We are thinking of up grading the car to a New Ford Grand C-Max 2.0 TDCI Auto will it pull this Lunar Ultima 544 Caravan

[Lutz]

It is now 14 years since UK law has placed restrictions on the weight of caravan that can be towed by B licence holders unless they take a further trailer test.
Presumably this change was in recognition that drivers new to towing need to gain experience before towing heavier trailers.

If one were to go by the licence restrictions which, as you say, are "in recognition that drivers new to towing need to gain experience before towing heavier trailers", then this would be a case for adopting a 100% max. weight ratio recommendation, as that is basically what the licence restriction amounts to.
As has been mentioned in previous threads on the same subject, the prevailing towing conditions and the car's and caravan's technical equipment have a marked effect on stability. An outfit which is perfectly docile at 100% could be an absolute pig to handle in anything but a mild breeze. To my mind there is nothing irresponsible in recommending a 100% weight ratio limit subject to the car being fitted with ESP+ or the caravan with an electronic stabiliser and the caravan with shock absorbers. One could leave the 85% recommendation for those outfits not benefitting from such fitment.

 

[mat1]

http://www.outandaboutlive.co.uk/Caravans/Features/Editorial/Why-90-should-be-the-new-85-caravan-weight-call/_ch2_ft317

Mat

 

[Lutz]

The above article is interesting and worth further study, but it, too, doesn't provide any factual evidence that 90% is any more appropriate than 85%. What is needed is a direct comparison that quantifiably demonstrates by how much stability is affected by a corresponding change in weight ratio. This is sadly lacking. Maybe there is no appreciable difference between 85% and 90%. We assume that there is, but who knows for sure?

 

[mat1]

The above article is interesting and worth further study, but it, too, doesn't provide any factual evidence that 90% is any more appropriate than 85%. What is needed is a direct comparison that quantifiably demonstrates by how much stability is affected by a corresponding change in weight ratio

Is there a chance the magazine would canvass those named in the article ??
Maybe an up to date "re study" with the findings published by PC.
Does anyone have contacts with universities that would run this as part of a theory test experiment.

Mat

 

[ProfJohnL]

Hello Parksy,

to answer your question;

"Do you consider the 85% weight ratio recommendation to those inexperienced in towing to be bad or confusing advice?"

The principal behind the advice advice is not intrinsically bad, provided it is part of a broader trange of advice or information concerning safe loading and driving etc, and that it clearly indicates it is an indicator rather than a limit.

I do think the advice is confusing, because it is all too often referred to as a 'rule' I note from the paper that Mat points to that the the quote from the C&CC near the bottom actually uses the word rule!

I do recall seeing the article Mat points to previously, in fact not long after I first gave my consideration to the nature of the use of 85%. It actually parallels my own thinking very strongly.

I had forgotten the quote from the CC concerning their claimed methodology:

"The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research to help deliver a safe and comfortable towing experience for drivers of all abilities."

Fine words but where is the evidence and the quality control.?

Ultimately I think the quote from Dr Darling of Bath University sums up variability :-

"Simply put, a badly loaded 85% match is dangerous whereby a safely loaded 90% match is not.”

The issue is to complex to reduce it to a single one size fits all number.

 

[Parksy]

Hello John
The 85% advice is part of an wider advice package and is aimed primarily at inexperienced towcar drivers or those new to caravanning.
If you read the advice you will see that there is no mention of 85% as a limit.
The first line in the 'Matching Your Outfit' guide reads: 'As a newcomer to caravanning..................'
The advice goes on to state that for more experienced drivers such as those who have driven articulated vehicles or towed high sided trailers a ratio of up to 100% is acceptable under normal road conditions.


The advice given by the CC does not refer to these recommendations as being a rule. This is a colloquialism adopted by the general public and is not terribly important if it prevents a newbie from purchasing a caravan which is unsuitable for his towing vehicle and from making a potentially expensive mistake or from endangering himself or others.

You have conceded that the advice is not bad advice, the available advice given by organisations consists of much more than the 85% recommendation which is just a starting point as we have already discussed.
Caravan forums, in spite of their colloquial terminology, also contain a wide range of supplementary advice for inexperienced caravanners and potential purchasers.

Organisations including both clubs basically say the same thing, for me their word is good enough. The CC stated:

"The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research to help deliver a safe and comfortable towing experience for drivers of all abilities."

I find it highly unlikely that the CC would refer to 'outfit testing and academic research' that had not been carried out John.
Why would the casual enquirer or the newcomer to caravanning for whom the advice is primarily intended require the detailed evidence which gave rise to this statement?

I would accept the need for evidence to be provided if I considered the advice to be bad or the 85% recommendation to be wrong but I don't, and neither does any reputable caravanning organisation or publication including, presumably, the Practical Caravan Magazine.
I would also accept your approach more readily if I considered either of the clubs to be disreputable or untrustworthy but I don't and neither do the vast overwhelming majority of caravanners, organisations or publications.

"Simply put, a badly loaded 85% match is dangerous whereby a safely loaded 90% match is not.”

