Caravaning

Weight Issues

So last time I shared the specs of the weights of the caravan.  Weight and caravans is an important thing.  Caravan organisations recommend keeping the caravan as less than 85% of the tow car's weight. Otherwise you are more likely to have the caravan cause control or stability issues to the tow car.

3 weights are given. Mass in running order (MRO) which is the weight of the caravan, without anything extra. Basically what you would expect it to weigh when towing it from the showroom on the day you bought it.
Payload is the amount you are allowed to load into the van before it is considered overloaded.
Maximum Technically Permitted Laden Mass (MTPLM) is how heavy you are allowed to make the caravan by adding things to it.  It is the sum of its MIRO with user payload.

So with these numbers in mind, and using the 85% guideline, an ideal weight for a tow car would be around about 1700kg.

And this is the next thing that made life potentially difficult. Driving licenses.

Hannah and I both passed our tests after the changes in 1997, which then no longer automatically gave people in UK the license to drive 17 seater minibuses, 7.5T trucks or a car and trailer that have a combined "train weight" (that is the sum of car and caravan weights) of over 3.5T. 

According to the government:

Licences issued from 1 January 1997

If you passed your car driving test on or after 1 January 1997 you can:

• drive a car or van up to 3,500kg maximum authorised mass (MAM) towing a trailer of up to 750kg MAM

• tow a trailer over 750kg MAM as long as the combined MAM of the trailer and towing vehicle is no more than 3,500kg

Here comes the next number. MAM.  That is the maximum weight that a vehicle can weigh.  The same as the MTPLM of the caravan.  But here is the snag. It isn't what the car / caravan combination currently weigh, but what the maximum the could weigh.

Long story short, Hannah and I both had to go and take a car + trailer (B + E) test.

We used a driving schools car, as our tow car is an auto, and the other catch that there is with licenses is with a normal B license, if you take a B + E test in an auto, you are only allowed to tow a train weigh of over 3.5 T in an auto!

So how were we certain of this?

First off, the car weight plate, which is often just inside the door, and includes the VIN too:

so the 4 numbers above are:

• 2320 kg: Maximum Vehicle weight (MAM)
• 4825 kg: Maximum Train weight
• 1190 kg: Front Axle weight
• 1180 kg: Rear Axle weight

It is the 2nd number that is important for towing. This number minus the MAM gives the maximum towing weight, so for the above example, 4825 - 2320 is 2505 KG. 

Next, the caravan weight plate:

Its a bit more simple than the car, it calls things what they are.  MRO, MTPLM, no calculations!

But taking the details from the 2 above images, it means our caravan rated at a max of 1459 kg is fine to be towed, but it does show why we needed the B + E license, our combined max train weight could reach 3779 kg

The next thing to consider is nose weight.  The car chassis and tow mount are rated to take a certain amount of static downward weight.  I imagine this is to reduce weight transfer from the front axle to the rear axle as well as controllability of the car and caravan.  Certainly when I was doing my training, I noticed in the damp how the front wheel drive car was more prone to wheel spin, especially when turning or going up a hill.

One rule of thumb I've seen is to aim for a nose weight of between 5% and 7% of the MTPLM of your 'van, assuming this doesn't exceed your towball limits.  5-7% of 1459 kg is 73-102 kg.  Our tow ball limit is 100kg, so I aim for about 85kg to give some room for measuring tolerances and to avoid going over the limit.

But when trying to load or adjust the nose weight, please, don't just put all the load at the front or the back to adjust it.  This little video shows nicely how moving weight forwards or backwards