There is something of a gap in understanding and awareness when it comes to payloads and correctly and safely loading tourers when you compare caravan owners and motorhome owners. With regards to caravans, when the nose weight is either too low or too high, the consequences are very obvious, because the caravan pitches down or up while you are towing, and snaking can happen as a result too.
When motorhomes are overloaded or the weight hasn’t been properly distributed across the vehicle, the consequences are not as easy to spot right away because the weight is spread across a much larger area and wheels are in each corner.
However, it should not be disregarded, because driving a motorhome that is not loaded correctly or overloaded can be illegal, and even if it isn’t, it may invalidate your insurance policy and could cause problems with handling and braking.
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A Problematic Misconception
The reason so many motorhome owners make mistakes is because of a problematic misconception when it comes to the differences in payloads between motorhomes and caravans. Take the example of caravans. Now, there is usually a difference in payload allowance for caravans that have single and twin axles. However, it is most commonly around the 150kg mark.
With regards to campervans and motorhomes, however, the payload is generally a lot higher. Think 1000s instead of 100s of kilos. Thanks to this, many motorhome owners possibly have a false belief that the belongings they take along are never going to max out such a high weight allowance.
As you will see from the following post, as we look at the subject of payload allowances and loading motorhomes safely, this is simply not the case.
Understanding the Difference Between Caravans and Motorhomes
One of the biggest differences between caravans and motorhomes, from a payload allowance point of view, is what is often referred to as the rear garage in its layout. Although caravans have a rear locker that extends right across the caravan’s rear, and they are useful for storing long items like awnings, poles, and leisure equipment like skis etc, they do not really fit the bill of a garage.
Motorhomes, on the other hand, have a much higher storage locker that sits behind the vehicle’s rear axle, which is normally referred to as the garage. Most motorhome owners use this garage to store leisure vehicles like mopeds, scooters, and bikes.
Some motorhomes also have a bike rack that is fitted at the rear of the vehicle. This can lead to what is known as the “overhanging problem” as that weight is actually behind the vehicle’s rear axle, which means it is multiplied.
Understanding Motorhome Weight Plates and Payloads
Before you can actually start loading the motorhome and doing it safely, it makes sense that you need to know what its actual weight limit is. To find that information out, you need to locate, read, and fully understand what the weight plate says about your vehicle. The weight plate features crucial information about the limits you need to remain within to stay legal while driving and maintaining your vehicle insurance and warranty.
Two crucial terms and measurements you need to understand about your motorhome are normally included on the weight plate and those are MTPLM and MIRO.
Without deviating too much, we’ll briefly explain what each of these measurements means.
- MIRO – MIRO stands for Mass In Running Order and refers to the weight of the touring vehicle without any payload.
- MTPLM – MTPLM stands for the Maximum Technically Permissible Laden Mass and refers to the total amount a motorhome can weigh to be roadworthy and fully legal. The easiest way to think of it is – MIRO + Payload = MTPLM.
A common misconception that is not always true in every motorhome’s case is that the larger the touring vehicle, the larger its payload capacity. For example with a panel van conversion motorhome, you can actually have a bigger payload capacity than a coach-built vehicle that is the exact same size.
Why is that? Panel van conversions use commercial chassis, while coachbuilder vehicles use lightweight AL-KO chassis.
What is Your Real Remaining Payload Capacity?
If you have got this far in this guide, you will have worked out a weight for your payload capacity. Before you start planning trips and loading your tourer, you need to grind to a halt, because while you are in a better position than you were when you first started reading this post, you are still only part of the way there.
That number you have in mind is merely a starting point. You next need to look at your vehicle and figure out what else is eating into that payload. For example, if you have an air conditioning unit, satellite dish or solar panels, they will have to be subtracted from the payload capacity.
It doesn’t stop there, as you need to discount the weight of the gas bottles you are taking along on trips too. Although it may not seem it, gas bottles can really have a huge impact on your payload allowance, particularly if they are steel canisters.
Weighing Your Motorhome and Personal Belongings
Ideally, when you know the real remaining payload capacity you have for your motorhome, it is a good idea to weigh everything you intend on taking with you as you load it onto your tourer. This will help you determine whether or not you are within the payload allowance.
There are two ways you can weigh everything you plan on taking and the vehicle itself and that is by either using portable weigh scales or a public weighbridge.
The latter is highly recommended, though, as it will provide you with the most accurate figures. At Caravan Helper, we suggest you use both because when you use portable weight scales to weigh all your belongings you can reduce the number of trips you may need to make to the nearest weighbridge.
Upgrades that Can Help Increase Your Payload Allowance
In some situations, if the work can be carried out on your vehicle and you need a bigger payload allowance, you can have certain upgrades made. One is referred to as up plating your motorhome weight plate. You will actually find that a lot of commercially available motorhomes have been down plated before they have been sold to 3,500kg, to make it possible for more people to feel comfortable and safe driving them.
In addition to having your motorhome up plated, it is a good idea to have the suspension on your motorhome assessed.
What About the Overhang Issue That I Keep Hearing About?
You are right to be concerned about the problem of overhang with your motorhome, but how serious this issue is and whether you have an issue at all depends on how long the overhang is past the vehicle’s rear axle and if your vehicle has a rear garage and what you are going to store in it. That’s not to say if you don’t have a rear garage you won’t have any overhang issues.
For example, if you install a scooter or bike rack onto your motorhome, there is potential for an even more serious and extreme overhang issue than simply having a slightly overloaded rear garage. This is because the scooter or bike rack is even further from the pivot point of the rear axle.
Another potential issue may arise if you intend on towing with your motorhome, as towing a trailer or something else will increase the weight that the motorhome rear has to deal with.
More About the Issue of Overhangs
Overhangs relate to leverage and pivot points. Basically, as we alluded to earlier, the pivot point on your motorhome is the rear axle. The leverage your motorhome has comes down to overhang length that stretches past the rear axle. To put it another way, the distance from your motorhome’s rear to its rear wheels.
When there is greater force weight applied past the rear axle, there is less load placed onto the front axle. This means the front wheels may have less traction, which is important to consider as they play important roles in both steering and braking.
Now For the Science Bit
We’re sorry, but if you are serious about working out the precise payload allowance and want to avoid overhangs, you need to get to grips with some number crunching. Firstly, you need to measure the distance between the wheelbases, both the front and rear axles. You also need to work out the distance between the overhang and the rear axle, as this is the point where the additional weight pressure will be placed.
It’s also important to remember that if you have a scooter or bike rack installed, you need to take the measurement from the back of the rack, not just the motorhome’s back surface.
The following formulas will help you determine whether you have an overhanging issue on your motorhome or not. Bear in mind that when W is mentioned this refers to the wheelbase length and the O refers to the length of the overhang.
The first calculation will give you the new front axle load or new F for short.
F – ((Lx(o/W))
Once you have that number, you can then figure out the new rear axle load, remembering that includes the scooter or bike rack weight.
The New R is worked out by R + L + F (F – New F)
You then need to check whether that number falls within the legal maximum weight for your motorhome rear axle and will then know with great accuracy whether you will have any overhang issue and how serious it will be.
Summary
The main goal of publishing this post was to draw your attention to the fact that the motorhome overhang issue is a very real thing and something that many overlook and disregard. This is important to keep in mind when you are loading your motorhome if you want to do it safely and legally.
Simply weighing your belongings and using the weight plate for reference only gives you one part of the whole picture. We hope this guide helps you to work with the right numbers and stay safe and legal when you are loading your motorhome and heading out on the road.