By the same token a badly loaded 90% match is dangerous whereby a safely loaded 85% match is not and the same thing could be said of almost any figure, which invalidates that supposition as far as this discussion is concerned because all badly loaded caravans are potentially dangerous.

I wouldn't accept that this issue has been reduced to a one size fits all number John, the 85% figure is used as a starting point recommended for new caravanners along with a substantial amount of further information about all aspects of caravanning, and taken in context I have no problem at all with that.

 

[Gafferbill]

It is now 14 years since UK law has placed restrictions on the weight of caravan that can be towed by B licence holders unless they take a further trailer test.
Presumably this change was in recognition that drivers new to towing need to gain experience before towing heavier trailers.

If one were to go by the licence restrictions which, as you say, are "in recognition that drivers new to towing need to gain experience before towing heavier trailers", then this would be a case for adopting a 100% max. weight ratio recommendation, as that is basically what the licence restriction amounts to.

…..I hesitate to post again during this eloquent discussion between the Prof and Parksy especially as it will confuse new towers even more.
The facts are that a B licence towing restrictions (since January 1st 1997) refer back to the towing vehicles Unladen Weight and not to its Kerbweight as does the 85% recommendation under discussion.
Simple direct comparisons cannot be made.
Accurate comparisons would bring the measurement of two ratios closer together.

 

[Lutz]

"Simply put, a badly loaded 85% match is dangerous whereby a safely loaded 90% match is not.”
By the same token a badly loaded 90% match is dangerous whereby a safely loaded 85% match is not and the same thing could be said of almost any figure, which invalidates that supposition as far as this discussion is concerned because all badly loaded caravans are potentially dangerous.

The very fact that both the above statements are true already legitimises questioning the usefulness of any percentage recommendation.

The facts are that a B licence towing restrictions (since January 1st 1997) refer back to the towing vehicles Unladen Weight and not to its Kerbweight as does the 85% recommendation under discussion.

Simple direct comparisons cannot be made.
Accurate comparisons would bring the measurement of two ratios closer together.

And where, pray, does the owner find details of the unladen weight of his/her car? The only source is the V5c certificate which quotes "Mass in Service" and not unladen weight. Although there is technically a difference between the two, the DfT have confirmed that until the terminology in the law is brought up to date, "Mass in Service" is to be interpreted as being the unladen weight.
There is no legal definition of kerbweight. What it includes or does not include is covered by convention only. Most car manufacturers nowadays choose to quote kerbweight according to the respective EU Directive covering "Mass in Running Order", which is the same as "Mass in Service".
Hence, for all practical purposes, kerbweight, unladen weight, Mass in Service and Mass in Running Order are one and the same thing unless the car manufacturer quotes a kerbweight not in line with the EU Directive.
Besides, kerbweights published in brochures, websites, or other literature, are usually so far off the actual figure that the margin or error is larger than any differences in definition from unladen weight, etc.

 

[Gafferbill]

OK

 

[Lutz]

I am fully aware of the information published in the DirectGov website, but unladen weight, according to the definition supplied, is not documented anywhere. Because this is the case, the DfT have selected to reinterpret the term 'unladen weight' as being the same as Mass in Service, although this is not in line with the definition supplied in the DirectGov website. Otherwise, the powers-that-be would have no way of checking whether anyone was legal or not.

 

[ProfJohnL]

Hello Parksy,

I don't deny that 85% is part of a wider range of issues alluded to by the clubs, but It is my distinct impression the greatest emphasis is still given to weight ratios. It is certainly the case that questions about weights in relation to towing stability are the most frequent single question for towers new and old.

It is also very telling that so many people who still refer to 85% as a rule or other some sort of official value.

I'm sorry to be pedantic, but I actually wrote

"The PRINCIPLE BEHIND the advice advice is not intrinsically bad" not as you wrote "You have conceded that the advice is not bad advice" The difference is subtle but important.

Let me clarify another nuance of my position. I am challenging the committees decision to recommend 85%, on the basis that they have provided no evidence to support that recommendation or the assumptions they used in their deliberations.

Not withstanding the probability that you cannot reduce all the towing characteristics into some descriptive single number, I do not automatically assume that the optimum recommendation should be greater than 85%, though there is sufficient pressure of opinion to suggest it should at least be investigated.

The practical upshot of the 85% advice is the way it has been used over the years and it has become dogma, repeated by so many people that its used now without any thought of how it was derived. There must be many people who will assume like you, that the clubs must have the technical experience to correctly assess the evidence when considering the advice they came up with.

Just consider similar examples that over time have been proven to be wrong:-

• Earth centred solar system (or even universe)
• Flat earth
• Speed at which the human body would fall apart (before trains)

In all these cases what may have appeared a trusted body of people (in the context of their era) made pronouncements about these "certainties", only over time and with better educated masses we actually now ask 'why do you hold that view'. Ultimately with better experimental open processes those 'certainties' are now thoroughly dis-proven.

What it shows is the pronouncements given out by what were considered trusted bodies at the time was in fact flawed. It may be the data was inadequate, or in some cases the data or decisions were deliberately skewed for a hidden agenda, but the masses were told this is right and through dogmatic repetition they repeated the inaccuracies. - Sounds familiar?

