The shift from sedans to SUVs and light commercial vehicles (LCVs) as family transport is driven largely by practicality, but some motorists may be surprised by how little usable carrying capacity their vehicles actually offer.

SUVs offer generous luggage space and flexible seating, while double-cabs combine five seats with a versatile load box. However, a recent check of several models found that some may fall short of what owners expect when it comes to carrying passengers, accessories and luggage.

The problem is that usable carrying capacity is not always clearly stated in passenger vehicle brochures or specification sheets. Owners and prospective buyers therefore need to understand a few basic weight terms and do a simple calculation before determining whether a vehicle can meet their needs.

Understanding key weight terms

A vehicle’s tare mass is its weight including all standard equipment and fluids but excluding fuel. Although primarily used for certification, it can also be used as a basis for determining maximum trailer weights.

For motorists, kerb mass, which is the tare mass plus a full tank of fuel, is more useful. This figure, together with the Gross Vehicle Mass (GVM), is usually listed in vehicle brochures and specification sheets.

GVM is the maximum permitted weight of the vehicle, including the vehicle itself, fuel, occupants and cargo.

Any non-standard accessories, such as a roof rack, bull bar or canopy, must be included in the total. When towing, the downward force exerted on the tow ball, known as trailer nose weight, must also be counted.

The GVM is determined by the manufacturer and is used when calculating factors such as suspension travel, spring rates and braking performance. It also forms part of the vehicle’s homologation, making it a legal limit rather than simply a design specification.

Payload is the maximum weight a vehicle can carry without exceeding its GVM. It is calculated by subtracting the kerb mass from the GVM.

Although the term is more commonly associated with commercial vehicles, payload is equally important for passenger vehicles. In commercial applications, it may be described as gross payload, which includes the driver and passenger, or net payload, which excludes them and represents the weight of goods that can be carried.

For motorists who tow, gross combination mass (GCM) is another important consideration. Towing limits depend on factors including whether the trailer is braked or unbraked and whether the driver holds the appropriate licence.

Subject to the vehicle manufacturer’s specifications, an unbraked trailer with a maximum GVM of 750kg may be towed provided its GVM does not exceed 50% of the towing vehicle’s tare mass.

The 750kg trailer GVM limit also applies to drivers holding a Code B licence, the standard licence for drivers of vehicles with a tare mass not exceeding 3 500kg.

Holders of an EB licence may tow braked trailers with a GVM not exceeding the tare mass of the towing vehicle, again within the 3 500kg vehicle tare mass and trailer GVM limits.

What vehicle data plates tell you

Vehicle data plates do not generally provide all the information needed to establish usable carrying capacity. Owners may need to consult the vehicle brochure, specification sheet or owner’s handbook to determine the kerb mass.

Data plates provide a convenient reference for enforcement purposes and generally list the GVM, GCM, GA1 and GA2. The GA figures refer to the maximum permissible loads on the front and rear axles.

These figures allow for some flexibility in how weight is distributed, but the combined axle loads may not exceed the specified GVM.

Calculating whether load capacity meets family needs

Owners and prospective buyers should first consider how much weight they actually need to carry before checking whether a vehicle can accommodate it legally.

For example, a midsize five-seater family SUV carrying three adults, two young children and holiday luggage would require about 375kg of capacity. This allows for three adults at 75kg each, two children with a combined weight of 75kg and up to 75kg of luggage.

A sample of vehicles in this category found that most could carry between 375kg and 450kg, with some exceeding 600kg. However, despite their size, some models had capacities as low as 300kg, potentially limiting their suitability for larger families or heavier luggage.

At the other end of the scale, four adults travelling for a golfing weekend, together with golf clubs and even limited luggage, could require between 550kg and 600kg. This would narrow the choice to a handful of soft-roader SUVs or more rugged body-on-frame models.

Most double-cab 4×4 LCVs have capacities ranging between 800kg and 1 000kg. This generally provides enough room for many overlanding requirements, including a full load of adults, an aluminium canopy, rooftop tent, fridge or freezer, additional fuel, water and equipment.

For heavier loads, however, owners should check the vehicle’s actual weight once fully loaded to ensure it remains within the permitted limit.

Legal and financial risks of overloading

Exceeding a vehicle’s GVM is a contravention of the National Road Traffic Act and can result in a fine, AARTO demerit points and potentially the impoundment of the vehicle.

There can also be financial consequences. If a vehicle is involved in an accident and is found to have been overloaded, an insurer may repudiate the claim.

More importantly, carrying excessive weight can affect stability, handling and braking, particularly at higher speeds.

For SUV and double-cab owners, understanding the vehicle’s weight limits and checking what is actually being carried can help prevent legal, financial and safety problems.

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The post Weight watchers – understanding your vehicle’s load capacity appeared first on CAR Magazine.

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