Caravan Weight: Loading to be legal
All you need to know about watching the weight of your caravan
Our technical writer, chartered engineer, Terry Owen, unravels the jargon surrounding the weighty subject of caravan loading.
There is so much terminology surrounding caravan loading it can be totally confusing, even to the most hardened caravanner. We guide you through the jargon jungle so you can ensure your outfit is legal and, above all safe, for the road.
What is MTPLM?
MTPLM stands for Maximum Technically Permissible Laden Mass. This is the maximum weight, determined by the manufacturer, deemed to be safe to load the caravan to. On UK-spec caravans, the MTPLM is given on a plate near the entrance door.
The simple fact is that if your caravan is loaded so it is heavier than the plated MTPLM, it may be illegal to tow and could invalidate your insurance. While the MTPLM is not a legal limit, it is based on things which are, including the axle rating and the load rating of the tyres. It is therefore best to treat it as a legal limit.
Craig Thompson, from insurer, Caravan Guard, says: "If it were proven that damage to a caravan was caused due to towing while overloaded, an insurer could refuse to pay out for repairs."
In some circumstances, it is possible to have the MTPLM raised by what is known as a 'plate upgrade'; this is explained later.
Above: On UK caravans a plate similar to this should be displayed low down near the entrance door
And Ex Works Weight?
Ex Works Weight is the weight of a caravan as it leaves the factory. It is usually quoted with a tolerance in the range 3-5% to allow for manufacturing variations.
What about MIRO?
MIRO, or sometimes MRO, stands for Mass in Running Order. The term superseded Ex Works Weight on caravan weight plates in 1999/2000.
The way MIRO is calculated has changed over time. Up to and including the 2010 model year it did not have to include gas bottles, water in water heater, toilet flush water, water in onboard tanks or the leisure battery. In practice it was little different from the Ex Works Weight quoted previously.
Clearly this was unrealistic and so, for 2011, the rules changed so that all the above, apart from the leisure battery, had to be included. If an onboard water tank had a capacity of 30 litres it had to be assumed that it was 90% full, thus adding 27kg to the MIRO figure.
It may seem strange that the leisure battery was omitted but, in mainland Europe most caravans do not have leisure batteries as they are only ever used with hook-ups.
For 2015 the rules changed again so that manufacturers can now specify how much water they have included in their MRO calculation. This applies not just to storage tanks but to water heaters and associated pipework too. Most manufacturers have elected to choose zero water, perhaps on the basis that they would prefer us to tow without any on board.
Your caravan's handbook may tell you how the MIRO has been calculated.
A typical MIRO calculation for 2011
|Ex works weight||
|Gas bottles (2x 5kg BP Gas Light)||
|Water in the water heater||
|Water in the 30 litre on board tank||
|Toilet flush water||
|Leisure battery (not included)||
A MIRO calculation for the same caravan in 2015 and beyond
|Ex works weight||
|Gas bottles (2x 6kg Calor Lite)||
|Leisure battery (not included)||
What is Essential Habitation Equipment Payload?
This is a figure sometimes used by manufacturers to allow for the weight mass of items required for the safe and proper functioning of the caravan.
This comprises items including gas cylinders and water in the water heater. The leisure battery is normally included under personal effects; see the table above-right.
And Optional Equipment Payload?
These are items made available by the manufacturer over and above the standard specification for the caravan. For example, a dealer special model will have extra equipment that might include thicker carpets than those on a standard caravan, or a wheel lock as part of the package. While such items are good to have, they do eat into the allowance for personal effects.
And the User Payload?
This is the difference between the MTPLM and the MIRO. It includes the personal effects and optional equipment allowances. When designing a caravan, manufacturers try to ensure the user payload is at least the same as that required for personal effects; see the table above.
What is the Personal Effects Payload (PEP)?
The PEP is an allowance for those items a user can choose to load, that are not part of the essential habitation equipment or optional equipment. It is calculated using the following formula: PEP= 10L + 10N + 50(kg), where L is the body length of the caravan in metres and N is numbers of berths.
