85% debate continuation

[Gafferbill]

I would contend that all vehicles that have been certified for towing make adequate and safe towing vehicles for caravans.
That is why the manufacturers and UK law allows them to do so.
To elaborate ........if the caravan is light enough and it's length proportional there will be a caravan on the market suitable and safe for that particular car to tow.
The problem is matching the car to a suitable caravan.......or a caravan to a suitable car!
In the absence of the prohibitively expensive testing of various car caravan combinations, how is a relatively unacknowledged potential owner able to decide on a sensible combination.
I would have thought it reasonable to consider the Maximum Mass of the caravan and compare it to a non variable, easily obtained kerbweight of the tow car knowing full well that the tow car will almost always be heavier.
Equally reasonable to err on the side of caution and advise a combination where the tow car is 15% heavier than the caravan.
Once the owner has a match he can then carry out all the other prudent variables to increase safety..............tyres and their pressures, loading, maintenance and keeping speed suitable for the conditions.

As with most limits or restrictions (especially if only advice) it is always human nature that some will argue against them and or ignore them.

 

[JezzerB]

Yes, the fact that the advice appears to many of us to be assumption and not based on proper research, then people will argue,. It is sensible and well meaning advice perhaps but when there is only assumption and no proper research-just seat of the pants type advice then confusion will reign and many people don't read advice and never have any issues from what I understand. What it needs as Prof says is proper research, but given the cost unless the DVLA or a very large organisation got into it then it won't happen.

 

[otherclive]

I just don’t think that it is economically feasible to conduct a research programme that would be able to feature results that folks would use or even read. As others have said there are too many variables across all of the parameters to be able to elicit useful results. If such a programme were undertaken its timescale would be such that car and caravan technology would have inevitably moved on. I cannot envisage any company having the resources to fund such work Most caravan builders are probably finding today’s market place tough enough as it is.
If caravan stability accidents were a cause for concern I am sure DVSA would be looking into them. But not in any research orientated way, more what do we need to do to reduce these accidents. Their obvious answer would probably be a blanket speed restriction of 50 mph. But since the incidence of serious caravan accidents from instability is low I for one don’t want DVSA to spend taxpayers money when there are numerous other areas which would show higher cost benefits.

 

[Lutz]

We thought it would cost considerably more than that if it were to be thoroughly carried out.

You are probably right. Mine was, I am sure, a very conservative guess.

I would have thought it reasonable to consider the Maximum Mass of the caravan and compare it to a non variable, easily obtained kerbweight of the tow car knowing full well that the tow car will almost always be heavier.

Unfortunately, an actual and accurate kerbweight figure is very difficult to obtain. Kerbweight is specific to each and every car so a published figure, whether in a handbook, database or brochure can be nothing better than a rough guide. An accurate figure would have to be linked to the corresponding VIN.
Kerbweight is not documented anywhere. Manufacturers are not under any obligation to provide it. On top of that, many manufacturers quote what they call kerbweight, but on closer reading they actually mean mass in running order and that is something different.

 

[ProfJohnL]

Hello Gaffer,

I would contend that all vehicles that have been certified for towing make adequate and safe towing vehicles for caravans. .

That is an assumption, and the very evidence of your following comment, its one that you don't believe, becasue you are seeking to qualify the statement by adding by choosing a caravan that is less than the car manufacturers towed weight allowance specification.

That is why the manufacturers and UK law allows them to do so.
To elaborate ........if the caravan is light enough and it's length proportional there will be a caravan on the market suitable and safe for that particular car to tow.
The problem is matching the car to a suitable caravan.......or a caravan to a suitable car!
.

You go on to essentially reiterate the present day Industry 85% guidance, so the question is why have you decided that a 15% weight differential is the correct figure to choose? What evidence have you used to confirm that an 85% ratio is the optimum figure to use?

As Lutz has pointed out Kerbweight is far from being a correct or even available figure so its not a sound basis for a comparison.

I'm not against having a ratio figure as part of a package of advice to suggest to novices, but it needs to be demonstrably sensible and to ensure that it make the driver aware that there are be other factors that are equally if not more important than just a weight ratio.

