A motorhome payload is the difference in weight between the mass in running order (MIRO) and the maximum permissible technical laden mass (MPTLM). Or to put it simply – the weight you can carry in a motorhome without overloading it.
When we were first looking for a motorhome the payload was something that didn’t even enter into the equation. It never really occurred to us that there would be a maximum limit of the amount of stuff you can take with you.
We thought you could just load these vehicles up with whatever we could fit in there and everything would be fine. After all, is that not the purpose of owning a motorhome, you can take all your stuff camping with you?
Imagine our shock when we found out that we were limited to what we could take with us. Disaster!
Of course, after a little bit of thought, it makes complete sense. There is a maximum weight that these vehicles can carry just like any other vehicle on the road and the one thing you don’t want to do is to overload them. A motorhome is hard enough to drive when it is not up to its maximum weight.
What is the Payload of a Motorhome?
One of the main problems is its very difficult to know what your payload is. In the manual for the motorhome, the payload is specified quite clearly. There are two things you have to know the MIRO and the MTPLM. Simple
MIRO is the Mass in Running Order. This is the weight that the motorhome leaves the factory plus a full tank of fuel and the weight of the driver (75kg) and some basic equipment. It’s the basic weight of the motorhome that is required to use and drive it so includes all oils and fluids, spare wheel and tools for changing the wheel.
Basic equipment according to a 1995 manual includes;
Freshwater tank filled to 90%
Gas bottles x 2 – filled to 90%
Boiler – 12l
MTPLM – is the Maximum Technical Permissible Laden Mass. This is the absolute maximum that the motorhome can weigh. If you go over this figure then your vehicle is overloaded and you can be fined if you are stopped and weighed. This figure is on a plate in the engine bay along with the maximum loads for the front and rear axles.
So the payload is the difference between the MIRO and MTPLM weights. The larger the difference the better.
I would say this is the basic payload but of course, it’s not quite that simple.
Erosion of Payload
The problem with an older motorhome payload calculation is it does not account for any additional equipment that has been put in over the lifetime of the vehicle. Sometimes it can be very difficult to see what additional equipment has been added and especially to know what the weight of that equipment is.
Our motorhome, for instance, has several pieces of equipment fitted to it that are now defunct. The only way I found these was by crawling underneath the Motorhome. This is when I found out that there were additional suspension airbags, now not used and are actually burst.
There is also some automatic levelling equipment again most of the been removed but a lot of it is still there creating more weight and that needs to be on the Motorhome probably if I remove that all we would have an extra 10 kilos onto the payload.
That is just one piece of the extras we have, Other extras include
solar panel and related equipment,
amplifier and speakers (essential),
a massive fan on the roof (I don’t think that is standard but probably weighs a good 20kg),
As well as other items which I thought were part of the initial MIRO but are not.
Here are some items from the Hymer manual – 1995 which are not part of the standard equipment and will eat away at your payload.
Wastewater tank, insulated
Heated and adjustable electric mirror
Car radio Cassette
Pull Down Bed
Front Storage Compartment
Roof Rail with Access Ladder
Front Skylight with shade
Electrically operated Step
Bike Rack for 2 Bicycles
Bike Rack for 3 Bicycles
Cabin floor mat
Remote gas switch
Gas socket with stopcock
Lift-tilt skylight 960x655mm
Electric steady legs x 2
Steady legs x 2
Insulation mat for driver cabin window
12V Airconditioning unit
240V airconditioning unit
Ridgid motorbike rack
Extendable motorcycle rack
Pull-down motorcycle rack
Multiple load rack B – Pair
Multiple load rack B, high – Pair
Satellite ariel Mobisat BAS60
Satellite ariel Mobisat CAP 100
Oyster 65 Satellite Antenna
Oyster 85 Satellite Antenna
Rear Mud Flaps x 2
Solar Installation 1 x 54W, regulated
Solar Installation 2 x 54W, regulated
Thetford spare cassette
TV swivel console
Underfloor sliding drawer
Additional heater – drivers cab
Second living area battery
As you can see there are a few surprising things on the list that all take a little of the payload and that’s before you have put any of your own stuff in there.