Call me a heretic but I'm sorry I believe there is sufficient logical grounds to suspect that 85% is not necessarily best advice, a point that is supported by the contributors to the document that Mat refers. I do acknowledge that the caravan manufactures in the document would be served well if the advice were revised upwards, and I do not necessarily look for the same outcome but maintaining safety must be paramount.

If the clubs technical committees want their advice to have qudos, they should be more than happy to have their work and their decisions reviewed in the open. Without access to that level of openess it could be wrong to assume this important safety issue can be just accpeted at face value.

I will happily accept 85% as long as the evidence can be provided that shows it it the best figure for the job. Statements that simply say a hidden group of people say it's right is not enough.

As a gesture of goodwill, I do accept that 85% advice is better than none at all, but I insist that this comment must considered in the context of this posting.

 

[Dustydog]

An imense amount of knowledge and sense has been put into all the posts on this thread.

Maybe one of of our "wise men" in plain simple English could give a few simple basic pointers to the newbies who frequent this site and help them to understand what they need to do to be "safe".
Thankyou

 

[Lutz]

In addition to obviously complying with mandatory regulative restrictions and the limits imposed by the car and caravan manufacturers' specifications, one should aim to:
1. Keep the caravan as light as possible and make as much use of the car's available payload as possible (regardless of any weight ratio recommendation).
2. Ensure that the noseweight is as close as possible to the respective limits for car and caravan, of course without exceeding them.
3. Distribute the payload in the caravan as low and as close to the axle as possible, not forgetting to secure any heavy items against shifting around while travelling. Try to ensure that the load distribution is also more or less equal between the left and right hand side.
4. Have shock absorbers installed on the caravan, if not already fitted.
5. If budget allows, use a towcar with trailer stability control, sometimes also referred to as TSA or TSP. An electronic stabiliser on the caravan provides an even greater margin of safety although it is appreciated that this is beyond the budget constraints of many. A frictional or viscous stabiliser is a good compromise which also lends itself to serve as a complimentary feature in addition to an electronic system for optimal protection.
6. Check that the tyre pressures of car and caravan are in accordance with those specified for the respective loading conditions.
7. Drive with even more due care and foresight than when driving solo and slow down at the first signs of any 'twitchiness'.
8. This may be obvious, but I mention it nevertheless - ensure that both the car's and caravan's brakes are in proper working order and, of course, the tyres are appropriate for the loads carried and in good condition.
Observing all of the above is, to my mind, more important than simply keeping within any weight ratio which, more often than not, doesn't reflect the actual conditions anyway.

 

[Dustydog]

In addition to obviously complying with mandatory regulative restrictions and the limits imposed by the car and caravan manufacturers' specifications, one should aim to:
1. Keep the caravan as light as possible and make as much use of the car's available payload as possible (regardless of any weight ratio recommendation).
2. Ensure that the noseweight is as close as possible to the respective limits for car and caravan, of course without exceeding them.
3. Distribute the payload in the caravan as low and as close to the axle as possible, not forgetting to secure any heavy items against shifting around while travelling. Try to ensure that the load distribution is also more or less equal between the left and right hand side.
4. Have shock absorbers installed on the caravan, if not already fitted.
5. If budget allows, use a towcar with trailer stability control, sometimes also referred to as TSA or TSP. An electronic stabiliser on the caravan provides an even greater margin of safety although it is appreciated that this is beyond the budget constraints of many. A frictional or viscous stabiliser is a good compromise which also lends itself to serve as a complimentary feature in addition to an electronic system for optimal protection.
6. Check that the tyre pressures of car and caravan are in accordance with those specified for the respective loading conditions.
7. Drive with even more due care and foresight than when driving solo and slow down at the first signs of any 'twitchiness'.
8. This may be obvious, but I mention it nevertheless - ensure that both the car's and caravan's brakes are in proper working order and, of course, the tyres are appropriate for the loads carried and in good condition.
Observing all of the above is, to my mind, more important than simply keeping within any weight ratio which, more often than not, doesn't reflect the actual conditions anyway.

An excellent precis. Thanks Lutz.
However any decent dealer will still use weight ratio guides to tell a customer if their vehicle and proposed caravan purchase are compatible. And as you all say what is compatible??

 

[Gafferbill]

This is a good guide to caravaning issued by the organisations stated on its cover who surely as Parksy indicated in his posts, have more weight behind them (see what I did there!) ......than any of us on here.

http://www.nationalcaravan.co.uk/images/resources/Caravan_Towing_Guide_080805.pdf

 

[Parksy]

Hello Parksy,

I don't deny that 85% is part of a wider range of issues alluded to by the clubs, but It is my distinct impression the greatest emphasis is still given to weight ratios. It is certainly the case that questions about weights in relation to towing stability are the most frequent single question for towers new and old.
Sorry John but your impression could be said to be subjective.
I concur that caravan forums frequently feature questions about weights in relation to towing stability but my point is that the 85% recommendation was intended to provide some guidance (along with other advice) primarily to potential buyers of tourers which would prevent these buyers from purchasing a tourer which would be too heavy for their towing vehicle at the outset.
The 85% recommendation is not i.m.o. meant to be taken as a general guideline for every situation and the context of the questions about weight in relation to towing stability should be addressed individually and contextually.