 

[Gafferbill]

Prof........I have argued that the current guidelines are reasonable and sensible as a guide and that I go along with them as an active caravanner who has already towed 1500 hundred miles this year and will probably tow 5000 miles this year in total.
You do not tell me what criteria I should follow to replace my 85% towing ratio.
By the way I had no difficulty finding the kerbweight of my vehicle.
Can you come up with some constructive guidance for those of us that actually tow or for those new to towing?
You have suggested in past posts over the years, that the lighter the trailer(caravan) the better, as far as safety is concerned.........have you changed your mind?

My adherence to the 85% guideline is based on 65 years of towing trailers and experiencing first hand the dangers involved.

 

[Lutz]

By the way I had no difficulty finding the kerbweight of my vehicle.

I really would like to know where you managed to find the kerbweight of your vehicle. I don't know of any source that will quote the kerbweight for the corresponding VIN other than if you have managed to access an entry under item 13.2 in the CoC for that vehicle. Even that isn't strictly the same as kerbweight, as defined in UK legislation, but it's about as close as you'll get.

My adherence to the 85% guideline is based on 65 years of towing trailers and experiencing first hand the dangers involved.

I really wonder how your first hand experience has enabled you to establish that weight ratios were the direct cause of the accidents that you presumably witnessed and not driver error, for example.

 

[camel]

If I weigh my car on a weighbridge what weight do I call that,

 

[Hutch]

Lutz, you should re read Gafferbills posting. He is stating his experience of towing gives him a lot of of credence towards the dangers. , but states nothing about, statistics of accidents.

 

[Lutz]

If I weigh my car on a weighbridge what weight do I call that,

If you weigh it in accordance with the definition of kerbweight, that's what it is. Otherwise I suppose one would call it established weight. It wouldn't necessarily be the same as the actual weight as defined in the regulations, so one couldn't call it actual weight.

Lutz, you should re read Gafferbills posting. He is stating his experience of towing gives him a lot of of credence towards the dangers. , but states nothing about, statistics of accidents.

But his reference to the 85% ratio recommendation does suggest that he sees a direct correlation between weight ratio and the dangers that he has encountered,

 

[ProfJohnL]

Hello Gaffer,
I think others have covered most of the points in your comment, but you ask:-

....
Can you come up with some constructive guidance for those of us that actually tow or for those new to towing?
You have suggested in past posts over the years, that the lighter the trailer(caravan) the better, as far as safety is concerned.........have you changed your mind?
....

One of the reasons I started this thread was to try and explore an alternative way of offering caravanners useful guidance which did not just cover weight ratio's but also covered things like legal compliance and improving safety.

So far we have failed to find a catch all solution, which only goes to show how complex the subject is.

I still maintain that good towing is achieved by keeping vehicles in good condition, ensuring that no weight limits are exceeded, an that a sensible loading strategy be employed to ensure the trailer is as light as possible but still produces enough nose load to keep the outfit stable. To drive to the prevailing road conditions, and to use good driving skills especially bearing in mind the effects of additional size and weight has on vehicle performance.

In particular the biggest single factor that affects stability and many other safety related issues is speed. Slower is definitely safer and I am certain it has a bigger effect that weight ratios alone.

Because of the type and number of variables that affect towability, There are plenty of people who have managed perfectly well with ratios up to and over 100%, but also there have been plenty of incidents (not necessarily reported) where outfits at less than the advisory limit have proven to be unstable therefore I cannot accept that a one size 85% advisory ratio fits all outfits.

I Think you will see I have not changed my mind.

 

[Mike]

At the end of the day, we either choose to take 'advice' on board, and act accordingly, or we don't. As regards towing, one can become unstuck despite heeding the 'advice', or, go through life without incident, while completely ignoring any advice. Its life. And as pointed out earlier, whatever the majority of caravanners are doing; heeding or ignoring, the roads have very, very few upturned caravans as a result.
A mate of mine is always, - worryingly for me, way too overloaded. The only thing he does not pack, is the kitchen sink. Its a good size 'van, his car isn't massive, he doesn't crawl along at 40mph, yet he has never, ever come unstuck. And this is after years driving around the UK and abroad, in all weathers. Not for a second do i condone this, but maybe we are just 'worrying' too much?

