Load Limits & Associated Lingo

Knowing and understanding load limits is one of the most important aspects of owning a trailer. Failure to abide by these limits can lead to heavy fines or accidents. However, before we get into the rules and regulations of load limits, here’s a quick guide to some relevant terminology.

Tare weight – refers to the empty weight of the trailer.

GTM (Gross Trailer Mass) – the maximum allowable mass (set by the manufacturer) vertically placed on the trailer’s axle(s) while hitched to the tow vehicle, including the trailer’s payload (the maximum load weight for the trailer).

ATM (Aggregate Trailer Mass) – the tare weight of a trailer plus its maximum payload when not coupled to a tow vehicle. When in transit, a trailer cannot exceed this weight – a weight set by the original manufacturer/designer.

Payload – the trailer’s carrying capacity. In other words, this is the difference between the tare weight and its ATM. Modifications and additions to the trailer can quickly add to its carrying capacity and result in an overloaded trailer or the inability to carry items legally.

TBM (Tow Ball Mass) – the amount of weight a fully laden trailer imposes (vertically) on the tow ball of the tow vehicle. It isn’t usually a critical issue with small trailers unless the tow vehicle has a low TBM, as with many small cars.

The trailer’s VIN (Vehicle Identification Number) plate identifies the tare weight, ATM, GTM, and TBM.

The importance of sticking to the load limit

Abiding by the load limit for your trailer is extremely important as it can affect performance, safety, and insurance. Because of this, the most important thing is that you build the correct trailer for the hauling you plan to do.

Once you have the right trailer, you need to be aware of the implications of overloading, no matter how tempting it might seem. Overloading your trailer can lead to failing brakes, overheated transmissions, and broken suspension – all of which are extremely dangerous and can cause nasty accidents on the open road.

Besides overloading the trailer, one of the biggest mistakes many people make is loading the trailer incorrectly. Incorrect loading can cause a trailer to be off balance, making it difficult to control. All of our trailer designs are engineered to support the specified load, evenly distributed over the entire load area. Further engineering would need to be considered for point loads.

A rough guideline is to make sure about 60 percent of the total weight is in front of the axle. Fabplans designs specify the axle placement because getting it right is important for safety, along with enhancing how a trailer tows. You should also always remember to tightly secure any items to stop them from shifting during transit.

Another thing to check when carrying large loads is your tyre pressure. If you fully load your trailer and then drive with under-inflated tyres, you put yourself at a higher risk of tyre blow-outs and rollovers. Therefore, ensure you check the pressure of the tyres on your towing vehicle AND your trailer before setting out on the road.