It is true that there is no written law applying to the 10% rule of thumb and lightweight Euro vans have much less TB load and tow quite well. However, be careful because, as in the case of the Ranger, the vehicle manufacturer has placarded the vehicle with a minimum of 10% TB load and therefore using that vehicle it does become a requirement and you could get done for not meeting that requirement, particularly in the case of an investigation into an accident you maybe involved in. So know your vehicle and your van weights and stay within those boundaries.

 

The following are 2 extracts, one from  Collyn Rivers (yes I do admire him Yobarr) and Allan Whiting

By Collyn Rivers   https://www.gorv.com.au/caravan-weight-myths/

Myth 2: For optimum stability, all caravans need about 10% tow ball mass.

Reality: Desirable tow ball mass is more an issue of where mass is along that caravan. That 10% is easily remembered and generally adequate. A short centre-heavy caravan, however, needs far less than does a long end-heavy caravan. Camper trailers prove this. Most are a mere four metres, yet some weigh close to two tonnes. Almost all are ultra-stable; however, their recommended tow ball mass varies from 3% to an extraordinary 20%.     (note he doesnt include "extraordinary" with 3%)

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The following is an extract from Allan Whiting - Allan Whiting was trained by Volvo Trucks in the 1970s as a military vehicle demonstration driver and for many years was a qualified 4WD instructor. Allan is widely known for his past role as 4X4 Australia Magazines Technical Editor of 15 years.

 

https://outbacktravelaustralia.com.au/driving-towing-towing/towball-weight-and-trailer-stability/

 

Why do the Aussies and Yanks insist on 10-15-percent towball weight, while the Europeans are content with around six percent? Towing speed is the main reason for the difference and that makes the Australian practice something of a misfit.

 

 The purpose of this percentage is manifold: guaranteeing that the trailer wont lift the rear wheels of the towing vehicle under acceleration or when climbing a steep grade; ensuring that the trailer tracks accurately behind the towing vehicle; and preventing trailer sway.

In North America virtually all trailer and caravan makers endorse the 10-percent rule and some go so far as to suggest the towball load should be as high as 15 percent. In the case of a 2000kg trailer that means a towball load of 200kg to 300kg.

In Europe its an entirely different story: the typical EEC car and 4WD towball load is between 50kg and 75kg, and even heavy trailers above 3500kg  have towball loads around 100kg.  (that might account for the rollovers in UK not the lightweight vans)

Why the difference, given that trailers and towing vehicles are pretty much global vehicles these days?

 

The North American scene

Published research on the ball weight topic is very hard to find, but weve managed to dig up some US calculations and real-world testing done in 2008 by Delphi and published by the SAE. These findings explain why the Yanks get lower trailer-towing ratings for globally available vehicles and why they insist on 10-15-percent ball weight.

If you buy a Toyota or Subaru, for example, in the USA youll find that the trailer rating is much lower than it is in Europe or in Australia around half and the reason is mostly to do with road speed.

Towing speed limits differ across the USA, but vehicle and trailer designers must assume the highest legal speed is their target and that is between 65mph and 80mph (105km/h and 130km/h). Thats faster than trailer towing in any other country, which is why American-market towing vehicles have conservative towing ratings.

Also, as the Delphi study showed, heavier towball weights are necessary at 130km/h and above.

The Delphi study looked at variables, including the centre of mass, axle placement and vehicle speed, and calculated if the trailer was likely to sway. The predictions also noted and at what speed it was a decaying oscillation (taking care of itself) or an exponential oscillation (building to an accident).

 

Firstly, they assessed the stability of the tow vehicle, described by a dampening ratio, which when positive meant stability (decaying oscillations) and a negative damping ratio meant the opposite.

Up to 100mph (160km/h) and beyond, the tow vehicle had a damping ratio ranging from 1-0.5 quite stable.

With a trailer in tow the tow vehicles damping ratio actually improved, but the trailer showed a damping ratio that ranged from 0.3 at 37mph (60km/h) and crossed into the negative at 71mph (112km/h).