Don’t forget that even before your clothes you may want crockery, bedding, toiletries, TV, toys, books, animals, bikes, food and some people even manage to squeeze in beer!
You can see how easy it is to push the weight of your motorhome up to and beyond its maximum load.
Placement of payload
Another problem with payload is where it is put. Once you find out how much weight you can carry legally there’s the problem of how to distribute the weight evenly.
The weight in a motorhome has to be distributed evenly so that the weight is equally spread on the two axles, or at least so as not to overload the rear axle – which we have difficulty with.
This is more tricky than it seems as most of the space for carrying equipment is at the rear of the Motorhome. Our motorhome also has a 2 m overhang from the centre of the rear wheel.
This means that the rear wheels act as a pivot, the more loads you put on to the rear the more load comes off at the front. This has the effect of causing the front to be very light which can affect steering and grip at the front, making driving quite dangerous.
Also, it’s important to make sure that the load is not over to one side either. This will have the effect of pulling the Motorhome to one side.
So before you load up with all the gear you could ever want and force it on board you have to really think about where it’s all going to go.
Weight distribution is very important in a motorhome.
How adding weight to the back changes things
The problem with the overhang at the back of the Motorhome is there most of the storage areas are in that overhang. This makes it relatively easy to overload the back of the Motorhome which is why it’s so important when you get the motorhome weight correct at the front and rear axles as well.
Now, as has been said, weight at the back can act as a pivot and lighten the load at the front this has the effect of adjusting grip and handling of the Motorhome and not much fun when you’re driving.
There is a way that you can measure the load reducing factor and work out how much effect the rear load is having on the front of the Motorhome just by using a simple formula the formula is shown below.
Overhang – distance from the centre of the rear wheel to the rear of the motorhome in millimetres
Wheelbase – distance from the centre of the front wheel to the centre of the rear wheel in millimetres
Original Front Axle weight – the original weight at the front axle in kg
New front axle load = Original Front Axle Load – (Added Load x (overhang/wheelbase))
So if I wanted to add a bike rack onto the motorhome which weighs 60kg including the rack and bikes we can calculate like this.
Original front axle load – ??
Added load – 60 kg (bike rack)
Overhang – 2000mm
Wheelbase – 4200mm
New front axle load = Original front axle load – (60 x (2000/4200)) = Original front axle load – 28.6kg
So by adding 60kg to the rear of the motorhome 28.6kg is taken off the front axle due to the pivoting effect. Add a few heavy items to the rear locker and fill up the water tank and all of this will have the effect of taking the load off the front wheels.
Our motorhome has the additional problem of having the water tank past the back wheel which means that has to be included in the pivot formula so the more water we carry the more effect that will have on the front wheels. The water tank is closer to the rear wheel than the bikes so won’t have the same effect but will have some.
This may have been a slight oversight by Hymer. What this means for us is that it could quite easily be 200 kg of weight after the rear wheels that would be 100kg for water 65kg bikes and about another 40 kilograms in the large locker at the back.
This is why you have to be very careful with both the size of your payload and distribution. You want more weight in the centre area of the motorhome and closer to the front and that should help even things out a bit.
Get Your Motorhome Weighed
Of course, to work out these figures accurately you have to get the motorhome weighed at local weighing stations. Most will allow you to put on the front wheels and the rear and then the whole motorhome. This will give you a good idea of the load and distribution of the weight in the motorhome and is really the only way you can find out if you are running overloaded.
I like to load up the motorhome completely and get it weighed and check the axles.
Make sure you load it up for going on holiday and don’t forget to include your passengers. You will be given a slip of paper with the weights and from that, you can calculate the distribution of loads within the motorhome.
A lot of people overlook getting their motorhome weighed but it is quite important. Overloading a motorhome can really change the handling and affect other things like the brakes. This can be really dangerous in a 3 and a half tonne motorhome. I like to treat our 30-year-old braking system with care as well as looking after the suspension.
Make sure you know what is in your motorhome and don’t let all the little stuff build-up (easier said than done) before you know it you will be running overweight. Just like this guy…..