Axle Load in a Camper Van: The Calculation Nobody Does – and Why the Weighbridge Lulls You Into Safety
Reading time: approx. 8 minutes
The weighbridge at the filling station reads 2,930 kg, the limit is 3,000. So 70 kg to spare, all good? Not necessarily. The total weight is only one of three figures that have to be right. The other two are in your registration document under 7.1 and 7.2: the technically permissible axle load, front and rear.
That very vehicle, with 70 kg to spare on the scales, is 60 kg over the limit on the front axle in our calculation below. Without anything unusual on board, and without it showing on the outside.
The result up front: In a panel van it is not only how much you build in that matters, but where. The same conversion, the same parts, placed differently, shifts 135 kg from the front axle to the rear in our example – at exactly the same total weight. That is the difference between overloaded and legal.
Why an axle can be overloaded while the total weight is fine
A Ducato 30 may weigh 3,000 kg. Its axles are rated for 1,630 + 1,650 = 3,280 kg together. That difference is not a gift: it is the margin the manufacturer needs because the weight is never split fifty-fifty between the axles. Use it all up on one axle and you are overloaded – even if the scales still show room on the total.
On a front-wheel-drive panel van the weight sits mostly at the front. Engine, gearbox, cab, driver: an empty Ducato panel van already puts 1,380 kg on the front axle – that is what Dekra measured for promobil’s weighing report, 80 kg more than any other base vehicle in the same test. With a kerb weight of 2,000 kg, that leaves around 620 kg for the rear axle. Empty, the van carries a good two thirds at the front.
Then the conversion goes in. Kitchen, battery, water tank, bed, luggage: every part is shared between both axles – but not evenly. How it is shared depends solely on the distance from the front axle.
The lever rule in two lines
Share on the rear axle = weight × distance from the front axle ÷ wheelbase
Share on the front axle = weight − share on the rear axle
That is all there is to it. On the Ducato L2H2 the wheelbase is 3.45 m, the cab bulkhead sits about 1.20 m behind the front axle, and the load area ends at 4.32 m.
A 20 kg lithium battery right behind the driver’s seat (1.40 m) presses on the rear axle with 8 kg and on the front axle with 12 kg. The same battery in the rear garage (4.00 m) presses on the rear axle with 23 kg and takes 3 kg off the front axle. Everything behind the rear axle acts like a see-saw: it pushes down at the back and lifts at the front.
The example: the conversion from article 1
We use the same conversion we calculated part by part in How much does a van conversion weigh?: rear bed, kitchen block by the sliding door, tall cabinet, two overhead cabinets, 200 Ah battery, 70 l water tank, awning. Ready to travel with water, gas, two e-bikes, luggage and a passenger, that comes to 700 kg.
The vehicle: Ducato L2H2, kerb weight 2,000 kg, of which 1,380 kg at the front and 620 kg at the rear. The limits depend on how it is registered – the body is the same:
| Front axle | Rear axle | Gross vehicle weight | |
|---|---|---|---|
| Ducato 30 | 1,630 kg | 1,650 kg | 3,000 kg |
| Ducato 33 | 1,750 kg | 1,900 kg | 3,300 kg |
| Ducato 35 | 1,850 kg | 2,000 kg | 3,500 kg |
Variant A: evenly planned
Battery and inverter behind the cab, gas bottle next to the kitchen, water tank and luggage ahead of the rear axle, the e-bikes in the rear garage instead of on a carrier.
| Result | Ducato 33 | Ducato 30 | |
|---|---|---|---|
| Front axle | 1,630 kg | 120 kg free | used up |
| Rear axle | 1,080 kg | 820 kg free | 570 kg free |
| Total | 2,700 kg | 600 kg free | 300 kg free |
On the scales this looks comfortable. On the front axle it does not: on the 3.3-tonner it has 120 kg left while the total weight still allows 600 kg. On the 3-tonner it is already used up by a perfectly ordinary, lightly built conversion.