This mathematical model was followed by a real word confirmation study with an adjustable trailer that tested three different configurations at different speeds.

In the first configuration the centre of mass was forward of the axles and the tongue weight was 10 percent. In the second configuration the centre of mass was moved rearwards, but still in front of the axles with the tongue weight at three percent. In the final configuration they put the centre of mass behind the axle line, giving a negative 10-percent ball weight.

In the first example, the truck and trailer remained stable up to and beyond 100mph (160km/h).

In the second example the truck and trailer crossed the stability threshold at 65mph (105km/h). (thats at 3%)

In the third example the truck and trailer crossed the stability threshold at 45mph (72km/h).

Note that the second example, with only three-percent towball weight was stable up to 105km/h.  (Ive previously mentioned this)

 

Australia USA towball weight at EEC speeds

Australia has largely adopted the North American model. Most trailer and caravan makers endorse the 10 percent rule, regardless of the trailer configuration and the number of axles.

Many car and 4WD makers hate the 10-percent rule, because it forces them to design heavier rear sections and stiffer rear suspensions than they need in most markets. (so now they are talking proper 4X4)

Why have a heavy towball weight in the first place, many people ask?

 

The marketplace is full of theories, but very light on actual test results. As the above US research shows, a heavy towball load reduces the chance of trailer sway at very high towing speeds.

However, EEC trailer regulations mandate lighter towball loads, because European caravans mix it with high-speed traffic on multi-lane roads theyre restricted to 100km/h and 80km/h on secondary roads. (Previously mentioned thankyou)

European and Australian light and heavy truck pig trailers drawbar trailers with centrally positioned tandem or tri-axle bogies that are restricted to 100km/h have very little or no towball weight and dont have significant sway problems.

Eg vehicle manufacturers analysis and Society of Automotive Engineers testing has shown the factors that influence trailer sway include driver skill, speed, vehicle and trailer weight, vehicle and trailer load centres of gravity, number of trailer axles, aerodynamics, heavy-vehicle air turbulence, weather conditions, road surface undulations, wheel bearing condition, trailer brake adjustment, towball to coupling clearances and friction, tyre pressures and the suspension dynamics of towing vehicle and trailer.  (so a blanket 10% rule is not appropriate for many as there are many other factors)

The prospect of negating all these factors by simply upping the towball weight is unlikely. (Big call and my side of the debate)

Interestingly, on the subject of driver skill, the EEC trailer towing regulations limit car-licence drivers to 750kg trailers, with or without brakes. To tow a trailer weighing 750kg up to 1750kg requires two days of driver training and an upgraded licence test. (mentioned previously but largely not talking about over 2000kg which can be lowered to 1750kg as 2000kg was just plucked out of the air to be lightweight)

Towing trailers that weigh more than 1750kg requires a truck licence. Can you imagine our weak-kneed pollies implementing such repressive legislation?

European police regularly spot-check trailers for roadworthiness, gross mass violations and excess towball loading. All cars or 4WDs towing trailers above 80km/h, up to a maximum of 100km/h in Germany, must have a friction-type coupling to reduce the likelihood of trailer sway.  (Another good addition however friction hitches lose their effectiveness at around 100kph)

Additionally, North American and European vehicle makers are increasingly turning to electronic stability control (ESC) to counter trailer instability. Bosch, AL-KO and Dexter have introduced ESC systems Down Under.  (ESC could be incorporated into lightweight vans as a mandatory requirement. My Jurgens have ESC and friction hitch)

As with solo-vehicle ESC the system applies selective wheel braking to towing vehicle and trailer, to prevent a pendulum effect developing. Trailer ESC is activated when the trailer plug is connected to the towing vehicle.

Weve driven a 42-tonne EEC-spec prime mover and trailer combination fitted with ESC on all axles and found the stability improvement almost unbelievable, but European truck makers stress the point that ESC wont make up for a poorly loaded or badly driven combination.