It is also very telling that so many people who still refer to 85% as a rule or other some sort of official value.

I'd agree that this is wrong, so is poisoning puppies or bombing innocent civilians in Afghanistan but these things are rather difficult for us on PCv forum to prevent.

I'm sorry to be pedantic, but I actually wrote

"The PRINCIPLE BEHIND the advice advice is not intrinsically bad" not as you wrote "You have conceded that the advice is not bad advice" The difference is subtle but important.
Point taken
Let me clarify another nuance of my position. I am challenging the committees decision to recommend 85%, on the basis that they have provided no evidence to support that recommendation or the assumptions they used in their deliberations.
Are they legally obliged to do this?
They may have reasons of which neither you or I are aware for them not to provide this evidence, or it may be available but you haven't found it.

Not withstanding the probability that you cannot reduce all the towing characteristics into some descriptive single number, I do not automatically assume that the optimum recommendation should be greater than 85%, though there is sufficient pressure of opinion to suggest it should at least be investigated.
This pressure of opinion wouldn't be initiated by caravan manufacturers who continue to design caravans which are increasing in weight would it by any chance?
The practical upshot of the 85% advice is the way it has been used over the years and it has become dogma, repeated by so many people that its used now without any thought of how it was derived. There must be many people who will assume like you, that the clubs must have the technical experience to correctly assess the evidence when considering the advice they came up with.
I accept your point that the advice has been used in a dogmatic manner, it should be used in the appropriate context but when the advice is used in the correct context it is good advice i.m.o.
I have no reason to suppose that the CC or C&CC do not have access to the technical expertise which has assessed the evidence that they have stated publicly that they possess to arrive at advice that is considered correct by the overwhelming majority of caravan organisations and publications.
Are you in a position to prove that the Caravan Club have made an untruthful statement when they wrote:
'The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research to help deliver a safe and comfortable towing experience for drivers of all abilities'
Just consider similar examples that over time have been proven to be wrong:-

• Earth centred solar system (or even universe)
• Flat earth
• Speed at which the human body would fall apart (before trains)

In all these cases what may have appeared a trusted body of people (in the context of their era) made pronouncements about these "certainties", only over time and with better educated masses we actually now ask 'why do you hold that view'. Ultimately with better experimental open processes those 'certainties' are now thoroughly dis-proven.
I see your point John and accept that society may no longer accept some matters at face value.
The CC have already told us that their view is based upon a 'combination of member feedback, outfit testing and academic research.'
I'm happy to accept this statement because the reputation gained over the years by the CC suggests to me that they wouldn't lie or attempt to mislead their members, especially in the face of the aforementioned 'pressure of opinion' to alter their recommendation.

What it shows is the pronouncements given out by what were considered trusted bodies at the time was in fact flawed. It may be the data was inadequate, or in some cases the data or decisions were deliberately skewed for a hidden agenda, but the masses were told this is right and through dogmatic repetition they repeated the inaccuracies. - Sounds familiar?
I find it difficult to believe that the CC would deliberately skew decisions or data in the way that you seem to suggest John, what would they hope to gain by holding a 'hidden agenda' which meant that potential caravan buyers and those inexperienced in towing caravans would be offered the wrong advice?
Call me a heretic but I'm sorry I believe there is sufficient logical grounds to suspect that 85% is not necessarily best advice, a point that is supported by the contributors to the document that Mat refers. I do acknowledge that the caravan manufactures in the document would be served well if the advice were revised upwards, and I do not necessarily look for the same outcome but maintaining safety must be paramount.
My contention is that the body of authoritative opinion which continues to support the advice is sufficient to convince me that the advice when used in the correct context is good advice.

If the clubs technical committees want their advice to have kudos, they should be more than happy to have their work and their decisions reviewed in the open. Without access to that level of openness it could be wrong to assume this important safety issue can be just accepted at face value.
I will happily accept 85% as long as the evidence can be provided that shows it it the best figure for the job. Statements that simply say a hidden group of people say it's right is not enough.
Do you have evidence to prove that these technical committees have been secretive? I don't consider the CC to be a hidden group of people and because their evidence is not immediately visible to the general public or that they chose not to discuss it with me personally I wouldn't assume that it doesn't exist.
It would be accepted by many people that HM the Queen is quite wealthy but we don't need to be able to count her money to accept this and we wouldn't be allowed to anyway.

As a gesture of goodwill, I do accept that 85% advice is better than none at all, but I insist that this comment must considered in the context of this posting.
Fair comment but I do hope that we don't have to go through all of this rigmarole every time a newbie asks what sort of caravan they should consider buying

Apologies for using this format with which to address your points John but time pressure prevented me from composing a reply in a separate comment box.

