Another MAM/towing limits question...GTW Vs MAM

[goofygol]

Hi, I did search the forum to see if this had already been answered, but my particular variant of this query hasn't! I've just joined because after scouring about 10 different sources + gov website, it's still not clear to me what is legal, so i thought i'd ask the experts on here.
I passed my test after 1997, and i'm aware that I should have B+E automatically added to my licence. What isn't clear to me at all is whether the 3500kg limit is Just the MAM Of the trailer, or the Trailer + Car combined MAM, or in other words, the Gross train weight.

I'm not towing a caravan...it's a car trailer. The trailer has an MAM of 2000kg, according to the chassis VIN plate.
On my car's VIN sticker, it's MAM is 2075kg, and the number underneath is 3850kg, which i assume is the gross train weight. I know my car has a towing capacity of 1700kg, this is in the manual + on the V5. The additional 75kg must be the towball downweight which is added on to give 1775kg (3850 - 2075).

Therefore, my total MAM of car and trailer is 2000 + 2075 = 4075kg. Either:
- it's illegal, because the limit is 3500kg combined, or
- it's illegal, because i'm above my car's stated gross train weight, 4075kg VS 3850kg.
- i'm legal, because my actual weight of trailer+load combined is well short of it's 2000kg MAM (more like 1300kg), and therefore 1300+2075 = 3375kg which is < 3850kg.
- i'm legal, because my actual weight of trailer+load is ~1300kg, and my actual car +load will be also no where near it's 2075kg limit, and more like 1800kg, and therefore 1800 + 1300 = 3100kg, which again is well short of the 3850kg GTW.

or i'm still wrong somewhere?!
i need to clarify all this because i want to buy a cheap 2nd car purely for towing and so the choice may depend on how the legislation applies...

 

[RogerL]

The 3500 kg limit applies to the trailer - but subject to it's own maximum weight (2000 kg in your case) AND subject to the car's maximum towing weight (1775 kg in your case)

HOWEVER if the trailer isn't fully loaded it may still come within the 1775 kg and be legal

In addition if the car isn't fully loaded then then as long as the sum of the actual laden weights don't exceed 3850 kg then that would be legal too.

 

[ProfJohnL]

Unfortunately you have chosen a topic which is rather complicated. I hope the following may be helpfull.

You have to approach this topic from two directions. the first is as a driver which is defined by your licence entitlements - which tells you what you are allowed to drive. Then secondly from the tow vehicles perspective which determines what the vehicle is legally allowed to tow.

From your licences perspective, it tells you the maximum masses (=maximum Weights) of tow vehicle and trailer you are entitled to drive. These are absolute limits with no upward tolerances,

In practice with a post 1997 licence (it is different for licences issued before 1997) you can drive any normal domestic car, provided its Maximum Authorised Mass (MAM = GVM) does not exceed 3500kg (or 4250kg where an unbraked trailer not exceeding 750kg is used) . That encompasses all normal domestic cars.

With the now assumed BE licence you are also allowed to drive a a towed outfit of combined MAM not exceeding 7000kg . There is no tolerance on the upper commuted figure even a 1Kg over 7000 top limit and it is clearly illegal . The values used are vehicle specific and derived from the VIN plate data on the vehicles, so its a paper exercise to establish if you are complaint or not. If you are non compliant the offence is driving without a licence.

From the tow vehicles perspective, you are legally obliged to conform to the mass limits defined on the vehicles data plates. The Tow vehicles VIN plate carries four load limits,

1. The solo vehicles MAM in kg (Gross Vehicle Mass)
2. The tow vehicles and trailers combined MAM in Kg (Gross Train Mass)
3. The tow vehicles front axle maximum load limit
4. The tow vehicles rear axle maximum load limit

Vehicles with a tow bar fitted will also have another data plate on the towbar which defines the maximum permitted static vertical trailer nose load, ("S" value) and the maximum mass of the trailer that can be towed. Strictly the towed mass is only the load on the trailers road wheels. it ignores the vertical load of on the coupling. The towed load is not the MAM (or MTPLM) of the trailer.

Modern trailers should also have their own VIN plates near the front of the trailer which define the Trailers MAM (Also known as MTPLM) This is the maximum permitted mass/weight of the entire uncoupled trailer - including the nose load at the coupling couplings "S" value

It will also list the maximum permitted load each of the road axles

It should also also list the maximum "S" value which is the static vertical vertical nose load you may trim the trailer to create.

At no time solo or coupled should any of these limits be exceeded. For a specific examples. The tow vehicles combined maximum axle limits may exceed the vehicles stated MAM - this means you cannot load both axles to their maximum value at the same time, one or both must be reduced to bring the whole vehicle mass in line with the MAM limit. Also you may a difference in the tow vehicle and the trailers "S" values. You must always consider the lowest "S" value to be the working limit.

Most tow vehicles specify a maximum towed mass it can successfully pull, legally the towed mass is only the load supported by the trailers road wheels - the nose load arising at the coupling is supported by the towbar and thus is carried by the tow vehicle, and must be accounted as part of the load in the tow vehicle. As this value varies depending on how the trailer is loaded, it cannot be assumed to have a known value unless it is specifically measured.

The UK and UE regulations assume every trailer will be loaded to produce a minimum nose load value of 25Kg or 4% of its load mass. and for simplicity UK caravan organisations recommend aiming for between 5 and 7% of the trailers MTPLM provided that does not exceed the tow vehicles tow bar "S" value.

Just being legally and technically compliant is no guarantee of safety. it requires sensible attention to the maintenance of all vehicles, and good driving habits.

I recommend checking you have a good match of tow vehicle and trailer that offers reasonable margins of capacity. It is sensible to choose a tow vehicle and trailer where the trailers MTPLM does not exceed the tow vehicles stated maximum towed weight limit

 

[goofygol]

so from what you've both said, basically, it sounds like the Actual values are what matters, not theoretical. My worry was, PC plod would stop me, add up the MAM of my car and trailer together, and go "this is illegal because your total MAM is greater than your car's GTW limit". (4075kg VS 3850kg)

In reality, i'm operating well under the MAM limits of both car and trailer individually, and when added together give a combined weight of around 3100kg which is well below the car's 3850kg limit.
Therefore it's all good - my 4th option in the original post is the right one.
phew.

it's a shame that gov.uk doesn't actually explain it properly at all, other than to say in the drivers licences section that B+E = 3500 + 3500.
There's no detail anywhere on the section on towing and limits about how the legislation is applied when it comes to vehicle limits. Presumably this is embedded somewhere else and that there's some sentences around complying with the car's specified gross train weight/towing capacity, which to be fair, is listed on the V5 document.