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What is a Safe Weight when towing a caravan?

October 16, 2023



What is a Safe Weight when towing a caravan?

At CHECK WEIGHT we have now weighed over 1500 caravan and vehicle combinations.

There’s not much we haven’t seen regarding being legal and being a safe weight.

We have seen combinations that are massively overweight, vehicles overweight and caravans overweight.

However, we get asked all the time – what’s a Safe Weight?

Well, the answer, as with all things in caravan weights, is not that easy.

We will talk about what is a safe weight in regard to the following:

  • Tow vehicle safe weight
  • What’s a caravan safe weight?
  • What is a Gross Combination safe weight?  
  • Vehicle weight versus caravan weight – What’s a safe weight?
  • Tow ball safe weight.

Tow Vehicle Safe Weight

A vehicles weight can be legal, but not safe – and technically it could be illegal and safe (not that we condone this).

Let me explain.

The Gross Vehicle Mass (GVM) of the vehicle is the maximum permissible weight allowed by the manufacturer. Exceeding this could mean a fine, or loss of insurance in the event of an accident.  However, many people overlook the vehicles GAWR (Gross Axle Weight Rating). 

A single vehicle (unhitched) can be under your GVM, but over your GAWR on the front or rear axle of the vehicle.  Front axle ratings are often over when the vehicle has been modified and a lot of extras, ie: weight has been added to the front. A vehicle is seldom over its front axle GAWR when a caravan is hitched to the vehicle, as leverage increases rear axle weight, and decreases front axle weight. 

So, you can be under your GVM – but not safe in a vehicle as there is either too much or too little weight on the front axle of the vehicle.

Conversely, when hitched to a caravan, the tow ball weight adds weight to your rear axle and the front is light, resulting in too little weight on the front axle.

So technically you can be legal, under GVM and at or just under your rear axle GAWR, however it’s not a safe weight as you don’t have enough weight on the front axle, and steering and front wheel braking is compromised.

There is a legal maximum for your front axle, but there is no recommended minimum.   At CHECK WEIGHT we feel like there should be!

Another way a vehicle can be “legal” but unsafe, is by balance. Vehicles we weigh regularly are very unbalanced with as much as 200-250 kg heavier on the passenger side compared to the driver’s side. The passenger’s side is where we tend to put all the heavy stuff – for convenience. Things like batteries, fridges, awnings etc…. An unbalanced vehicle may not cause an accident but may make it harder to recover in an emergency.

What’s a Caravan Safe Weight?

Just because you have a limit – ATM or Aggregate Trailer Mass) doesn’t mean you have to reach the limit. In fact, if you’re at the limit then you’re probably not well balanced having either too much or too little tow ball weight (see below)

Caravan balance is also not a legal requirement – however balance will also affect handling, tyre wear and the ability to recover when things go wrong. At a Caravan show in Newcastle, I had a guy proudly state to me that he increased the tyre pressures on one side of the caravan to the other. When I suggested that maybe he should change the balance by moving weight, he walked away embarrassed by his stupidity.

Caravan balance cannot be ascertained on a weighbridge – they don’t give you that information. Only a mobile caravan weigher with 4 weigh pads, such as CHECK WEIGHT can give you that information.

What is a Gross Combination Safe Weight?  

GCM is exceeded in about 10% of our clients. But if you’re exceeding GCM, you have probably exceeded two or three other weight limits.

A lot of people on Facebook tend to think limits are goals, they are not!

Weight is your enemy (and our friend). Weight increases wear and tear, fuel consumption; compromises braking and acceleration and will wear out your vehicle quicker.

The lower the actual GCM of your combination – the safer you will be.

Vehicle weight versus caravan weight – What’s a Safe Weight?

There is no legal limit saying that your vehicle should be heavier than your caravan – however a lot of engineers suggest that your caravan should be no more than 85-90% of the weight of your vehicle.

We at CHECK WEIGHT recommend that the caravan GTM actual weight should be no more than 90% of the vehicles actual GVM (whilst hitched)

As I said, it not a legal requirement but a recommendation.

If the caravan is heavier than the vehicle than it could “push” the vehicle and may not brake as well.

This scenario ignores the 3500 kg towing capacity (loved by car manufacturers marketing departments) as if your caravans ATM is 3500 and you have a ball weight of say 350 kg then your caravan GTM is 3150.  If you have a GCM of 6000 (eg: DMAX) then the vehicles maximum weight can only be 2850.  Caravan is heavier than vehicle.  Legal but not necessarily a Safe Weight.

Tow Ball Safe Weight

No other question gets the Facebook experts hot under the collar like Tow Ball Weights.

Firstly, there is NO law that says a tow ball weight must be 10% of the GTM or ATM of a caravan. However, it’s a recommendation that we firmly believe should be adhered to.

Generally, we recommend 10-11% of GTM up to 10% of ATM for dual axles and 10-12% of GTM up to 10% of ATM for single axle caravans and camper trailers.

The reason is pretty simple.

The lower the tow ball weight, the more potential there is for the caravan to sway and become unstable and the lower the road speed at which a rig may attempt to change ends – i.e. to jack-knife,)

The higher the tow ball weight – potentially the more stable a caravan may be at a higher speed.  However, a too high tow ball weight – means adding weight to the vehicle and the vehicles rear axle. Potentially making the vehicle unsafe if the vehicle is already fully loaded.

Therefore, knowing all your weights and how they work together is important for towing safely.

We recommend the above percentages as a starting point – but every situation is different, and you need to find the balance that’s correct for you.

CHECK WEIGHT had one client whose tow ball weight was  9% of GTM – when they went on holidays the caravan towed well. However, it swayed on the way home. The owners after receiving CHECK WEIGHT’s unique education program on caravan weight distribution realised that on the way home, they put four wet towels (two adults, two teenagers) wet swimming costumes and all the dirty laundry in the shower at the back of the caravan. This was enough weight to lower the tow ball weight to a point where the caravan swayed.  If you start off with a higher tow ball weight you have more wriggle room.

How do you know your safe weight?

At CHECK WEIGHT we recommend your get weighed by one of CHECK WEIGHT’s four franchise partners, so you’re not guessing.

Know (and understand) your weights. It’s the only way (pun intended) to know that you are both legal and safe.

This blog was researched and written by Jeff DeAth

Jeff has been weighing vehicle and caravan combinations for the last 4 years and is the founder of CHECK WEIGHT – Mobile Caravan Weighing

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