Tow car and caravan matching advice

[Dogjen]

Just getting ready to return to caravaning after a long absence. We changed our car to a VW Passat 2.0 Diesel Estate in anticipation then placed an order for a Sprite Major 4 EB. I did check on one of the matching sites which said it was a good match however checking another recently showed it was over 90%.
Checking in to it in more detail my car has an unladen weight of 1541kg (includes 90% fuel, driver at 68kg and 7kg luggage) and the caravan MTPL is 1433kg which gives a ratio of 93%. I know this is still acceptable however my thoughts are -
My car will always have the two of us in it when towing so our combined weight of 162kg added to the car weight will be 1628kg, I religiously weigh everything before it goes in the caravan so assuming we have a total of 150kg of possessions and I split that equally between the car and caravan so my car weight is now 1703kg. My caravan MIRO is 1232kg with the added 75kg for possessions will be 1307kg. This gives a ratio of 77%. So I am assuming with careful weight distribution I can achieve a good match with the caravan and car. Would I be correct in my assumption? though reading a lot of the comments on the forum I will be to busy going over my caravan looking for quality/build issues.

 

[ProfJohnL]

Just getting ready to return to caravaning after a long absence. We changed our car to a VW Passat 2.0 Diesel Estate in anticipation then placed an order for a Sprite Major 4 EB. I did check on one of the matching sites which said it was a good match however checking another recently showed it was over 90%.
Checking in to it in more detail my car has an unladen weight of 1541kg (includes 90% fuel, driver at 68kg and 7kg luggage) and the caravan MTPL is 1433kg which gives a ratio of 93%. I know this is still acceptable however my thoughts are -
My car will always have the two of us in it when towing so our combined weight of 162kg added to the car weight will be 1628kg, I religiously weigh everything before it goes in the caravan so assuming we have a total of 150kg of possessions and I split that equally between the car and caravan so my car weight is now 1703kg. My caravan MIRO is 1232kg with the added 75kg for possessions will be 1307kg. This gives a ratio of 77%. So I am assuming with careful weight distribution I can achieve a good match with the caravan and car. Would I be correct in my assumption? though reading a lot of the comments on the forum I will be to busy going over my caravan looking for quality/build issues.

The towing ratio advice is just that ADVICE, its not a statutory requirement so don't focus to much on it. Having said that it is always best to keep the weight of a trailer as small as possible, but its of probably greater importance to get the loading of the caravan right to achieve a sensible nose load, and for the driver not to do anything silly.

No regards the towing ratio, it is a fictitious figure and it is always the calculated worst case scenario where the unladen weight of the car vs the MAM of the caravan. In practice no outfit is likely to ever match its towing ratio., changing how you load the car and caravan does not change the "official" towing ratio. But it is sensible to preferentially load the car than the caravan.

 

[Raywood]

Personally I prefer to try and keep the towing ratio to 90% or less but many people do tow successfully above that. It is for the experienced only though.
I would make sure that you pack some weight in the car but do not overload the back axle doing it. The Passat is a good tow car, my neighbour had one and had no problems although it towed a lighter caravan.
The ratio is based on the kerb weight of the car and includes 75kg for the driver although I am not sure if VW include this in their figures.

 

[Hutch]

I like to tow our caravan heavier than lighter, this is due to , not being so easily blown about in winds or when overtaking HGV's or visa versa. But of course watch out for that dreaded Nose weight on the tow bar. The car is normally heavy being two of us, two dogs and a coolbox of Wine beer and a 10 kg box of dog food.
Happy touring to all this summer.

 

[Raywood]

Heavier caravans should in theory be less prone to problems with sidewinds but other things do come into play so it is not the full story nor should it be used as a basis for using a tow car that is too light. The problem is that if you do get snaking the higher the towing ratio the more chance there is of the caravan taking control with the inevitable result. Some cars are better at controlling snaking than others but the better the towing ratio the safer the outfit.
I am not aware of any studies on how more weights affects resistance to side winds so I would not rely on it.

 

[ProfJohnL]

Heavier caravans should in theory be less prone to problems with sidewinds but other things do come into play so it is not the full story nor should it be used as a basis for using a tow car that is too light. The problem is that if you do get snaking the higher the towing ratio the more chance there is of the caravan taking control with the inevitable result. Some cars are better at controlling snaking than others but the better the towing ratio the safer the outfit.
I am not aware of any studies on how more weights affects resistance to side winds so I would not rely on it.