 

[Lutz]

Are you in a position to prove that the Caravan Club have made an untruthful statement when they wrote:
'The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research to help deliver a safe and comfortable towing experience for drivers of all abilities'
I will happily accept 85% as long as the evidence can be provided that shows it it the best figure for the job. Statements that simply say a hidden group of people say it's right is not enough.
Do you have evidence to prove that these technical committees have been secretive? I don't consider the CC to be a hidden group of people and because their evidence is not immediately visible to the general public or that they chose not to discuss it with me personally I wouldn't assume that it doesn't exist.

The whole point is that the question, "What academic research has been conducted to support the 85% recommendation?" has been asked so many times and no-one has come up with a convincing answer, that it seems legitimate to assume that no such academic research has ever been undertaken, no matter what the Caravan Club claims in their statement above. There is certainly no reason why anyone should withhold their findings, if any exist. It cannot be a case of divulging confidential information, if they were published.

 

[Dustydog]

Let's look at this from a pure Risk Management point of view, something close to John's heart.
If a dealer says to me, a customer, I can safely tow my Wyoming with a Ford Focus diesel then I am entitled to believe him , am I not?
The weight differences clearly are a recipe for a disaster. I have an accident and I and my Insurers blame the dealer for negligent advice. His Insurers refuse to indemnify him because in their opinion and general "market" opinions such a combination is fundamentally dangerous. The dealer wont last long in business!
So the poor dealer must have some benchmarks to use in the advice he gives his customers , newbies or not?
Lutz very kindly set out a number of very important issues. However I fail to see what is fundementally wrong with telling a newbie that a 85% weight ratio is a wise move as well as all Lutz's other points. Surely that advice is good Risk Management on the part of the dealer?? The fact 85% is not a rule nor has any tangible proven basis does not mean it is intrinsically incorrect to mention it??

 

[Parksy]

The whole point is that the question, "What academic research has been conducted to support the 85% recommendation?" has been asked so many times and no-one has come up with a convincing answer, that it seems legitimate to assume that no such academic research has ever been undertaken, no matter what the Caravan Club claims in their statement above. There is certainly no reason why anyone should withhold their findings, if any exist. It cannot be a case of divulging confidential information, if they were published.

I disagree with your assertion that the question "What academic research has been conducted to support the 85% recommendation?" has been 'asked so many times' Lutz.

As far as I'm aware the consensus of opinion amongst the majority of touring caravan-related clubs,organisations and publicly available publications would appear to support the findings of the CC that a recommended weight ratio of 85% between the towing vehicle and touring caravan 'will help deliver a safe and comfortable towing experience for drivers of all abilities."

It's obviously true that some members of internet based caravan forums, notably this one, constantly question the grounds for this recommendation but do such a relatively small number of dissenters legitimise their own assumptions that the statement written by representatives of the CC is untrue, especially in the face of the overwhelming body of authoritative opinion which accepts the findings of the CC?

I'm not convinced that the Caravan Club have withheld their findings or withheld the existence of evidence of testing, academic research and member feedback that gave rise to these findings.
Do you have any evidence that this information has been withheld which would support these assumptions?

The fact that a CC spokesperson has not joined this forum and provided the evidence on these message boards which would support either their findings or the truthfulness of their published statement about verification for the benefit of those who question the CC recommendation does not mean that their published statements are not factually correct and based on the research that they have referred to.

The convincing answer as far as I'm concerned is the statement made by the CC, highlighted in blue in my previous posts, which said that the 85% guideline has been verified etc.

I've yet to be convinced that they lied, and much as I respect the opinions of Practical Caravan forum members and greatly value their contributions to all discussions, I'd rather accept the stated recommendation of the Caravan Club and of the Camping & Caravanning Club based on their collective experience.
I will therefore continue when necessary to urge potential purchasers of touring caravans and towing vehicles who appear to lack towing experience to give due regard to the advice offered by those august and reputable organisations within the correct context.

 

[Lutz]

As far as I'm aware the consensus of opinion amongst the majority of touring caravan-related clubs,organisations and publicly available publications would appear to support the findings of the CC that a recommended weight ratio of 85% between the towing vehicle and touring caravan 'will help deliver a safe and comfortable towing experience for drivers of all abilities."

It's obviously true that some members of internet based caravan forums, notably this one, constantly question the grounds for this recommendation but do such a relatively small number of dissenters legitimise their own assumptions that the statement written by representatives of the CC is untrue, especially in the face of the overwhelming body of authoritative opinion which accepts the findings of the CC?

I'm not convinced that the Caravan Club have withheld their findings or withheld the existence of evidence of testing, academic research and member feedback that gave rise to these findings.

What makes you so sure that the 'findings' originated from the Caravan Club? Everything points to an unknown source that thought 85% was 'about right' and this has been passed on through the years and accepted without question by various institutions, including the Caravan Club.
The very fact that none of the sources provide any indication of whether the 85% applies to caravans with or without shock absorbers, for example, although it is well known that they contribute significantly to stability, is reason enough to question the validity of the recommendation.
Even a renowned expert like Prof Jos Darling of Bath University has acknowledged that the time has come to review the 85% figure. However, it would appear that funds are simply not available to carry out the necessary research on the subject so that one can come to a substantiated conclusion.

