Towing weight, Which is legally correct?

This has been discussed a few times before and taking the forces in the time honoured mechanics methods in two perpendicular directions the engine does the 'towing' and so 'tows' all the extra weight horizontally. So I'm in the car tows all the weight camp. 

Before the tests were scarped if you didn't have a towing test you could tow only a certain weight, I forget what it was (was it 1500Kg?) but it simply said that, towing a certain weight of caravan. It didn't mention having some of that weight 'transferred' to the car and so as you say you couldn't have I'm towing a caravan of 1560 kg as I have 60Kg of that on the hitch as a defence when pulled over?   Do Weighbridges weigh the caravan by themselves or hitched up? 

Also it would be too difficult to work out what you could tow with your car?

All the laws here just state a weight of a trailer/caravan, I can't see any mention of some of that being on the hitch?

If stopped and checked I wouldn't like to explain the weight in that way?

A bit of a interesting discussion but I would think most people would just go with the weight of the caravan?

I think if push came to shove the GTW of the car, the MAM of the car and the MTPLM of the van would be the weights the authorities would be looking at, ie option a.

The gross vehicle weight of the car includes the noseweight, but so does the MTPLM of the caravan. Therefore you can't add the two together or else you would be counting the noseweight twice. Consequently the towed weight is the axle load of the caravan only, not its total weight. The noseweight is carried, not towed, by the towing vehicle.

Consequently, neither option a) nor option b) are correct.

Per definition, this is how the sums add up:

GTW 3500kg - MAM 2000kg (this includes the 80kg noseweight) = 1500kg towed weight

but

MTPLM of the caravan = 1500kg towed weight + 80 kg noseweight = 1580kg

That is how towed weight is defined in the regulations.

Actually, the allowable towed weight could even be more than 1500kg so long as the plated MTPLM is not exceeded, but then the MAM of 2000kg cannot be used to the full or else the GTW would be exceeded. 

Thank you Lutz, so you couldn't subtract the nose weight from the MTPLM to get within the cars limit.

For example juggling the figures a bit the car manufacturers towing limit is now1450Kg van MTPLM 1500Kg minus 80Kg nose weight= 1420Kg. 

Presumably the towed mass is still 1500kg as seen by the cars towing capability and towbar attachment points etc?

We've had this before (about what is 'towed') and I disagree, mathematically it doesn't make sense but no point in going over old ground. For me 'towing' is the forward force on the tow bar or that made by the engine to pull the caravan forward otherwise all the A level exams and university exam paper questions make no sense when asking to find it? If the caravan wasn't there that extra towing force wouldn't be either. But no use starting that again. The MTPLM is the MTPLM, it doesn't matter how it is distributed vertically. Reply if you wish telling me I'm wrong but I'll keep to that view as that is what I was taught and experiments confirm it.

This is Uk law you're talking about btw?

I wish anyone arguing the view put forward by Lutz with the Police/VOSA the very best of luck. I'd not want to be that person.

I don’t know what is so difficult. The car is not towing the full mass (weight) of the caravan, but only its axle load. The rest, I.e. the noseweight, is being carried, not towed. That’s why the noseweight counts as payload towards the overall weight of the car. Anything else and the sums wouldn’t add up.

If you want to read it in the regulations it’s all in Article 2 (Definitions), Paragraph 9, of 1230/2012/EU, as referenced in UK road vehicle legislation.

I agree with Corners ... 

I am getting a little confused I have always veered on the side of caution.

We tow a 2016 Swift Conqueror 480 the manufacture MTPLM was 1454kg, as we towed with a Ford Kuga at the time we upgraded to 1550kg, however changed to a Mitsubishi Outlander PHEV with a permissible towing weight of 1500kg and a maximum nose weight of 75kg.

We went back to our supplying Swift dealer and had the MTPLM downgraded to 1500kg, I assumed if the outfit if measured on a weighbridge is should be 1500kg or less including the nose weight on the hitch/jockey wheel or am I missing something ?

Yes, a 1500kg MTPLM would include the noseweight, but the car would only be pulling 1500 minus 75kg = 1425kg. On the other hand don't forget that when hitched to the caravan the car would weigh 75kg more.

If anyone interprets the law any differently, it's up to them, but the law is actually quite clear that the car is only pulling the axle load of the caravan.

One should not fall into the trap that MAM + MTPLM = GTW.

Mobile weight checks are normally carried out without unhitching the caravan. That means that only the axle load of the caravan will be measured, not the MTPLM. To check whether the MTPLM is exceeded or not, one would have to unhitch and put the caravan on its own, including the jockey wheel, on the weighbridge.