What that means for the rest of your payload
The kilos left on the front axle are not free kilos of payload. How much you may still load depends on where it ends up. For the Ducato 33 from the table above:
| Place | still possible | limited by |
|---|---|---|
| Cab, swivel seats | 150 kg | front axle |
| Directly behind the cab | 220 kg | front axle |
| Middle of the load area | 600 kg | total weight |
| Over the rear axle or behind it | 600 kg | total weight |
So the same luggage is allowed or not, depending on where it is stowed. On the 3-tonner this becomes a hard limit: there, only a few kilos are left at the front, but 300 kg behind the rear axle.
Same parts, different place
Variant B changes nothing about the conversion. Battery, inverter, water tank and gas bottle move into the rear garage, the e-bikes onto the rear carrier, the luggage to the back.
| What moves | To where | Rear axle | Front axle |
|---|---|---|---|
| E-bikes with carrier, 60 kg | garage → rear carrier | +35 kg | −35 kg |
| Luggage, 80 kg | middle → rear garage | +33 kg | −33 kg |
| Fresh water, 70 l | middle → rear garage | +28 kg | −28 kg |
| Battery and inverter, 29 kg | behind the cab → rear garage | +22 kg | −22 kg |
| Gas bottle, 21 kg | kitchen → rear garage | +14 kg | −14 kg |
The bottom line: 135 kg move from front to rear without a single gram being added: 1,490 kg at the front, 1,210 kg at the rear. The total weight stays exactly the same – the weighbridge would not show the difference.
The case that gets expensive
Now we build the same layout heavier, as in variant B of article 1: birch multiplex instead of poplar, a board bed instead of a sprung base, thicker panelling, a roof window, factory air conditioning, a tow bar, a second gas bottle, 112 instead of 70 litres of water. That is 235 kg more, distributed as in variant A, so with the technical gear at the front.
| Result | Ducato 30 | Ducato 33 | |
|---|---|---|---|
| Front axle | 1,690 kg | 60 kg overloaded | 60 kg free |
| Rear axle | 1,240 kg | 410 kg free | 660 kg free |
| Total | 2,930 kg | 70 kg free | 370 kg free |
That is the point: on the 3-tonner the scales say 70 kg to spare and the front axle says 60 kg too much. Anyone checking only the total weight sets off in good faith. On the 3.3-tonner the same conversion is legal – narrowly, and again it is the front axle that is the tightest figure, not the total weight.
And this is how it becomes legal again
Variant D: same equipment, same weight, only the distribution from variant B.
| Result | Ducato 30 | |
|---|---|---|
| Front axle | 1,560 kg | 70 kg free |
| Rear axle | 1,380 kg | 270 kg free |
| Total | 2,930 kg | 70 kg free |
Not one piece of furniture less, not one litre of water less. Only the battery, the water tank and the gas bottle in a different place – and the vehicle is within limits on both axles.
The catch at the back
After this calculation you might think: then just put everything at the back. It is not that simple.
Every kilo behind the rear axle takes load off the front axle – and the front axle steers and drives. The rear carrier with two e-bikes relieves it by 35 kg. That degrades steering precision and traction in the wet, and the long lever behind the axle makes the van sway more in crosswinds and quick steering movements. A rule of thumb is 40 to 60 per cent of the weight on each axle. More on this in Centre of gravity in a camper van.
The rear axle is finite too. In our example it stays relaxed because the conversion is light. With a scooter in the rear garage, a large tank at the back and a roof box, the calculation looks different – and then it tips the other way.
The biggest single lever is the water anyway. 112 litres are 112 kg; whether they sit in the middle or in the rear garage shifts 40 kg from one axle to the other. And the tank is the only item that changes completely while you travel. Placed between the axles, the distribution stays the same whether it is full or empty.
How to do it for your own vehicle
- Read the limits. Registration document, field 7.1 (front axle) and 7.2 (rear axle), plus F.1 and F.2 for the permissible gross mass. Those figures apply, not the brochure.
