Towing

[Mikek777]

Thought this was interesting and it conforms to rules applied by DVSA, FTA & RHA

https://blueskyrecreation.wordpress.com/2017/06/27/85-of-kerb-weight-law-guide-or-myth/

 

[Raywood]

It raises some interesting points and most of it is correct. The towing limit though is the limit at which the car can restart on a 12% hill so that is incorrect. What the towing characteristics are is not taken into account and there is no evidence the car is often any difference where a larger engine is fitted. Certainly with my car there are four engine variations available and the makers certainly claim no adjustment it to cover this.
Frankly you exceed the 85% figure as a starter at your peril although personally I would say with modern cars and suspension 90% is usually realistic and probably up to 95% for the more experienced. Every combination has different towing characteristics though so caution is probably the best bet.
The article also misses the point that towing at the cars limit will probably very slow, and power/weight ratios must be taken into account or you might be a mobile traffic jam.

 

[timhowarduk]

A good article.
My only comment (and I admit I'm nit picking) is that I take slight exception to the suggestion that a stabiliser hitch can improve the basic physics to a degree that a heavier load can be safely towed. I feel stabilisers are best viewed as devices to make a safe combination even safer, as opposed to improving the handling of an unwieldy combination to make it safe.

 

[Hutch]

When I first trarted towing our first caravan it was abiout an 90% ratio, I changed the caravan and decided I needed a more powerfull car, which ended up being lighter so we were at about 100% . Sensible towing it was great but after strong side winds, decided to get a heavier car, . If I toured only a few time a year it would not be a problem . But we travel all year round in all weather.
Happy towing to all.
Hutch.

 

[Raywood]

I agree that a stabiliser of any type should be an additional safety device and not something to justify towing a higher weight.
The problem with the weight ratio is that the safe weight you can tow will vary from car to car, and with the caravan on the back as the towing characteristics of different makes and models vary. Erring on the safe side is the best advice as you only find out if you got it wrong when it is too late.

 

[camel]

Can't wait for the Prof to put his six pennies worth in , in fact the Prof could of penned it, ha, ha, only a joke Mod's,

 

[ProfJohnL]

Can't wait for the Prof to put his six pennies worth in , in fact the Prof could of penned it, ha, ha, only a joke Mod's,

I'll actually put a whole shillings worth in for you Camel. No I didn't write it but its what I have basically been saying for years! hmy: .

However there is is one error, The licence restriction mentioned did not use the Kerbweight ( which has no legal definition) but actually uses the UnLaden Weight, (ULW) which is not the same as Kerbweight

 

[camel]

Prof,
It was not a criticism but reflecting on what you have been saying in many posts about the 85% towing limit which I think was plucked out the air years ago,

 

[Parksy]

Prof,
It was not a criticism but reflecting on what you have been saying in many posts about the 85% towing limit which I think was plucked out the air years ago,

I've beaten the Prof to it :cheer: by pointing out that the 85% figure is not a limit, it's an advisory figure but it wasn't simply plucked out of the air as you suggest.
The figure was originally arrived at because some years ago the CC (now C&MC) worked with Bath university to recommend a safe towing ratio between car and caravan.
Car design has changed considerably since the figure was first recommended, but the consensus of informed opinion suggests that as a starting point for those new to towing, the 85% recommendation, along with correct caravan maintenance and loading procedures and good driving techniques, is still considered to be a safe towing ratio.

 

[JTQ]

Prof,

Car design has changed considerably since the figure was first recommended, but the consensus of informed opinion suggests that as a starting point for those new to towing, the 85% recommendation, along with correct caravan maintenance and loading procedures and good driving techniques, is still considered to be a safe towing ratio.

That consensus then surely with zero references to anything but the car's mass can only be based on the most dreadful towcar the beginner might have, as long as it is heavy enough, then it is considered safe for towing.

Not really reputable university thinking I suggest as anyone with a bit of knowledge in the subject knows other factors also have powerful influences.
It would be hugely more valuable if the advisers listed for all the various popular car choices a specific guidance MPTM figure..
I agree some guidance is needed but a mass ratio only one is technically flawed and unduly inhibiting.

Edit: an ideal tool TCOY, a caravanning magazine and caravanning based clubs could so simply do by pulling data off the installed ATC units used in the towing tests.

 

[otherclive]

Car design has changed considerably since the figure was first recommended, but the consensus of informed opinion suggests that as a starting point for those new to towing, the 85% recommendation, along with correct caravan maintenance and loading procedures and good driving techniques, is still considered to be a safe towing ratio.

That consensus then surely with zero references to anything but the car's mass can only be based on the most dreadful towcar the beginner might have, as long as it is heavy enough, then it is considered safe for towing.

