

But there is a little known science to how a car is loaded. Caravan, Boat and trailer manufacturers know of this ‘Stone Cutters’ sceince, and a very select few of the general public do as well, this knowledge is passed through from generation to generation via hours of countless profanities just as Mum comes out with ANOTHER bag, to which Dad responds… ‘Nothing else will fit’…

That last bit may have been anecdotal, but I am sure you get the picture.

More specifically, trailer weight distribution is very important for safety when on the open road. At 100km/h any trailer can be a very dangerous implement and how you place your weight on the trailer can be the difference between arriving to your destination safely and violently veering off the road out of control in a vein attempt to save your trailer as it tries to overtake you. There are too many Dash Camera Videos on the internet that highlight the dangers of Towing an ill weighted trailer.

For the purpose of this Blog, you will need to understand TBM or TBW.

TBM (Tow Ball Mass) or TBW (Tow Ball Weight)

The maximum permitted weight to be placed on the tow ball by the coupling. It is the difference in weight between the caravan/trailer on the tow vehicle and off. The ideal for this is considered around 10% of the weight of a fully-laden caravan or camper trailer. Care should be taken to check with some imported caravans as they may be considerably less than 10%. Too much ball weight can affect the tow vehicle’s stability, steering and braking, whilst too little ball weight can cause the caravan or trailer to become unstable and sway.

One way to calculate the ball load/tongue weight is the difference between the ATM and the GTM.

 

Now that you are up to scratch on the terms, its time to put these to practice.

Each car with its towbar will have different capabilities and weights it can carry. But the first and most important weight is the TBW, this is the weight added to the rear of your car. What ever you do you do not want your car looking like those Commodores who seem to think that having your car looking as if its towing an invisible 35 foot Luxury Caravan. So make sure your TBW is not over loaded.

Next is distributing the movable weight, in short you want a majority of the weight located over the axles of the trailer and as low to the ground as possible.

The main reason is because the Axles is the pivot point for the caravan. The further weight is away from that pivot point the more inertia there is to destabilize the caravan. Having too much weight towards the front of the trailer creates more TBW which will cause the steering wheels of the car to be lifted off the ground giving the driver less control.

On the flip side if the trailer is overloaded in the rear the light ball weight will mean the rear of the car. I am sure you can imagine this also has an adverse effect on the ride quality and safety of the vehicle.

 

Essentially to tow safely this summer and for any road trip, please ensure your weight is distributed in the correct way to avoid being one of those Tourists who end up on Dash Cam Videos Australia