 

[Parksy]

What makes you so sure that the 'findings' originated from the Caravan Club? Everything points to an unknown source that thought 85% was 'about right' and this has been passed on through the years and accepted without question by various institutions, including the Caravan Club.

The clubs advice included the phrase:
'The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research '
As far as I'm concerned there is no evidence whatsoever to substantiate your supposition that 'everything points to an unknown source'.
The statement from the CC that I have repeatedly highlighted would lead any reasonable person to suppose that, provided the highlighted statement is true, and there is no concrete evidence to suggest that it is untrue, the 85% recommendation, aimed at potential buyers of touring caravans and inexperienced drivers of towing vehicles who may be choosing a towing vehicle, is good advice which was based on 'member feedback, outfit testing and academic research'.
The consensus of popular opinion if Caravan Club membership figures are anything to go by would seem to be that the Caravan Club is a credible and worthwhile organisation.
I'm confident that when the Caravan Club decides that the time has come to amend their advice for newcomers to caravanning in order to take into account the fact that some tourers are now fitted with shock absorbers they will inform their members and the wider leisure caravanning public.
Prof. Jos Darling has carried out valuable research into caravan stability on behalf of Bailey Caravans and it comes as no surprise to me that he has acknowledged that the time has come to review the 85% figure.
It so happens that at the present time the Caravan Club do not appear to agree with him.

 

[Lutz]

Without a referencing the basis for their claim 'The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research ' carries no weight whatsoever. It is a completely hollow statement. If it's a case of believing either Prof Jos Darling or the Caravan Club I am a lot more confident with Prof Darling's view, considering his expertise gained over many years, specifically in the area of vehicle stability.
The extent of work that would be necessary to do some serious investigations is considerable and would definitely challenge the resources of the Caravan Club or any other similar organisation. Without investing at least a six digit sum and full support from a dedicated research institute nothing of any value can be expected from any such 'studies'. The issue is far too complex to be able to come up with a worthwhile conclusion in anything under 6 months of full time work by an assigned group of people. It is definitely a predestined topic for a PhD thesis. Anything less is meaningless waffle.
I would expect something along the lines of the following SAE paper:
SAE Technical Paper 2008-01-1228
Stability and Control Considerations of Vehicle-Trailer Combination
by Aleksander Hac, Daniel Fulk and Hsien Chen
Delphi Corporation

ps: Weight ratio is not even mentioned as one of the parameters that were considered in the above study.

 

[ProfJohnL]

Hello Parksy again!

First a note to any reader. What follows is by its nature long and complex. If you do not want to be baffled, bemused or perplexed don't read it. If you wish to follow the discussion then please read on, and feel free to make constructive points or challenges, but don't bother making fatuous or personal remarks as they will be ignored or marked as offensive and left for the moderators or forum owners to deal with.

I started my reply to parksy's response of Sat, Oct 15 2011, 11:50AM several hours ago, and whilst I've been checking I see several other comments have been left, consequently
some of the point here may already have been made by others.

Yes my first point is subjective as indicated by my phrasing "but It is my distinct impression" However that is how virtually all advancements arise, because someone senses there is an issue that needs further investigation, and clearly in this case I am not alone.

I accept you believe the general advice the industry provides was designed to be a starting point, But given the number of times the matter of towing weights has arisen on forums etc, the clubs have not tried to re-affirm the need for a greater of concern over a wider spread of criteria, as I have usually done.

In reminding forum readers that 85% has no formal basis I and others are trying to break the dogmatic approach to its application and to bring an understanding of what it is actually trying to do.

There is no legal obligation for the committee to respond or to provide evidence of the data or method used to derive the 85% figure, but these days no self respecting scientist or engineer would publish a paper or the results of research of this kind without references so their findings could be independently verified and thus validated.

I cannot possibly believe that any data or methods of analysis used to derive the 85% recommendation could be construed as commercially sensitive 40 years ago, yet alone today. We're not talking about design secrets or sales figures, so what's to hide? Open information is the norm for this type study, and hiding behind a wall of silence certainly produces grounds for concern, as some notable cases have shown e.g. Weapons of Mass Destruction in Iraq, and to a lesser extent the claims made for cold fusion energy, and the Norwich University study on global warming.

It is of course possible the information is available, and I (and others) have not been able to find or identify it. Surely the committee would welcome the chance of having their proclamation validated?

I did allude to the caravan manufacturers biased nature who would like to see an increases in the recommended figure. and I did offer the balancing argument that I don't assume a revisited study would increase the figure it might actually reduce the figure.

I have absolutely no doubt that the clubs do have technical committees. But we do not know the competencies of the committee that came up with 85%. For example - School governing bodies have to have sub committees, but in some cases (and especially with smaller primary schools) the committee members may have no practical or professional competence in the business of the sub-committee - yet it still carries the name and has to deal with a technical brief, so the existence of a particular committee does not guarantee expertise in the subject.

