Understanding Motor-home Payloads and Maximum Weights

Do you know your payload from your permissible mass? Ever thought about the weight of a full water tank or that TV and microwave you are about to load into your motor-home? If your answers are no then next time you hit the open road, destined for a few carefree days in your motor-home, you could be risking a huge fine. Perhaps even more significantly you could be seriously compromising your vehicle’s safety. The braking efficiency will be reduced and next to useless should the worse happen and you are involved in an accident. The vehicle’s stability will also be critically affected and may even be the cause of an accident. Last but not least, you are probably invalidating your insurance too.

No one is going to pretend that the subject matter of maximum weights is anything other than dry and decidedly boring, but understanding them, and ensuring you don’t exceed them, could just save you a pile of money and even your life.

Understanding the terms used

It doesn’t help that several terms, most using initials, are given to explain exactly the same thing.

The three terms which are most significant are

• Mass in running order (MIRO), sometimes called unladen weight
• Maximum technically permissible laden mass (MTPLM) also called ‘maximum gross vehicle weight’ (MGVW) or ‘maximum authorised mass’ (MAM)
• Payload

MIRO – This figure, which you will find in the owners handbook or by contacting the manufacturer, is the weight of your motor-home the second it was driven out of the factory for the very first time, all shiny and new. This figure includes any equipment fitted and given as standard in the motorhome’s sale description such as fridge, cooker, cupboards, fitted beds, toilet etc. It also includes the weight of your fuel tank filled to capacity and a driver (75kg).

MTPLM – You will find this figure stamped on a plate, typically found underneath the bonnet or on the driver’s door panel. It may also be in the vehicle’s handbook. This is the absolute maximum your motor-home can carry when you drive it so is the total of every single thing – the van, the fittings, any passengers, all essential habitation equipment (EHE) which includes leisure batteries, gas cylinders, fresh water in the tank, grey water in the waste tank, all your belongings, luggage and so forth.

PAYLOAD = MTPLM minus MIRO or, if you prefer your sums another way, you could say Payload + MIRO = MTPLM.

If maths was never your strong point and you have started to glaze over at this point then think of it this way. The weight of your van as it comes out of the factory is fixed. You then have a certain amount you can add into the van, up to the maximum allowed (MTPLM) and this is where you can start exceeding legal loads very easily without realising it. The essential habitation equipment will take up a healthy chunk of your payload allowance before you even start adding some rather necessary things like wife/husband/children, clothing, toiletries, food and cooking equipment.

Leisure batteries and full gas cylinders are very heavy and if you have two of each, then it will be even more. Other things which add considerable weight are bicycle racks, full or part full fresh water and grey waste tanks (1 litre of water weighs 1kg) and electrical equipment (a 14” old style portable TV weighs approximately 10 kg/ a 16” flat screen TV weighs approximately 4kg/ a compact microwave around 12kg).

Axle limits

In addition to overall weight limits, there are also set limits for each vehicle axle and loads must be evenly distributed so not to violate these restrictions.

How to weigh your motor home

Short of weighing every single item you place inside your motor-home, the easiest way to check its total weight is to take it to a public weighbridge. Make sure it is loaded exactly as it would be for any holidays or trips. You can weigh the total vehicle weight and also the rear axle weight. These two figures (total weight minus rear axle weight) will help you calculate the front axle weight – more maths!

Most weigh bridges charge a small fee for which you will be given a certificate which includes details of the vehicle weighed and the weights recorded.

Overweight? What do I lose?

When you are new to motor-homing, it is very easy to find yourself taking everything but the kitchen sink (“just in case…….”). You will eventually hone your essential list down the more experienced you get but in the beginning take a long hard look at what you have packed in and try to lose anything which isn’t absolutely essential. It may come down at this point to weighing individual articles.

The following are some easy ways to lose a little or a lot of weight.

• Food – Only take any food which you will need for your first night away and add to it when you need it. Food cans can be very heavy, as will such things as big bottles of drink, bags of sugar, crates of wine etc
• Gas - If you have 2 gas bottles in your set up only take one filled and invest the £2 it costs for a gas level indicator. Unless you are going to be somewhere remote, replacement gas is very easily come by and the indicator will warn you well in advance when you are getting low.
• Fresh water – Never travel with a full tank of fresh water. It not only adds considerable weight but may also affect your vehicle’s stability and negatively impact safe road handling.
• Grey waste – As for fresh water, empty before leaving home or a camp-site
• Toilet cassette – You really don’t want to be travelling with a full toilet cassette, creating human waste stew and resulting in less than pleasant smells as you drive. Toxic atmosphere aside, it adds significant weight.
• Cooking equipment – Weights of saucepans, china and glass casserole dishes and the like can add up alarmingly quickly. Buy lightweight versions and consider whether you really need the 6 saucepan set you have. Additionally, it might not be as classy as china but consider lightweight melamine crockery and use plastic instead of glass.

Motor-homes are stopped on a regular basis and weights checked, if there is a suspicion that laws are being violated.  Every year, motor-homers all over the UK are left with lighter wallets as a result. Reset your brain to start thinking MTPLM – who knows, it might even improve your maths.