Not really reputable university thinking I suggest as anyone with a bit of knowledge in the subject knows other factors also have powerful influences.
It would be hugely more valuable if the advisers listed for all the various popular car choices a specific guidance MPTM figure..
I agree some guidance is needed but a mass ratio only one is technically flawed and unduly inhibiting.

Edit: an ideal tool TCOY, a caravanning magazine and caravanning based clubs could so simply do by pulling data off the installed ATC units used in the towing tests.

Bath University did a lot of work with Bailey and I think that the demo model was really to show people the effects of end loads on stability. It was more a visual aid.
However, I support the 85% guide for those new to towing as it erred on the side of safety, but isnt a guarantee of stability so the van should still be loaded as per advice. so many things will affect stability and how an outfit reacts when on the road that its almost impossible to provide meaningful data across the spectrum of cars, vans and drivers. If people are sensible and take as much advice as is available from Forums, Clubs and Owners, do a Club course etc then they should be able to start off at a safe level. With experience they will then be able to make decisions on changes.
I note on Alkos website for ATC that they still advise sensible loading and load distribution. As even with ATC and the car's Trailer Assist, or ESP one doesn't know if they can be guaranteed working whilst driving. The car might throw a dashboard warning but does ATC?

 

[Mikek777]

Unladen weight (ulw) is the birth weight, no fuel, no oil, no driver, this is often referred to as the vehicle's dry weight or as it would be at the end of the factory production line.

Kerb-side weight The unladen weight of the vehicle excluding driver or any other person, but including the weight of water, fuel (accumulators), loose tools and loose equipment with which it is normally equipped.

Gross laden weight - The sum of the weights transmitted to the road surface by all the wheels of the vehicle, including body and parts, water, fuel (accumulators) loose tools and equipment, driver and load at any given time.

Gross vehicle weight (GVW) The legal maximum weight of a vehicle, including body and parts, water, fuel (accumulators), loose tools and equipment, driver and load. Other expressions used to indicate these legal maximum weights are permissible maximum weight (PMW), maximum gross weight (MGW) and maximum authorised mass (MAM)

Gross plated weight (GPW). The maximum permitted gross weight of a vehicle (rigid, articulated including semi-trailer or road train) and of individual axles, not to be exceeded in Great Britain, as shown on the DfT plate, or the manufacturer's plate if the vehicle has not been plated by the DfT

Gross train weight (GTW) For a vehicle which may draw a trailer or for an articulated vehicle, the legal maximum permitted weight for the vehicle together with and trailer(s) drawn - i.e the maximum the laden vehicle and trailer can weigh when complete vehicle is placed on a weighbridge.

Then may favourite Gross combination weight (GCW) The gross train weight of an articulated vehicle is sometimes referred to as gross combination weight. This is a different term but in practice is the same as GTW.

 

[GD485]

As the Prof often points out the 85% is a good basic guide figure. However a match at 50% could be far more dangerous than a careful configured 100% match.

This is particularly so when the addition of all the electronic toys in both car and caravan can help when things go bad.
Most new caravans now have shock absorbers fitted which is another simple but effective aid to a stable set-up.
Basic checks and vehicle servicing can be just as effective at producing stability rather than paying attention to a few percentage points either way in towing ratio.

As long as the basics of loading are adhered to and the owners is aware of the behaviour changes that towing a 1.5 ton box has on the performance of a tow car then half the battle is won.

Ignorance is more dangerous than some towing ratio dreamed up a few decades ago that may well be out of date for todays combinations.
I consider the majority of Caravaners that read or contribute to this forum have more than passing interest in the safety of their combination and therefore the more dangerous set-up's belong to those that can't be bothered to service, check tyres, tow car suitability and their driving licence before dragging the caravan out of storage and tearing off to the west country.

 

[JTQ]

Quoting "[u]I note on Alkos website for ATC that they still advise sensible loading and load distribution. As even with ATC and the car's Trailer Assist, or ESP one doesn't know if they can be guaranteed working whilst driving. The car might throw a dashboard warning but does ATC?/u]"

Good to hear they do as they don't sell their ATC, despite its name, as means of living with instability. It is the last resort to stop instability doing its worst. If one was stupid enough to live with a level of instability requiring its near constant intervention the brake drums would soon be burnt away and your fuel consumption will be dire.
There is no dashboard warning of the ATC intervention, but my experience is its action is very evident. In a way comfortingly so as you know it's there doing what it should, though not quite sophisticated enough for it to realise that the sway was a bit too tight a bend or a lumpy CL field.
I am in the camp of liking its simplicity, that way it is something I can afford so have it, plus without over complexity raming up unreliability issues.

