Kerbweight

@cyberyacht Yes, there is an element of that, but in doing so I am trying to dig down into what these numbers really mean and how they are calculated.  My conclusion is that this NCC towing guidance is not fit for purpose and I will follow the legal requirements but ignore this 85% suggestion, which is kind of superstition at worst and rule of thumb at best, marauding as fact.  We should not be misled into buying bigger cars than we need. Rather than upgrading to a more polluting car I can continue using the lighter one.  Its also annoying to me that other "safe matching" tools use this 85% suggestion in their analysis of how safe your outfit is.  "Kerbweight" is useless as a definition, the forces of physics do not care if the mass of the vehicle pulling is composed of cast iron engines, human beings or tanks of water. Weight is weight as someone else said, the only issue is to make sure it is properly distributed, but it should not be ignored.  To say kerbweight is only ever calculated as the car and driver, when it could be 300kg heavier with passengers, luggage and whatever else, is ridiculous.  This is why there is such a big gap between the legal limits and the limits imposed by the 85% suggestion. My legal towing limit is 1800kg, but as its mass in service is only 1,548 then using this 85% rule would give only allow a MTPLM of 1,315.  That's an enormous difference.  The key is to know how much weight is in your car, how much in the caravan, and stay within legal limits.  I would have hoped that over a 30 year period the NCC advice could have kept up with advances in technology (cars are delivering more power for less weight) and innovations like twin axle, etc instead of remaining unchanged as it is becoming irrelevant.  It doesn't say a lot about the industry that they can't sort this out and at least use the same definitions as are used in the V5 and VIN plate instead of vagaries like 'kerbweight'.

"...then using this 85% rule would give only allow a MTPLM of 1,315."

which sounds sensible to me for the car in question.

Superstition.  The car has been tested to within an inch of its life dragging 1,800kg around the french alps for 3 weeks.  that's how it got a legal braked towing limit of 1,800kg.  so how can 1315kg possibly be reasonable?

You just don’t get it, do you?

I hope your exaggeration never comes back to bite you.

Does any of this really matter. Each vehicle has a max towing limit as designated by the manufacturer. This might be anything from about 40% in the case of electric vehicles to 150%+ for some 4wd.

It does not matter a hoot how you define kerb weight, if you exceed the manufactures maximum then you are towing illegally.

Colin

Bear in mind that the picture can also be the other way round. Some cars have a maximum permissible towload that is less than 85% of their kerbweight.

Whether an outfit is safe or not depends more on the ability, due care and attention of the driver than a weight ratio.

Regarding stability and weights I always consider the difference in safety between carrying  a 25 kg bag of sand and a 25kg sheet of ply in heavy wind. Weight might be weight but only one of them is likely send you to your death over a cliff.

With due respect if you are happy to bat away & argue against every attempt to help why not just do your thing the way you see it & enjoy👍🏻

If you drive in an appropriate manner and adjust your driving to suit the conditions, towing sheets of plywood can be just as safe as towing bags of sand.

Lutz, to give an extreme example, do you think an empty low loader car transporter at 1200kg would not be a safer tow than a 1200kg 2.5m high empty box trailer.

The shape/profile has to enter into the equation. 

Colin