Maintaining the 85% rule.
Comments
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Over the years caravans have got much heavier. A 1995 Swift Corvette Diamond MTPLM 1060Kg. My current 2007 Abbey Vogue ( comparable size - mid range spec) 1350Kg. That's a 27% increase in weight.
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Funny you mention your 2007 caravan as the EU fleet average CO2 legislation due in 2020/21 sets a 60% reduction based on a 2007 baseline. This was thought to be easily achieveable by 'refining' systems and adding stop start technology etc. However, post the VW issues it would seem changes will need to be more drastic. So if caravans are getting heavier due to more 'goodies' being added what is the outcome?
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The outcome will be people wanting to get rid of the 85% safety guidance because it becomes "inconvenient"
It's not only inconvenient, but it's meaningless, too, without and further qualifications. I can find no source anywhere that states under what conditions 85% is recommended, just a blanket reference to that figure, apparently applying to all outfits. Such
a statement is unprofessional.0 -
I was giving an honest answer to the question put by Mr H
You know the source of the 85% guidance as well as I do. A concensus between both club's technical departments. I suggest if you disagree you contact both UK clubs and ask them to change the guidance.
Of course you will have to provide suitable credible scientific evidence to back the request.
Personally I have never seen evidence to suggest that 85% is not a valid safety margin
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I was giving an honest answer to the question put by Mr H
You know the source of the 85% guidance as well as I do. A concensus between both club's technical departments. I suggest if you disagree you contact both UK clubs and ask them to change the guidance.
Of course you will have to provide suitable credible scientific evidence to back the request.
Personally I have never seen evidence to suggest that 85% is not a valid safety margin
I'm not saying that it's not valid, but under what conditions is it valid? Without any further qualifications it is meaningless.
Just as a for instance, is it valid for caravans with shock absorbers and those without? If it doesn't differentiate, it's not worth the paper it's written on.
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Can and do see your point but with empirical evidence going back decades it's unlikely that 85% will be changed without extensive research.
At the end of the day, the guidance is what it is and it's up to the individual to decide to comply or to convince themselves it's OK to disregard it. Probably because they want too big a caravan for their car to pull
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I would really like to know on what empirical evidence the 85% recommendation is based on, as I would like to point out that the weight ratio limit for trailers (including caravans) in Germany is only 30% if shock absorbers are not fitted and 80% if there is no form of stabiliser. Otherwise, it's 100% for caravans and 120% for other types of trailer. Surely, someone must have done some homework to come up with such a limit (and it's not a recommendation, but the law)?
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I agree with your comments Fysherman, though it doesnt help with car manufacturers claimng their 4x4's can tow upto 3500kg The amount of people on other forums who will argue blacks blue that their car is ok towing very large heavy caravans because of these
claims.0 -
I totally agree with that 100%.
On the caravan chat forum a chap was given a print out from Tow Safe that used this figure and the caravan salesman used it to to tell him his octavia would easily tow a big Unicorn.
All the best won't be on now until tomorrow or Monday.
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I agree with your comments Fysherman, though it doesnt help with car manufacturers claimng their 4x4's can tow upto 3500kg The amount of people on other forums who will argue blacks blue that their car is ok towing very large heavy caravans because of these
claims.The car manufacturers don't normally differentiate between caravans and any other type of trailer. Their limits are absolute without regard for any particular type. If they quote a 3500kg max. towload, that doesn't mean that it would be wise to take full
advantage of the limit for a caravan although it might be quite in order for a low loader trailer.0 -
I am interested by the German figures mentioned by Lutz - and the differentiation between caravans and "other" trailers. I expect that will be based on wind loading, something that is not taken into account by those with small car issues. The wind, of course,
being provided by both nature and the passage of HGVs.0 -
I am interested by the German figures mentioned by Lutz - and the differentiation between caravans and "other" trailers. I expect that will be based on wind loading, something that is not taken into account by those with small car issues. The wind, of course, being provided by both nature and the passage of HGVs.
It's not so much the wind, although that isn't to be discounted, but more that caravans have a relatively high polar moment of inertia, which means that once they get into an unstable condition, a great deal more effort is required for them to recover. A low loader carrying a car, for example, is much easier to straighten up again because a greater proportion of its mass is concentrated around the axle.
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Actually it is my fault. I headed the post wrongly. I should never have mentioned the 85% rule. The crux of my post should have been directed more towards the fact that cars a being manufactured to be significantly lighter with some having a 1.0 litre engine capable of producing more power than a much heavier 2 litre. They are using newly developed lightweight steels for the chassis etc. As I cannot see the caravan industry being able to follow suit, at least in the short term, I am genuinely wondering what affect the changes will have on towing caravans. What effect will the movement towards regenerated energy (harvesting whilst the car is slowing) have? If the move is more towards Hybrids will the battery life be sufficient? Will secondhand deisels increase in value due to rarity?
...believe it or not. Dethleffs are producing MH for this new season using compressed 'balsa wood' (obviously not like our childhood planes....
) for their interior furniture.......now, this is a highly respected member of the Hymer group, who have a real desire to 'save weight', even using hollow locker handles to save a few grammes....
the desire and the innovation is certainly alive and well in some parts....can the uk caravan industry get their act together too...?
Write your comments here...balsa is a hardwood I believe
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Get the right set of circumstances coming together and even 85 percent won't be enough to a prevent a visit to A&E.
It is however a good starting figure. Not to go towards 90% but towards 80%
IMHO of course.