 

2009 there was virtually nothing published in Europe on the topic of real-world, light vehicle and trailer towing stability, although its known that some vehicle makers have done considerable R&D in this area. In contrast, heavy truck and trailer R&D is well documented and all prime movers and semi-trailers sold in Europe can be ordered with stability control.

A paper entitled An experimental investigation of car-trailer high-speed stability was published in mid-2009 by the Department of Mechanical Engineering at Bath University in the UK.

The paper, by J Darling, D Tilley and B Gao, summarises the findings of tests carried out on a standard UK-built caravan and on an adjustable trailer, in which different dimensional and mass factors could be evaluated.

The tests began with matching the adjustable trailer so that it replicated the dynamic behaviour of the caravan, then altering one dimension change and one mass change at a time, to evaluate the results of the changes. More than 600 different trailer parameters were examined.

In summary, the engineers discovered that the three most significant parameters affecting trailer stability were trailer yaw inertia, nose mass and trailer axle position. Interestingly, the total weight of the trailer wasnt a stability issue of itself, but weight distribution was critical.

 

________________________________________________________________________________________________________________________

 

So, sorry it couldnt be shortened further. To Clarify-

 

Based on the above information let us fix the description in this thread that a lightweight caravan means less than 1750kg ATM as research is based on that

That based on 3% towball weight the speed of the rig should not exceed 105kph but 5%, or 6,7,8 would be above that speed. Given 160kph was stable with 10% TBW there is a lot of adjustment here.

 

Clearly we need the authorities to consider this topic. More so we need the caravan community to readjust their blanket 10% "rule" and be more accommodating to lightweight caravans for their differences in all the areas mentioned and underlined.

 

Thankyou Ralph. 

 

Much appreciated.

yobarr wrote:

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Are We Lost wrote:

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Ben Taxyl wrote:

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My original post was about the 10 per cent rule not being acknowledged by vehicle manufacturers.

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 Some do. This snippet is from my 2018 Ford Ranger owners' manual.

So the design engineers for one of the more capable tow vehicles in that market believe that less than 10% is unsafe. I know it's a "one size fits all" situation, which is not ideal, but I assume that is because it keeps things simple.

---

 Thanks Stephen, for posting this. Had Ben taken my advice to research how tow ratings are issued he may not be as confused as he appears to be.

I did not say that he is confused about his vehicle, as the figures are as he posted, but the fact that max towball weight is listed as 200kg DOES NOT mean that that vehicle has ANY chance of safely towing 3200kg as a PIG trailer.
We can only help those who are receptive to being helped. Cheers.

---

 "We can only help those who are receptive to being helped." How nice! My post was again, more about manufacturers ideas about towball loads. I am not and don't need to ask for advice on the subject and I find your responce to be quite rude. I'll bet you would not speak to your friends in that manner but seem quite happy to abuse a total stranger. If my comments and input don't meet your fanatical needs then suck it up princess. I'm not going away!

Ben.

No Possum Such an officer would need to have towing knowledge, experience and data. And compete with evidence I've posted above that is written proof by experts that, endorse what I'm suggesting. Law also trumps opinion. Are you really suggesting that a lightweight caravan, any caravan that is involved in an accident that had 5% towball weight the driver could be charged with an offence when there is no regulation that covers towball weight?  If thats the case (and I stand corrected) "careless driving" is the only offence that comes to mind. Do you know the difficulty in proving careless driving, its the offence police often only enforce  when they have 110% proof.  5% TBW is not illegal Possum, in fact it is very legal. Good luck with that one. A magistrate would throw it out of court.  However I do appreciate your input as I too have observed your input on the forum and thankyou for that.

 

So to assess this thread now there is only one possibly valid arguement for less than 10% TBW and that is speed however as we can only travel 100kph and so far the evidence I've produced is 3% at 105kph is the maximum you should tow then 5%+ has zero concern. It could be taken into account as would be ESC and friction hitches but to date there is no other reason lightweight vans should adhere to 10%. Such topics should be discussed freely and without fear one is going to "upset the apple cart" with owners of heavy vans in tunnel vision

 

Thanks for your contributions.