- Weigh it empty, axle by axle. On a public weighbridge, first weigh with only the front wheels on the platform, then the whole vehicle. The difference is the rear axle. Best done before the conversion.
- Place the heavy items first. Battery, water tank, gas bottle, fridge, rear garage: these five decide the distribution. Sheet furniture spreads over the whole length anyway.
- Water between the axles. The only item that goes from full to empty while you travel.
- Weigh again after the conversion, axle by axle – ready to travel, with water, gas and luggage.
VanLogic does exactly this calculation live while you plan. You slide the water tank backwards in the layout and see immediately what the front axle loses and the rear axle gains – for every piece of furniture, every component and every tank level. Axle loads, centre of gravity, remaining payload and the legal payload check sit side by side instead of in three separate calculations.
Try it directly in your browser — free, no download
Not bought a van yet? Then your weight budget is decided even earlier. At an identical 3.5 t gross vehicle weight, the common panel vans differ by up to 155 kg in payload — and a ±5 % tolerance is permitted on the kerb weight in the brochure. Which variant carries how much is covered in Which base van for a camper conversion?.
Australia and New Zealand: same lever rule, different paperwork
The physics doesn’t change at the border, only the names on the paperwork. In Australia and New Zealand the permissible gross mass is called GVM, and instead of fields 7.1 and 7.2 of a European registration document you need the manufacturer’s axle load ratings for your exact van and variant. Weigh axle by axle exactly as described above – on a public weighbridge or, in Australia, with one of the mobile weighing services.
Weight checks do happen: in a 2022 roadside weigh-in in Queensland, police found nine out of ten caravan combinations over a limit in some way (Drive). Knowing your axle loads before the weighbridge is cheaper than finding out there.
Conclusion
The gross vehicle weight is the best-known limit, but rarely the first one a panel van conversion hits. On a front-wheel-drive Ducato that is the front axle: it already carries 1,380 kg empty. In our example the same conversion was once 60 kg over the permissible front axle load and once 70 kg below it, at an identical total weight. The difference was only where the battery, the water and the gas were placed.
That decision costs nothing while you are planning and a rebuild afterwards. Calculate it first.
→ Calculate the axle loads for your conversion — vanlogic.app
Sources and assumptions
All figures retrieved on 23 September 2026.
- Vehicle data: Fiat Professional, technical data for the Ducato panel van – brochure dated July 2014 (permissible axle loads per version) and the current data sheet (wheelbase, overhangs, load area length). Kerb weight: ADAC car catalogue, Ducato 33 L2H2 130 Multijet (05/14–09/19).
- Weighed front axle load: promobil, base vehicles in a comparison test, Dekra weighing reports.
- Registration document fields: Zulassungsbescheinigung Teil I – codes and figures (BAVC).
- Component weights: as in How much does a van conversion weigh?, every part with a manufacturer’s or dealer’s figure.
- Australia and New Zealand (accessed 28 September 2026): Drive.com.au – Queensland caravan weight checks 2022.
- Assumptions: The empty rear axle load (620 kg) is the difference between kerb weight and the weighed front axle. The weighed vehicle is a Ducato panel van of the same series, but not exactly the same car – expect ±50 kg on yours and weigh it. The distance from the front axle to the cab bulkhead (1.20 m) is derived from wheelbase, rear overhang and load area length, because Fiat does not publish it; 10 cm of deviation shift about 2 kg per 100 kg of payload. The positions of the furniture and components are example values for a common layout. The current model (from 11/2023) is around 150 kg heavier, so the margins there are smaller.
About VanLogic: VanLogic is a planning app for camper van builders. Every piece of furniture gets a shape, dimensions, a material and a build method — the weight is calculated automatically, never estimated by hand, and feeds live into payload, axle loads and centre of gravity. Available for iOS and Android — and testable directly in your browser.