Now Let's consider the CC's statement:
"which has been verified through a combination of member feedback, outfit testing and academic research"

As a professional working in technical matters I would be looking for such a statement to be attributed to a person or at least the committee to which it relates. It is not attributed, so it is most likely the product of the CC's publicity department - warning bell sounds

Looking at the statement, I will assume it is accurate because its written down and if it weren't then it could be legally challenged, and publicity department know that. - But does it mean what you may think it means?

Verification, is simply the process of agreeing something, and even I can agree a statement concerning a recommendation was made but I'm not agreeing the content only the existence of the reccomendation.

"Member feedback" actually only requires one member to have provided feed back and that at best would be subjective.
"Outfit testing", it only requires one single test to agree with the statement.
"Academic Research" it only requires a school child to look something up about the subject to be compliant with the statement.

The above may seem pedantic to the extreme but that is how devious some publicity departments can be journalistic licence and it is used to sensationalise subjects. Now let me be clear I don't expect the CC were that economical with the truth, but if they are asking us to accept the statement they need to be far more specific and provide meaningful and verifiable relevant facts.

You only need to look at how much advertising utilises the bare minimum of facts or verifiable evidence, Remember the Whiskers cat food adverts it used to say 9 out of 10 cats preferred Whiskers, now they have to say 9 out 10 cat owners who expressed an opinion preferred whiskers.

Or the mobile phone and broadband companies who advertise on the TV, fantastic offers for new customers, but you have to look at the small print on the bottom of the screen to see things like the offer is limited new customer only, or offer for 3 months only, Line rental extra minimum contract 18months etc etc etc.

These days you cannot accept anything commercial at face value.

My comments regarding skewing data or outcomes were in my paragraphs where I made historic comparisons. It was not my intention to suggest the CC deliberately skewed outcomes, But until the committee opens up and provides the evidence that it can't be entirely ruled out. But as it stands how do we know they are offering the right or best advice?

I have no specific evidence the committee is being secretive, but neither have they been particularly proactive in supporting their recommendations, either when they first made them or in recent years where the question has arisen.

 

[Parksy]

Without a referencing the basis for their claim 'The Club is currently happy with the 85% guideline, which has been verified through a combination of member feedback, outfit testing and academic research ' carries no weight whatsoever. It is a completely hollow statement. If it's a case of believing either Prof Jos Darling or the Caravan Club I am a lot more confident with Prof Darling's view, considering his expertise gained over many years, specifically in the area of vehicle stability.

The statement that I highlighted forms part of the Caravan Club advice to new caravanners and it is not presented in the form of a scientific document or a thesis.
I've no doubt that Prof. Darling's expertise was gained over many years, the Caravan Club was founded in 1907.

The issue is far too complex to be able to come up with a worthwhile conclusion in anything under 6 months of full time work by an assigned group of people. It is definitely a predestined topic for a PhD thesis. Anything less is meaningless waffle.

That would appear to be your opinion rather than a statement of fact.

I would expect something along the lines of the following SAE paper:

SAE Technical Paper 2008-01-1228

As well you might Lutz but wouldn't you consider such a paper a tad heavy for an informal and welcoming website article entitled Caravanning ....... Matching Your Outfit ?

...Yes my first point is subjective as indicated by my phrasing "but It is my distinct impression" However that is how virtually all advancements arise, because someone senses there is an issue that needs further investigation, and clearly in this case I am not alone.

I accept you believe the general advice the industry provides was designed to be a starting point, But given the number of times the matter of towing weights has arisen on forums etc, the clubs have not tried to re-affirm the need for a greater of concern over a wider spread of criteria, as I have usually done.

In reminding forum readers that 85% has no formal basis I and others are trying to break the dogmatic approach to its application and to bring an understanding of what it is actually trying to do.

Well you are not alone on this forum, you have at least one person who agrees with your stance but as I've pointed out, the overwhelming majority of clubs, caravanning organisations and publications do not appear to wholeheartedly share your concern.
My contention is that the 85% general recommendation forms only a very small part of the advice made available to CC members and the wider caravanning public and does not claim to have a formal basis in the way that it is presented on the CC website. The wider spread of criteria that you mentioned is provided within this general advice to caravanners.
I consider that at times your attempts on this forum to break the so-called dogmatic approach that you appear to find so difficult to deal with may create confusion, uncertainty or indifference at times amongst new forum members seeking advice.

There is no legal obligation for the committee to respond or to provide evidence of the data or method used to derive the 85% figure, but these days no self respecting scientist or engineer would publish a paper or the results of research of this kind without references so their findings could be independently verified and thus validated.
I cannot possibly believe that any data or methods of analysis used to derive the 85% recommendation could be construed as commercially sensitive 40 years ago, yet alone today. We're not talking about design secrets or sales figures, so what's to hide? Open information is the norm for this type study, and hiding behind a wall of silence certainly produces grounds for concern, as some notable cases have shown e.g. Weapons of Mass Destruction in Iraq, and to a lesser extent the claims made for cold fusion energy, and the Norwich University study on global warming.
It is of course possible the information is available, and I (and others) have not been able to find or identify it. Surely the committee would welcome the chance of having their proclamation validated?