The stability of an outfit is affected by the towing ratio, and id I still maintain you should aim to keep the trailer as light as possible, but I'd venture to suggest that the quality of a tow is more down to the correct load distribution inside the caravan than its actual weight.

It doesn't require any studies to prove that the heavier a caravan is, the more resistance it will have to side winds. Windage creates a thrust, or a force on the side of a caravan, and it will try to accelerate it sideways, but caravans have mass which resists acceleration. its a very simple Newtonian equation:

Force divided by mass = Acceleration.

So the bigger the mass the smaller the resulting acceleration.
Simples

 

[Raywood]

Hi Prof, I think that you basically agree with my summary. What I was trying to say is that it is not clear how great the reduction in wind disturbance is as the weight increases so I would not rely on it. I have to say that our Lunar is less affected by wind t5han the previous Avondale model despite being a bit lighter. I think it is more down to design rather than weight distribution, although the different layout might affect the balance.

 

[ProfJohnL]

Hi Prof, I think that you basically agree with my summary. What I was trying to say is that it is not clear how great the reduction in wind disturbance is as the weight increases so I would not rely on it. I have to say that our Lunar is less affected by wind t5han the previous Avondale model despite being a bit lighter. I think it is more down to design rather than weight distribution, although the different layout might affect the balance.

Too True

 

[camel]

If a towing vehicles engine/torque/psi is capable of towing a caravan without any problem but the caravan weighs more than the towing vehicle when fully laden what is the problem taking into account that the towball weight is not exceeded, if you take for example an articulated LGV plated at 44 ton and the vehicle tares off at 17.5 ton that gives a pay load of 27 ton, the tractor unit alone weighing around give or take 8 ton which means that the weight behind the tractor unit on he trailer is far greater but because the trailer is braked all is fine, surely this would apply to a car/ caravan outfit because when ever the car is braking the caravans brakes will be activated, which makes sense of what the Prof says that the 85% is just a guide line and something just picked out of thin air some thirty odd years ago,

 

[WoodlandsCamper]

And how often do lorries jack knife under severe braking?? You cannot compare cars with lorries due to the fundamentally different pivot geometry.

 

[camel]

And how often do lorries jack knife under severe braking?? You cannot compare cars with lorries due to the fundamentally different pivot geometry.

Woodlands camper , Under sever braking the ABS will come in on the trailer which is fitted to the middle axle on the trailer very straight forward, the only time a jack knife happens is in appropriate driving, very similar to what the caravan industry are now catching up on, over the years I have seen more caravans wrapped round the M5 than LGV's,

 

[seth1]

As previously said you cant really compare an HGV to a car and caravan.The point of articulation is in a different place for a start.Also the king pin load when coupled to a trailer places loads on the front axle,slightly opposite to a car/caravan combo.Although i do agree HGV,s are far safer regarding braking.

 

[Raywood]

Articulated lorries did have a problem with jacknifing under breaking at one time. They are now generally fitted with a device on the fifth wheel that inhibits this and has improved the situation considerably. They are not however comparable with caravan towing. You will see that where lorries tow a conventional trailer the two are far more balanced.

 

[ProfJohnL]

... You will see that where lorries tow a conventional trailer the two are far more balanced.

Hello Ray can you explain this comment please?

 

[camel]

I think Ray is referring to a 'Close couple coupling' rather than a fifth wheel coupling,

 

[Raywood]

... You will see that where lorries tow a conventional trailer the two are far more balanced.

Hello Ray can you explain this comment please?

In general when a conventional lorry tows a trailer, known as a drawbar combination, the trailer will generally be a lot lighter than the towing vehicle and its load. You are very unlikely to get a trailer and its load heavier than the towing vehicle although it can happen. They often have other features like a system that can move the trailer closer to the towing vehicle with an arrangement that moves it back again on tight corners and the brakes are activated by the lorry rather than the overrun ones on a caravan. Most have a wheel at each corner which aids stability although there are central twin axle arrangements with additional features to balance the load..

 

[SamandRose]

From our experience of towing with the Passat (which isn't extensive but does include towing a 1250kg caravan through France to Switzerland and back) the car should cope OK. If you're worried about the weight ratio try taking the caravan lightly loaded for a few weekends away to get used to how it handles before loading it up more heavily for a longer trip.