I'd challeange anyone to be able to tell the difference between the way an outfit handles at 90% compared with 85% or between 80% and 85%. The changes are so gradual that one would have to have a variance of at least 10% before one can detect anything, always
assuming that all other criteria remain equal. And there's the rub. Because so many other factors determine the stability of an outfit, one can remain perfectly docile at 100% whereas another can be a pig to handle even at 70%, if something major else is
wrong.Personally I don't even bother to work out my weight ratio. I stick to what is legal and, more important, what I think I'm capable of handling safely, regardless of weight ratio.
I think the problem is not wether you can detect the difference in normal towing but what happens when you are faced with an emergency. At that point you find out if your towing ratio is good enough but if not then it is too late. There is no real doubt
that the better the ratio is the safer the outfit but I accept that there is no magic figure and no wzy to be sure you have got it wrong. If it is badly wrong I think you will s oon know but for the rest of us it is zensible to have a decent safety margin.Having dealt with accidents in my work all I can say is that any rollovers I have co e across involved outfits with a ratio exceeding 85%, usually by considerably more but the numbers are simply not enough to draw very firm conclusions.
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There are plenty of videos on the You tube of Land Rovers towing fully laden 40' articulated vehicles, including the tractor unit. I know they are not fake as I've done it myself to help clear an obstruction. That is pulling about
fifteen times its own weight.I hope it is obvious to all that this is impractical on a day-to-day basis, so where do the "over 85%" people call a halt? At 95%? 105%? 115%? or just ignore it and thrash on anyway? I know the ratio on my outfit is around 60% yet I am still very aware
of the presence of a trailing mass.0 -
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I hope it is obvious to all that this is impractical on a day-to-day basis,
so where do the "over 85%" people call a halt? At 95%? 105%? 115%? or just ignore it and thrash on anyway? I know the ratio on my outfit is around 60% yet I am still very aware of the presence of a trailing mass.Gross train weight as stated on the car perhaps
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The very fact that the subject is being discussed is an indication of how questionable the 85% figure is. If there really were substaniated results to back up the récommendation we wouldn't be discussing it, but accept it as proven.
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Actually it is my fault. I headed the post wrongly. I should never have mentioned the 85% rule. The crux of my post should have been directed more towards the fact that cars a being manufactured to be significantly lighter with some having a 1.0 litre engine
capable of producing more power than a much heavier 2 litre. They are using newly developed lightweight steels for the chassis etc. As I cannot see the caravan industry being able to follow suit, at least in the short term, I am genuinely
wondering what affect the changes will have on towing caravans. What effect will the movement towards regenerated energy (harvesting whilst the car is slowing) have? If the move is more towards Hybrids will the battery life be sufficient? Will secondhand deisels
increase in value due to rarity?...believe it or not. Dethleffs are producing MH for this new season using compressed 'balsa wood' (obviously not like our childhood planes....
) for
their interior furniture.......now, this is a highly respected member of the Hymer group, who have a real desire to 'save weight', even using hollow locker handles to save a few grammes....
the desire and the innovation is certainly alive and well in some parts....can the uk caravan industry get their act together too...?
Write your comments here...balsa is a hardwood I believe
...not sure of its other properties, other than its lightness...
in fact, my memory is now telling me that its Frankia that are using this technique, rather than Dethleffs......
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The very fact that the subject is being discussed is an indication of how questionable the 85% figure is. If there really were substaniated results to back up the récommendation we wouldn't be discussing it, but accept it as proven.
I am not sure that there is any way of proving it as the safe limit for any combination must vary according to the chatacteristics of both halves. 85% is simply a good starting point for newcomers based on experience and some work by the University of Bath and it is a foolish newcomer who exceeds it by any great amount.
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The very fact that the subject is being discussed is an indication of how questionable the 85% figure is. If there really were substantiated results to back up the récommendation we wouldn't be discussing it, but accept it as proven.
I am not sure that there is any way of proving it as the safe limit for any combination must vary according to the chatacteristics of both halves. 85% is simply a good starting point for newcomers based on experience and some work by the University of Bath
and it is a foolish newcomer who exceeds it by any great amount.85% is a very specific value, though. Any newcomer could be mislead into thinking that there is something very special and scientific about it. Why not just advise keeping the caravan as light as possible compared with the weight of the towcar? That would
surely serve the same purpose and wouldn't give a newcomer the impression that he will fall into a great big hole of certain disaster if his weight ratio were 86%.That said, there is no equivalent recommendation on the Continent other than staggered legal weight ratio limits in Germany, depending on how the caravan is equipped technically, and yet one doesn't see overturned caravans littering the roads despite common
practice of making full use of the manufacturers' towing limits, even if these go up to and in some cases over 100%.0 -
In terms of mileage I have towed more abroad than here in the UK. In all that mileage I have yet to see a single caravan incident sur le continent. Whilst travelling to Austria last month the c/van incident we did see was on the M25 with a jacknifed Citroen
C5 and Sprite 4b combination...... We probably towed at around 92-3% and drove robustly' (keeping it on the speed limits as much as possible) without knowingly triggering the ATC. Observing towing
combinations in the good 'ole EU over my limited experience tells me they just about observe the law, albeit the Italians appear to have a different measure of weight to the rest of Europes caravanners....0 -
In France our observation are few know, and if they do know don't want to know the speed limit there when towing even a camping trailer with a vehicle having a GTW over 3500 kgs.
But then those that do can be a rolling road block on a nice fast free flowing single carriage way
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