What do I need to know - before I can tow?

Vehicle Weights

The owners handbook for your car will be invaluable here, as will a knowledge of the MTPLM of your Eriba.

The legal situation is quite easy:

1. The caravan must weigh less than the difference between the Gross Train Weight and the Gross Vehicle Weight printed on the car VIN data plate.

2. The caravan must weigh less than the maximum braked trailer weight mentioned in the owners manual.

3. The car must be loaded so that neither of the axle loads is exceeded - this is particularly true of the rear axle load after hitching up the caravan.

Sounds easy - and indeed it is, with the exception of Renault who perversely quote the maximum braked trailer weight with only the driver on board - and with every model of car from this car maker, care is needed to ensure that you don't break the law by overloading when you carry more than the driver.

Nose-Weight

To ensure a stable ride and towing experience, the caravan must be loaded so that the caravan coupling press down onto the car tow bar with a suitable nose-weight.

But what is a suitable nose-weight?

Well it must be more than 25kg. And Hymer recommend it should be at least 4% of the caravan MTPLM, so if your Triton had a maximum weight of 1000 kg then the nose-weight should be at least 40kg.

But the nose-weight applied by the caravan must be less than the design limit of the Eriba tow-coupling (usually 75kg) and less than the design limit of the tow-bar (typically also 75kg - but you must check the data card attached to your car's tow-bar).

Kerb-Weight and the 85% Guideline

Another item you'll hear about is the UK 85% guideline for caravan matching. This has no legal standing and it's certainly NOT a rule whatever others may tell you, but it is a useful guideline to stability and a happy towing experience.

The idea is that read your car handbook for the kerb-weight as defined by the EU MiRO directive (it is also printed on your car V5 "logbook"), and also look up the caravan MTPLM. Then calculate the ratio as follows:

Ratio = 100 x (caravan MTPLM) / (car kerb-weight)

And if this number is around 85% or lower, and providing you set the nose-weight correctly, then you shouldn't have any issues towing that caravan.

Kerb-Weight and the 75% Guideline

So what's this? Sounds like the same calculation - and it almost is - years ago the Dutch Caravan Club (NCC) researched the subject of caravan safety and stability, and came up with a similar ratio calculation only this time they used the actual weight of the car and the actual weight of the caravan:

NCC Ratio = 100 x (actual caravan weight) / (actual car weight)

The NCC suggested stability guideline is now 75% or less, it's lower than the 85% recommendation becase the ratio is less favourable in this case.

So why do we mention this? Two very good reasons:

1. The NCC 75% ratio is a measure of the real stability of your car and caravan as you drive it, rather than the extreme limit condition from the 85% guideline.

2. The NCC 75% ratio is used by the WhatTowCar web-site when it advises you on a match - and not the UK calculation - and for this reason alone it's very important to understand the difference.

Power and Torque

Although not too much of a consideration a year or so back, the high price of fuel means that people are looking at more fuel efficient cars with possibly lower power and torque than previous cars.

There is a rule of thumb that says "allow 40 bhp for every 1000kg in the actual weight of your car and caravan" - more is better...

Car Vin Plate

With one exception - the kerb-weight which you can find in the owners manual - all of the important weights are printed on your car VIN plate:

The first weight of 2235kg is the Gross Vehicle Weight for this Ford car.

The second weight 4235kg is the Gross Train Weight - which means that this Ford can tow a caravan up to 2000 kg

The third and fourth weights 1050kg and 1230kg are the front and rear maximum axle loads respectively - and in this case, the sum slightly exceeds the maximum Gross Vehicle Weight - so in this case it is illegal to load the car to both it's axle limits.

Glossary

Mass in Running Order - MiRO - the weight of a car or caravan in a useable state. So in the case of a car, this will include an allowance for the driver, fuel and other fluids. And in the case of a caravan, these will include one gas bottle and spare wheel, but all water and waste tanks must be empty

Maximum Technically Permissible Laden Mass - MTPLM - the maximum weight that a caravan can be loaded to, and this is usually defined by the rating of the axle. For example, in previous years it was possible to order a Triton with either a 1000kg or 1200kg axle.

Car kerb-weight - as defined by the EU (and printed in your UK vehicle V5 document) - this is the car MiRO with a 75kg allowance for the driver, 90% fuel and all other fluids filled.

Gross Vehicle Weight - the legal maximum weight for the car, driver, passengers, fuel and luggage

Gross Train Weight - GTW - the legal maximum weight for the car, caravan, driver, passengers, fuel and their loads

Front Axle Load - the legal maximum weight that the front axle will support

Rear Axle Load - the legal maximum weight that the rear axle will support