-- Edited by Eaglemax on Wednesday 23rd of August 2023 09:37:33 AM

-- Edited by Eaglemax on Wednesday 23rd of August 2023 09:43:45 AM

-- Edited by Eaglemax on Wednesday 23rd of August 2023 09:46:55 AM

Gundog wrote:

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How do I work out my towball weight very simple actual ATM - GTM = TBW, its not rocket science, and that is with the WDH engaged which is a requirement when towing ove 1800kg.

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 Interesting thoughts! Could I respectfully point out that it is impossible to determine TBW when the van is on the car's towbar, let alone when a WDH is engaged. A WDH does NOT change towball weight, but it does change weight on van's wheels. (GTM)

The only definites when a van is hooked up to the car are the axle weights, although it is possible to calculate an approximate towball weight by taking rear axle weights before and after hooking up to the van.

Your calculation ATM-GTM=TBW gives allowable towball weight, nothing more. Cheers

 

Again I have to disagree with those that claim tow ball weight does is not changed by using a WDH. Towball weight is easily determined on a weigh bridge as weight of hitched vehicle minus weight of unhitched vehicle, and this is independent of whether a WDH is in place or not.

Why this is so is because the weight of the vehicle itself is constant. It is determined by its mass and the acceleration due to gravity, neither of which are altered by a WDH.

As Yobarr keeps saying, simple physics.

Alan

Eaglemax, I don't understand why you are standing on the soapbox and making such a big issue of this. The thread started with you pointing out that roads are roads wherever you are.

You seem to agree that the 10% guideline is less important the lighter the van is in relation to the tow vehicle. Yobarr effectively said the same when he agreed with my post saying just that.

Comparison with UK rules

On the other hand we have vehicle designers who make no such distinction (as per my posted images from the Ranger owners' manual). This is probably just to keep things simple.

Then we have caravan designers who don't want towball weight to scare off potential buyers so they keep them lighter than ideal. There is no point that a van suddenly changes from safe to unsafe due to towball weight. It is just degrees of safety. I doubt even you would disagree that a very light van towed behind a much heavier vehicle will be more roadworthy with 10% ball mass than with 5%.

I think you are being unneccessarily pendantic and preaching on semantics. It's a guideline. Time to chill out and move on.

 

-- Edited by Are We Lost on Thursday 24th of August 2023 01:19:47 PM

ARE WE LOST

Perhaps mate oyu hadnt read the initial reply (his 1st) on this thread when he insulted me. Such soap box was very present by him and so bad admin erased a lot of it. It resulted in my then reply of "my right to say it". But you didnt object to such soapbox then, you allowed it,

 

But when any member states their opinion the man will indeed lecture and you are ok with that? I'm pointing out where Yobarr stated a flaw in him quoting Collyn Rivers a man as Yobarr correctly claimed "is world renown" for his knowledge etc. And he was wrong. Hence the correction. If you dont like it then why respond? but you are free to do so. Perhaps you are immune to the abuse?

-- Edited by Eaglemax on Thursday 24th of August 2023 01:27:35 PM

-- Edited by Eaglemax on Thursday 24th of August 2023 02:19:52 PM

Thanks Yobarr. I was editing my post while you were writing your response so they don't quite match up. I have pasted the main part that I expanded.

Then we have caravan designers who don't want towball weight to scare off potential buyers so they keep them lighter than ideal. There is no point that a van suddenly changes from safe to unsafe due to towball weight. It is just degrees of safety. I doubt even you (Eaglemax) would disagree that a very light van towed behind a much heavier vehicle will be more roadworthy with 10% ball mass than with 5%.

And referring to Eaglemax's second post where he said .... "The point of the post is in my last sentence and in the topic heading. If you cant see that ........". That last sentence was (paragraph actually).