 

[Gafferbill]

Lutz lives in Germany where the government has legislated to restrict all UK caravans to 80 kph (and most others)........it has presumably decided that UK caravans are unsafe above this speed! That is their approach to safety...... 79kph is safe and legal............81 kph isn't.
IMO the UK government is very hands off when it comes to caravans and this is the main reason towing organisations have come up with recommendations.
They deem (as I do) that manufacturers towing limits are too generous to be safe.

......as an aside interesting to note that being over 70 the UK government granted me a driving licence such that I can tow with an outfit weighing up to 7tons.
However, if I am not towing I am restricted to 3.5tons!

 

[Mike]

Lutz lives in Germany where the government has legislated to restrict all UK caravans to 80 kph (and most others)........it has presumably decided that UK caravans are unsafe above this speed!

To clarify; this is UK built caravans, or any caravans that are being towed by UK registered vehicles?

 

[Parksy]

.....One of the reasons I started this thread was to try and explore an alternative way of offering caravanners useful guidance which did not just cover weight ratio's but also covered things like legal compliance and improving safety.

So far we have failed to find a catch all solution, which only goes to show how complex the subject is......

If a catch all solution to whatever you think that the problem is was available, I would imagine that the two main clubs or people who first recommended the 85% car / caravan ratio would have offered it long ago.

There are so many different combinations of towcar / caravan outfits available that there will never be one set of advice that would cover all permutations.
All that any of us can do is to take note of the advice, recommendations and laws that are currently available, a few random people giving anecdotal 'evidence' on a caravan forum are highly unlikely to come up with anything better.
Attempts to discredit the 85% figure taken with other advice for those new to towing are i.m.o. wrong headed and potentially misleading unless anyone has anything significantly better to offer, which they clearly don't if this thread is anything to go by.
There is nothing complex about following the advice that currently exists.
There are many magazine articles and website data pages that explain quite clearly to the novice and veteran alike how to work out a safe and legal towing weight ratio, and although every summer has it's share of caravan related traffic incidents often caused by drivers who never bother to look for advice, touring caravanners are proven through insurance company statistics to be among the safest and most responsible road users in Britain.

 

[JTQ]

German restricts its own caravans to 80 kph, unless they are certified technically to be able to go up to 100 kpm.
Part of that technical certification is the inclusion of suspension dampers, a feature far from all UK vans were fitted with. IMO another important technicality influencing towing stability, of which studying the mass ratio gives no insight. The lack of dampers being a very good reason though to be worried about towing a too heavy van.

Just as Germany, we have a towing speed limit, where as you chose to say under it is safe, over it is unsafe. Neither country adopt a grey range, they both select a specific speed.

On reaching the age of 70 towing or otherwise on a basic licence you are limited to driving a vehicle up to 3500 kgs; towing or not now makes zero difference.
Whatever you tow with, you can go up to the plated GTW of that setup, provided you actually keep below 7 Tonnes, now.
There are no differences if you tow or not, you are limited to drive a vehicle of up to 3500 kgs.

 

[Lutz]

Lutz lives in Germany where the government has legislated to restrict all UK caravans to 80 kph (and most others)........it has presumably decided that UK caravans are unsafe above this speed! That is their approach to safety...... 79kph is safe and legal............81 kph isn't.
IMO the UK government is very hands off when it comes to caravans and this is the main reason towing organisations have come up with recommendations.
They deem (as I do) that manufacturers towing limits are too generous to be safe.

......as an aside interesting to note that being over 70 the UK government granted me a driving licence such that I can tow with an outfit weighing up to 7tons.
However, if I am not towing I am restricted to 3.5tons!

There is no legislation in Germany that limits UK built caravans to 80km/h. Any caravan can be granted a concession to tow at 100km/h subject to fulfilment of the following technical conditions:

1. The towing vehicle must be equipped with ABS
2. The caravan must be equipped with a hitch stabiliser OR the caravan or the towing vehicle with an electronic trailer stabilising system (e.g. ATC in the case of the caravan or ESP+ in the case of the car)
3. The tyres of the caravan must be no more than 6 years old and have a speed rating that allows 120km/h
4. If the caravan is fitted with dampers, the weight ratio must not exceed 100% (without dampers - 30%). Different (higher) weight ratio limits apply to trailers other than caravans.
5. The noseweight must be set at the top limit applicable to the car and caravan, respectively, whichever is the lower.