 

[camel]

I'm well aware of the 85% towing ratio what the great and the good decided to do when they decided at their annual jolly to proclaim, ' 'Eureka' it's 85%', my own opinion for what it's worth is that when some one is new to caravanning even people with grandfathers rights to tow a caravan, should have to attend a course on towing and and what the various weight limits stand for on a caravan plate,

 

[GD485]

In some ways the 85% figure is much use as "42 is the meaning of life, the universe and everything" ( Adams. The Hitch hikers guide).

 

[otherclive]

In some ways the 85% figure is much use as "42 is the meaning of life, the universe and everything" ( Adams. The Hitch hikers guide).

I have read your previous post and this one. I would really like to hear your detailed explanation to a "newbie" as to how they should go about selecting and using an outfit that doesn't put themselves, their family or others at unnecessary risk. In none of the previous posts has anyone said the adherence to the 85% guide is a guarantee of safety, but you seem very dismissive, though in an earlier post you seem supportive. So what would be your approach for a "newbie"?

 

[GD485]

I might have been less than helpful to a new caravaner but I was taking part in the conversation and not necessarily answering the OP much like the others before me. I am sorry if i have been unduly dismissive that was not my intention.
I think the general information given by all the other contributors has outlined the fact the too much reliance on some figure is not going to be a sure route to a stable and safe outfit.

 

[ProfJohnL]

This thread is unintentionally doing what I have complained about...
Obsessing about the importance of following a notional weight ratio, and failing to bring some of the other potentially more important aspects of setting up an outfit to the party.

Nose load,
Vehicle condition
Driving habits

Weights are not unimportant, after all there are some legal limits that must be observed, and whilst the 85% is only guidance, it is not without some merit. It at least alludes to the principal of keeping the mass of any trailer as minimal as possible.

However harking back to an earlier post

Prof,
It was not a criticism but reflecting on what you have been saying in many posts about the 85% towing limit which I think was plucked out the air years ago,

I've beaten the Prof to it :cheer: by pointing out that the 85% figure is not a limit, it's an advisory figure but it wasn't simply plucked out of the air as you suggest.
The figure was originally arrived at because some years ago the CC (now C&MC) worked with Bath university to recommend a safe towing ratio between car and caravan.
Car design has changed considerably since the figure was first recommended, but the consensus of informed opinion suggests that as a starting point for those new to towing, the 85% recommendation, along with correct caravan maintenance and loading procedures and good driving techniques, is still considered to be a safe towing ratio.

I'm quite surprised Parksy at your comment. I'm not sure where you have got your information from.

Despite having made extensive enquiries of the clubs, and a number of industry insiders over the years, None of my contacts could throw any formal light on the process used to derive the guidance except it was a committee decision. I could not establish the names or anything about who might have been on the committee.

It has also been equally frustrating to find that no one can point to the method or evidence used to come to any conclusions, so it certainly gives the impression the 85% advice was not based on scientific evidence.

Although I am critical of the curtain of silence the industry has drawn around the source of the advice, I am pretty certain the advice was produced in good faith, and based on the information available at at the time. which compared to today was not very extensive.

Parksy unless you have come into possession of some new information, I have never found any evidence that any University was involved in producing the industry guidance. The University of Bath (to give it it's correct name) was only founded in 1966, so I suspect it wasn't even established when the guidance was issued.

The University did collaborate with Bailey caravans to look at the towing characteristics of a Bailey caravan. It was part of that research which produced the oft refereed to model that demonstrates the effect of yaw inertia. The result of that study was limited to describing the characteristics of one particular car and caravan, and could not be used to as evidence of a general case for all possible combinations.

At no time has the industry formally linked the 85% guidance with any guarantee of safety, or legality, that has evolved with the numerous times the guidance has been misquoted.

I believe informed opinion is actually divided about the efficacy of the advice, but there is a consensus that until a better more reliable method has been formulated, flawed as it is the 85% guidance is a lot better than nothing, and is a starting point.

 

[GD485]

I agree whole heartedly with your comments regarding the 85% guide is a starting point. It's not a hard and fixed point of reference that must not be deviated from.
Therefore it is difficult to guide anyone to a fail safe position regarding towing ratio. There is just too many variables involved to be able to simplify the matter to a single figure.

 

[Mikek777]

I believe the 85% figure may have started out a little bit higher, but to be prudent it may have been reduced to 85% to ensure advice given was indeed safe advice, no one would want to be remembered for issuing a figure and accidents and injury were the result of following said advice.
The other issue of caravans is the single axel which is in the middle of the trailer, this makes it difficult to load if you have no understanding of spreading the load and not exceeding individual axel weights (rear of car included) you don't see transport companies searching their yards looking for a tractor unit that will match the loaded trailer based on 85%, because the configuration of the trailer is different. Its a harder job to load a caravan safely and get the correct balance than it is a truck I have to say.