So, a five-metre, four-berth caravan should have a PEP of: 10x5 + 10x4 + 50 = 140 kg
Typically, the figure of 50 kg would allow for items like these:
Is there any difference with continental caravans?
Yes, continental caravans simply have a plate showing the maximum loading of each axle and a total figure. It is illegal to exceed this total figure. The plate is often located in the gas locker.
Where does a caravan mover fit into all this?
The weight of a caravan mover counts as part of the personal effects payload. As a typical mover weighs about 30kg, it equates to much clothing, or food and drink, which may have to be carried in the car instead of the caravan, or even left behind.
The same applies to fitted solar panels or satellite dishes. All these items permanently reduce the maximum weight of personal effects you can carry. And don't forget your awning. These can weigh in at a hefty 30kg.
It's all a bit confusing - how can I avoid overloading my caravan?
- The easy way
Take it to a public weighbridge. Typically, this will cost between £5 and £10 and you'll come away with a certificate telling you the weight of your caravan. There is a useful government website to help you find a local weighbridge (gov.uk/find-weighbridge) or simply type the words 'find weighbridge' into a search engine.
As an alternative to visiting a weighbridge, you can use a device like Reich Weight Control. This is essentially a load cell that measures the weight of each wheel as you drive slowly over it and then adds them up to give the total weight of the caravan. If you regularly load your caravan to the gunnels, such a device can be a Godsend in keeping you on the right side of the law.
Below: Reich's Weight Control (Amazon - £159.50) measures one wheel at a time
- By calculation
You can calculate how much your caravan should weigh by measuring the weight of everything you've put on board and adding that to the caravan's MIRO.
A set of luggage scales is ideal for this, along with some large bags to weigh many items at once. Don't forget to include the weight of the leisure battery and any extra gas, plus water not included in the MIRO calculation for your caravan.
If you think your caravan may be nearing its MTPLM, bite the bullet and get it weighed!
What is a plate upgrade?
In order for a caravan to be towed by a wider variety of cars, manufacturers sometimes restrict the MTPLM to a lower figure than it needs to be.
If your towcar is capable of handling a heavier caravan and you want to carry more weight, ask the supplying dealer if a plate upgrade is possible for your particular caravan. If it is, they will arrange it for you, and supply a new plate with the relevant paperwork. Be prepared to pay an administration charge for this.
Above: The MTPLM of this Elddis caravan is less than the rating of its axle, suggesting that an upgrade may be possible. The figure of 100kg is the maximum vertical loading of the hitch
Does it matter how I load my caravan?
For safe and stable towing, it's not just the weight of the caravan that's important but how that weight is distributed within the caravan. Heavy items should be low down near the axle. Weight placed at the rear of a caravan may cause it to become unstable, especially at speed and in crosswinds.
Above: For good towing stability a caravan should be loaded like this
Is noseweight important?
Noseweight is the downforce exerted by the caravan onto the car's towball. It is essential to have some noseweight for stable towing.
The accepted figure for caravans is 5-7% of the MTPLM. A caravan with an MTPLM of 1200kg should therefore have a noseweight of 60-84kg, but the actual figure should not exceed the limits of the car, its towbar, and the caravan hitch assembly. Within these limits, the higher the noseweight, the better.
Most UK caravans have a maximum noseweight rating of 100kg. The towbar noseweight rating should be given on a plate on the bar itself. The car's limit should be given in its handbook.
Above: This towbar label shows a noseweight limit of 150kg
Noseweight can be adjusted according to how the caravan is loaded. It can be measured with a purpose made gauge or some blocks of wood and a set of bathroom scales.
Above: A Reichs Noseweight guage - available on eBay for £47.99
Above: Checking noseweight with bathroom scales
Caravan Nose Weight Guage
Buy them on eBay for £36.95
Buy them on Amazon for £32.72
How heavy should my car be?
Above: For stability the towcar should always be heavier than the caravan
Industry advice (and common sense) says the kerbweight of the car should always be greater than the MTPLM of the caravan. Ideally, the caravan's MTPLM should not exceed 85% of the car's kerbweight, although experienced towcar drivers can take it to 100%. If you go beyond this, the outfit is likely to become unstable at speed and may be considered unroadworthy by the police.
