What ATM actually limits

Aggregate Trailer Mass is the most the van is allowed to weigh, fully loaded, standing on its own wheels and coupled to the car. It is stamped on the van’s compliance plate and it does not change with how you pack.

What the ATM does not do is answer the question buyers actually ask, which is whether a given vehicle can tow a given van. That answer comes from checking the ATM against four separate vehicle figures, and the tow rating is usually the least binding of the four.

The four figures the ATM is checked against

Braked towing capacity is the maximum trailer mass the vehicle is approved to tow. Of the 675 variants in our tow-vehicle table, 377 are rated at 3,500 kg.

Gross Combination Mass is the maximum for the vehicle and trailer together. The vehicle side of a GCM check is the vehicle and everything in it but not the ball load, because the ball load has already been counted inside the van’s ATM.

Gross Vehicle Mass is the maximum for the vehicle alone. Ball load lands on the towbar and is carried by the vehicle, so it comes out of the vehicle’s payload before your gear does.

Maximum ball load is a separate ceiling on the towbar itself, published by 645 of the 675 variants. The median figure is 350 kg.

Almost no vehicle can tow its rating while at its own GVM

Take the 341 variants rated at 3,500 kg that publish kerb mass, GVM and GCM. Ask a simple question: is GCM at least GVM plus 3,500?

For 38 of them, yes. For the other 303, no. That is 11 per cent.

GVM plus 3,500 kg against GCM	Variants
GCM covers it	38
Short by 1 to 400 kg	43
Short by 401 to 600 kg	135
Short by 601 to 750 kg	125

The median shortfall is 600 kg. The worst is 750 kg. The 38 that clear it are not the obvious ones: they are Nissan Patrol, the 70 Series LandCruiser, the KGM Musso, and the Land Rover range.

For everything else, towing 3,500 kg means the vehicle cannot legally be at its own GVM at the same time. The two ratings on the brochure were never meant to be added together.

What is left for you once the van is on the back

A cleaner way to see it: subtract kerb mass and 3,500 kg from GCM. What remains is every kilogram you are allowed to put into the vehicle while towing at the rating.

Across those 341 variants the median is 574 kg. The lowest is 205 kg. The highest is 1,380 kg.

Their median published payload, GVM less kerb, is 1,096 kg. So the typical 3,500 kg-rated vehicle can use about half its own payload while towing at its rating.

Two adults at 80 kg each plus 150 kg of gear is 310 kg. That alone exceeds the towing load budget on 19 of the 341. Add a 350 kg ball load and the total is 660 kg, which exceeds the budget on 226 of them.

Ball weight, from both sides

Ball weight is where the two datasets meet, and they do not meet neatly.

Of 599 vans with a published ball weight, the median is 185 kg, or 6.5 per cent of ATM. Only 7 publish a figure at or above 10 per cent of ATM.

Those are tare-state figures. Ball load rises as you load the van, and load lands behind the axles as often as in front of them. Manufacturer handbooks commonly specify a minimum nose weight of 10 per cent of the towed mass, which on a 3,500 kg ATM is 350 kg, not 185 kg.

On the vehicle side, 353 of the 645 published ball ratings are exactly 350 kg. Another 129 are 250 kg or less. So a 3,500 kg van loaded to a conventional 10 per cent ball puts 278 of 645 variants over their towbar rating on that check alone.

The payload squeeze

Ball load is not a separate allowance. It is payload.

Take the 357 variants rated at 3,500 kg that publish kerb mass and GVM. Median payload is 1,090 kg. Load two people and 150 kg of gear and then hang 350 kg on the ball, and the median drops to 430 kg remaining, with 21 variants already over GVM before anything else is packed.

Drop the ball load to 250 kg and no variant is over, and the median rises to 530 kg. A 100 kg change in ball weight moves 21 vehicles from illegal to legal.

A van and a vehicle, checked properly

The New Age Caravans Manta Ray Expedition 20ft Couples publishes a 2,600 kg tare, a 3,500 kg ATM and a 180 kg ball weight.

The Isuzu MU-X X-TERRAIN publishes a 2,195 kg kerb mass, a 2,800 kg GVM, a 5,900 kg GCM, a 3,500 kg braked capacity and a 350 kg maximum ball load.

Two people and 150 kg of gear, so 310 kg aboard.

Check	Sum	Result
ATM against braked capacity	3,500 against 3,500	At the limit
Ball against ball rating	180 against 350	170 kg spare
Payload after ball	2,800 − 2,195 − 310 − 180	115 kg left
Vehicle plus van against GCM	2,195 + 310 + 3,500 = 6,005 against 5,900	Over by 105 kg

The tow rating says yes. The GCM says no, and the GCM is the one that governs.

Run the same van against a Ford Ranger XLT Double Cab Pick-Up 4x4 3.0 V6, at 2,251 kg kerb, 3,350 kg GVM, 6,400 kg GCM, and the combination sits 339 kg under GCM with 609 kg of vehicle payload still free. Same van, same load, different answer, and the difference is not the tow rating, which is 3,500 kg on both.

What this means when you are shopping

Across the 475 variants that publish all four figures, 301 clear every check against a 3,500 kg van at a 350 kg ball and 310 kg aboard. Of the 348 rated at 3,500 kg or more, 19 fail on GCM, 25 fail on ball rating and 9 fail on payload.

So the rating is right about roughly six vehicles in seven, and wrong about the seventh. The problem is that the brochure never tells you which one you are looking at.

The tow guide calculator runs all four checks against your exact variant and a specific van. The vehicle finder runs them the other way, starting from the van.

Figures here are manufacturer-published; your vehicle’s compliance plates and handbook govern.