 

[ProfJohnL]

I believe the 85% figure may have started out a little bit higher, but to be prudent it may have been reduced to 85% to ensure advice given was indeed safe advice, no one would want to be remembered for issuing a figure and accidents and injury were the result of following said advice.
The other issue of caravans is the single axel which is in the middle of the trailer, this makes it difficult to load if you have no understanding of spreading the load and not exceeding individual axel weights (rear of car included) you don't see transport companies searching their yards looking for a tractor unit that will match the loaded trailer based on 85%, because the configuration of the trailer is different. Its a harder job to load a caravan safely and get the correct balance than it is a truck I have to say.

You have touched on an interesting comparative point.
I must point out that legally the drivers of caravan and full articulated lorry outfits have the same responsibility to ensure their vehicle is loaded correctly and conforms to construction and use regulations, As well as driving lawfully,

The difference is to be an HGV driver today you have to pass a more advanced test that includes elements about loading and securing loads. There is no such formal training for basic car and caravans with a combined MAM of less than 3500kg

Its also worth noting that Articulate lorries have a very different mechanical layout, and the effects of load mass are are less counter to stability in an HGV becasue of the position of the trailer wheels right at the rear of the trailer and the hitch being the fifth wheel which is mounted within the tractor units wheel base.

I do note there are quite a number of rigid HGV's that now have a drawbar trailer, and these will behave more like a caravan

 

[camel]

Exactly my point in my earlier post, a person can just come along and buy a caravan and drive away if they are qualified to do so, and then come on to caravan forum sites like this and start to ask about N/S and the 85%, I personally think that there should be some compulsory awareness training for towing caravans,

 

[Craigyoung]

I agree , there are some right idiots on our roads , I see this everyday as I am a bus driver (a happy one) ! many times when we're on the motorway and I am doing around the 60'ish mark , there are always people flying past me doing at least over 70 and I cringe at the thought of them losing control with that caravan in tow

 

[Parksy]

....I'm quite surprised Parksy at your comment. I'm not sure where you have got your information from.

Despite having made extensive enquiries of the clubs, and a number of industry insiders over the years, None of my contacts could throw any formal light on the process used to derive the guidance except it was a committee decision. I could not establish the names or anything about who might have been on the committee.

It has also been equally frustrating to find that no one can point to the method or evidence used to come to any conclusions, so it certainly gives the impression the 85% advice was not based on scientific evidence.

Although I am critical of the curtain of silence the industry has drawn around the source of the advice, I am pretty certain the advice was produced in good faith, and based on the information available at at the time. which compared to today was not very extensive.

Parksy unless you have come into possession of some new information, I have never found any evidence that any University was involved in producing the industry guidance. The University of Bath (to give it it's correct name) was only founded in 1966, so I suspect it wasn't even established when the guidance was issued.

The University did collaborate with Bailey caravans to look at the towing characteristics of a Bailey caravan. It was part of that research which produced the oft refereed to model that demonstrates the effect of yaw inertia. The result of that study was limited to describing the characteristics of one particular car and caravan, and could not be used to as evidence of a general case for all possible combinations.

At no time has the industry formally linked the 85% guidance with any guarantee of safety, or legality, that has evolved with the numerous times the guidance has been misquoted.

I believe informed opinion is actually divided about the efficacy of the advice, but there is a consensus that until a better more reliable method has been formulated, flawed as it is the 85% guidance is a lot better than nothing, and is a starting point.

I have to confess that my comment is not based on any new information but was a paraphrase of several old forum posts and website articles that suggested that the 85% figure was first introduced by the CC (C&MC) after work was done by Bath University.
This may or may not be correct, it's an opinion arrived at through reading what has been written by others, not an incontrovertible fact.
There's no doubt at all that both the Camping and Caravanning Club and the Caravan and Motorhome Club both endorse the 85% guideline, so it's not terribly relevant who first introduced it because the advice hasn't changed to my knowledge.
I have no idea when the 85% figure was first recommended, and I suspect that neither do you Prof, but again, the point is that the 85% towing ratio figure continues to be the advice offered to those new to towing.
The consensus of what I would regard as informed opinion does indeed suggest that when other safety considerations that I mentioned previously are taken into account the 85% towing ratio recommendation is a sensible and safe figure for new caravanners to aim for if they have little or no previous towing experience with the inference being that towing ratio's which significantly exceed the 85% figure are not recommended.
I don't remember stating that the caravan industry had formally linked the 85% towing ratio recommendation with any guarantee of safety or legality, so it's difficult to understand why you appear to suggest that I have.