Regardless of the weight ratio, it always makes sense to carry heavy items, like awnings, in the towcar whenever possible. The heavier the towcar is compared to the caravan, the more stable the outfit will be.
Why can't I just tow to the car manufacturer's Towing Limit?
All cars approved for towing will have a maximum braked trailer weight stipulated by the manufacturer. In some cases this can be considerably more than the kerbweight of the car. Take, for example, a Ford Mondeo Titanium 2-litre Duratorq TDCi hatchback. This has a kerbweight of 1578kg and a maximum braked trailer towing weight of 2000kg.
The interesting thing is how the towing limit is arrived at. According to European regulations, a car's towing limit is the maximum weight at which: 'The vehicle towing a trailer must start the combination – laden to its maximum mass – five times on an uphill gradient of at least 12% within five minutes.' In the case of the Mondeo above, this clearly doesn't mean it's safe for it to tow a 2000kg caravan. There is also achievable noseweight. For a 2000kg caravan, it should be 100-140kg but the Mondeo has a limit of 90kg.
A car's towing weight limits should be shown on its weight plate. This may be under the bonnet or on a door pillar. To find the kerbweight, you'll need to consult the handbook.
Above: This Subaru weight plate shows the car has a maximum allowable weight of 1945kg, maximum train weight of 3745kg and maximum front and rear axle loadings of 1070kg and 1060kg
What is Gross Train Weight (GTW)?
GTW is the maximum combined weight of the car and caravan. It is a legal limit, which should be stated by the car manufacturer for newer cars. It may be the sum of the car's Gross Vehicle Weight and Towing Limit or it may be set lower than this.
Above: Train weight is the weight of the car and caravan
Towcar matching services
If you're thinking of changing your car or caravan, it makes sense to use a towcar matching service. These hold a large database of car and caravan weights and can quickly find suitable matches from a given starting point including a particular car or caravan.
Caravan's outandaboutlive website has a Towmatch service. You can put in the details of your car and a list of caravans suitable for it will pop up.
Members of the two big Clubs can take advantage of their online matching services, too, or you can use the NCC's TowCheck service, for which there is a charge.
What about driving licence restrictions when towing?
Contrary to what some believe, those who passed their test after
1 January 1997 can tow a caravan. However, the combined weight of the car and caravan (Gross Vehicle Weight plus MTPLM) must not exceed 3500kg.
To tow an outfit heavier than this, these drivers need to pass a further test to get a B+E entitlement on their licences.
Once gained, they can tow trailers up to 3500kg provided the train weight of the outfit does not exceed 7000kg.
Drivers with tests passed prior to 1 January 1997 are generally entitled to drive a vehicle and trailer combination up to 8250kg. If renewing your licence at age 70, ensure sure you keep a copy of the old licence showing your entitlements. It has been known for new licences to be issued with some entitlements missing.
If you lose your licence for any reason, you will be treated as a new driver when it is eventually returned to you.
Ten tips for saving weight
|1||Take everything out of your caravan and put back only those items you will need in the immediate future. You could be amazed how much you've been carrying.||20kg|
|2||Carry one or more gas bottles in the car (always upright).||10kg|
|3||Carry the leisure battery in the car.||20 kg|
|4||Drain the water system before towing.||12kg|
|5||If your caravan's table is heavy, invest in a lightweight one.||5kg|
|6||Carry security devices, including wheel and hitch locks, in the car.||10kg|
|7||Replace pottery/china items with melamine, and glassware with plastic.||5kg|
|8||If your caravan has loose carpets, remove them. Make do with a couple of small mats.||10kg|
|9||Buy food and drink at your destination rather than taking it with you.||10kg|
|10||Invest in a portable solar panel rather than a fixed one. You will get away with a smaller panel and need only take it when necessary.||5kg|
Total potential saving
Above: Draining the water heater and associated pipework can save more than 10kg in weight