The Caravan Club have not offered their advice in the form of a scientific paper or thesis so why would they include references, it's an informal website article.
Once again, because you either have not found data to support the CC recommendation or have been denied access to it your assumption appears to be that the CC are hiding something.
The CC have stated that their information has been verified John, they just haven't consulted either Lutz or your good self by the look of things.

....I have absolutely no doubt that the clubs do have technical committees. But we do not know the competencies of the committee that came up with 85%..............
........ the existence of a particular committee does not guarantee expertise in the subject.

As far as I'm concerned it's a safe bet that the CC know what they are talking about in respect of caravans and my view appears to be shared by other clubs, organisations etc; as previously mentioned.

Now Let's consider the CC's statement:
"which has been verified through a combination of member feedback, outfit testing and academic research"

As a professional working in technical matters I would be looking for such a statement to be attributed to a person or at least the committee to which it relates. It is not attributed, so it is most likely the product of the CC's publicity department - warning bell sounds

Looking at the statement, I will assume it is accurate because its written down and if it weren't then it could be legally challenged, and publicity department know that. - But does it mean what you may think it means?

Verification, is simply the process of agreeing something, and even I can agree a statement concerning a recommendation was made but I'm not agreeing the content only the existence of the recommendation.

See Oxford Dictionary definition of the noun: verification
See also Oxford Dictionary definition of the verb: verified which is the actual word used in the text that I quoted earlier.
The dictionary definition does not correspond with your own definition John

"Member feedback" actually only requires one member to have provided feed back and that at best would be subjective.
"Outfit testing", it only requires one single test to agree with the statement.
"Academic Research" it only requires a school child to look something up about the subject to be compliant with the statement.

...The above may seem pedantic to the extreme but that is how devious some publicity departments can be journalistic licence and it is used to sensationalise subjects. Now let me be clear I don't expect the CC were that economical with the truth, but if they are asking us to accept the statement they need to be far more specific and provide meaningful and verifiable relevant facts.

At the risk of repeating myself the CC would have appeared to have provided enough verifiable relevant facts to persuade other clubs, organisations etc to concur with their general recommendation John.
They are surely not required to make available such factual evidence to any ordinary member of the public who happens to express an interest?
Do you know of any commercial profit making organisation that would be willing to do this?
I can't think of any offhand.

........These days you cannot accept anything commercial at face value.
......My comments regarding skewing data or outcomes were in my paragraphs where I made historic comparisons. It was not my intention to suggest the CC deliberately skewed outcomes, But until the committee opens up and provides the evidence that it can't be entirely ruled out. But as it stands how do we know they are offering the right or best advice?
I have no specific evidence the committee is being secretive, but neither have they been particularly proactive in supporting their recommendations, either when they first made them or in recent years where the question has arisen.

I'd agree with you that as far as caravan related websites or internet forums are concerned neither club has been very pro-active in any respect.
One cannot blame the CC for looking after it's own members interests and for not entering into discussions on caravan internet forums.
It is highly unlikely that evidence which would support any statement made by either the CC or the C&CC would be posted on the message boards of a caravan forum.
Those who pay to join such clubs take many things on trust but the trust is based on the reputations of these organisations.
The contentious advice regarding the 85% figure offered to those considering choosing a new outfit actually states:
As a newcomer to caravanning, you would be
wise to stick to the generally recommended
guideline of towing a caravan weighing no more
than 85%
Nowhere does it imply that this figure is mandatory or to be regarded as a limit and as you can see and as I have previously pointed out the guideline is primarily intended for newcomers to caravanning.
The guideline forms only a minute part of the 14 internet web pages of advice for caravanners offered by the CC.
For the sake of brevity and simplicity I haven't referred to similar advice offered by the C&CC.

 

[Lutz]

I would just like to add that whatever 'testing and academic research' the Caravan Club may have conducted, it cannot have been very thorough or else they would have qualified their advice. If not even respected researchers are in a position to give us an answer I don't know what useful information can be gained from 'member feedback'. Their statements sound very amateurish.
Of course, the SAE paper is not the sort of information that is of much use to the general caravanning public. However, putting the conclusions contained therein or in other research papers into plain simple terms is something that can be expected from the Caravan Club and one would expect them to reference their source to make it possible to verify their advice. This is accepted good practice. If someone offers you advice or a recommendation I think you have a right to know what was the basis for such advice or the reasoning behind it.
As for comparing the expertise of the Caravan Club with that of Prof Jos Darling on the grounds that the Caravan Club was founded in 1907, one must allow the question who at the Club has ever been involved so deeply in the subject as the said Prof or people like M.A. Alonso Fernandez and R.S. Sharp of Cranfield University in their paper entitled "Caravan Active Braking System - Effective Stabilization of Snaking of Combination Vehicles"? Much of the mathematic modelling that is part of the analysis was not even possible before the advent of the computer, so investigations couldn't even have started until the early 70's, at the very earliest. Bringing the year that the Caravan Club was founded into the argument is really a bit steep.