"If anyone can tell me of any major differences from roads in the UK to roads in Australia that more prevent sway in the UK I'm all ears. Isnt a road a road?"

I think that has been answered.

So like you said, I think it's time to walk away from that soapbox and leave the preaching to others to listen to. But if something evolves, then maybe ......

 

-- Edited by Are We Lost on Thursday 24th of August 2023 02:41:42 PM

Gundog wrote:

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I support Eagleamax on this one, there is far too much posted about TBW. TBW is the least of my concern, in fact I never preweigh the TBW, but I do take into account what is stamped on the compliance plate of the towbar.

For my vehicle that is 3000kg/250kg, which is roughly 8.3% TBW, you may wonder how this could be, it pretty simple this is a genuine Ford towbar for the PK Ranger series, the 250kg ball weight is because the automatic transmission is limited to towing 2500kg and the manual is 3000kg to avoid any confusion that is the reason for the 250kg ball weight. However if I purchased an aftermarket Towbar say from HR it would be a 3000/300kg compliance.

And the owners manual for the PK series states 10% TBW or what the ID plate affixed to the towbar states, whichever is the lowest.

How do I work out my towball weight very simple actual ATM - GTM = TBW, its not rocket science, and that is with the WDH engaged which is a requirement when towing ove 1800kg.

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 Your 8.3% ATM/TBW is fine imo Gundog. Some manufacturers build a car with say a 3500kg towing capacity but with a 200kg towball maximum weight. Then you see towbar manufacturers advertise a towbar they sell with 350kg ball capacity for that same vehicle. But the towball maximum set at the factory is 200kg and that is the maximum the towball can legally remain unless the manufacturer changes it by whatever means eg upgrade kit etc.  It is a bit silly from our perspective but it has a lot to do with the tow cars DNA than anything else.

 

I gather you havent had any sway issues?

-- Edited by Eaglemax on Thursday 24th of August 2023 02:36:00 PM

I notice that no-one has cited any research to back their positions, therefore I deem the 10% tow ball weight to be more myth than fact.
I have seen research results done in England which establish that 5 to 8 percent tow ball weight is best for recovery after a sway event is triggered.
It established that increasing tow ball weight beyond that increases the recovery time after a sway event is induced.
I know that the 10 percenters will clamour that is for light vans and light vehicles.
Well for light vans and vehicles, the physics gurus all know that the same laws apply whether using model masses that are orders of magnitude apart. That is why they are laws. It is why models are used in the design phase of almost every large object, whether it be buildings, cars, oil tankers, civilian and military aircraft, rockets or missiles.
Vehicle manufacturers determine the max tow ball weight as the tow ball weight affects the vehicle dynamics, but that is all they specify as they have no control over what you attach to that tow ball.

 Few common-sense points.

 

There is a lot of legal this and legal that here and data from manufacturers and opinions from You Tube and Forum experts and on and on.

Now, what about the Insurance Assessors in the case of rollovers, accidents, deaths and injuries.

Well, yes the Police are involved and they make notes in their log-books and their opinions are recorded and used in courts (that's why they record those notes at the time).

Also, the assessed speeds and braking at the time and other factors contributing to the accident.

The tow vehicle and caravan (and remains) are weighed and all safety aspects assessed.

No opinions here, on this blog, yet on Insurance claims after accidents. That's when the fun begins.

In this case, I would follow Yobarr and his opinions very carefully.

The Insurance assessor will look at all matters of opinion on safety and compliance and weight restrictions and take into account the Police notes at the time.

If it goes to Court those notes and opinions of an Officer at the time of the accident, inspection and data subsequently later will be closely scrutinized by the Insurance company.

There will be various opinions... Did you cause the accident, did others cause the accident, was there a safety factor causing the accident and so on.

What I see is that opinions from Yobarr caution on the safety side of towing and if you are a victim of an accident (whether your fault or not) I would lean upon opinions of Yobarr than many others here.

If you insure your towing rig you will need to have a very comprehensive view of all matters relating to towing.

Yobarr is safety motivated.