The driving licence restrictions are common throughout the EU and the UK.

 

[Raywood]

I am not sure speed is the biggest factor in safety, but every outfit does have its limits on that subject, so if you find the outfit getting twitchy then back off. Most legal outfits should be stable up to the speed limits if all other factors are correct but getting there is more important than when you arrive.
I think safe weight ratios vary from outfit to outfit which is a real problem, but safe loading is certainly a very high priority, nose weight can be a problem if very low or high, but I am not sure how big a problem this is for most people. Some models do have nose weights when empty that are far too high although light ones seem rare so you do need to check this.
Essentially you have to be aware of all the factors involved in safe towing and obey them all for the best result and I would not like to list them in order of importance as this may not be constant.

 

[JezzerB]

Nicely put Ray. It is a multifacetted phenomena, and there are so many variables to take in to account-the German requirements are very interesting though and seem to make a lot of sense, though our outfit at 113% didn't have ATC or shock absorbers and was amazingly stable-we do load very carefully though! And i am a fastidious tyre monitor!

 

[JTQ]

So far we have failed to find a catch all solution, which only goes to show how complex the subject is.

Sorry to state the blindingly obvious as I know you know, but there can never be a "catch all solution" that does not box you into under exploiting the abilities of many vehicles and units.
That's the innate "failing" of the 85% ratio, it puts you into a generally safe area, but over restricts the adoption of the abilities of the better vehicles out there, and at the same time does not protect from the really bad vehicles.

As I have said, it needs consideration of the vehicle you are planning to use how you can ease up above the 85% ratio. The skill to make that judgement whilst not likely to be held by the uninquizative virgin tower, ought IMO to be accessible from reputable caravan dealers. Finding the latter in this game might be challenging, but forums and our clubs could also do a lot to guide.

 

[JTQ]

Speed plays two big cards, the first is the energy involved when things go pear-shaped is proportional to speed squared, and its dissipating energy that actually hurts.

Speed also narrows the speed band between being stable and hitting one of the combination's natural frequencies, the "snake".
Below that speed you can still encounter a short term disturbance to excite the natural frequency and have a nasty few seconds, but as you are travelling below its inherent instability speed it ought to self damp, post the disturbance.

Increase speed you will ultimately find that natural snaking frequency, then you have climbed up a square law on the energy available to really smash things up.

 

[ProfJohnL]

Sorry to state the blindingly obvious as I know you know, but there can never be a "catch all solution" that does not box you into under exploiting the abilities of many vehicles and units.
That's the innate "failing" of the 85% ratio, it puts you into a generally safe area, but over restricts the adoption of the abilities of the better vehicles out there, and at the same time does not protect from the really bad vehicles.

As I have said, it needs consideration of the vehicle you are planning to use how you can ease up above the 85% ratio. The skill to make that judgement whilst not likely to be held by the uninquizative virgin tower, ought IMO to be accessible from reputable caravan dealers. Finding the latter in this game might be challenging, but forums and our clubs could also do a lot to guide.

I think were are close to agreement on this one, The present advice is far too simplistic and fails to take into any account the vehicles technical abilities. Its a blanket figure with as yet no evidence as to how it was chosen. I personally have towed many different outfits more than I'd care to remember, but the sum of experience tells me that no universal suggested weight ratio as we currently have can give any caravanner a rock solid tow every time. Some outfits that on paper should be easy some times prove to be difficult, and others where extra caution might be expected turn out absolutely fine.

I cant' claim to be able to quantify the differences accurately enough to produce a universal solution on my own, But I can't help feeling there should be a way to use reliable technical information which we now get as a matter of course through the type approval process, to produce a calculation that points caravanners in the right direction.

Sadly I think it needs to be a bit more involved than just dividing two weight figures.

I'm not naive about the probability that what ever form advice takes, someone will find a flaw in it.

I totally agree that there are many towing journeys that do take place without issue, and they must cover the whole gambit of weight ratio's, so it just add fuel to the unreliability/irrelevance of the present advice. No I'm not suggesting totally ignoring weight ratio's.

As giving the task to dealers, I'd be reluctant without there being a formal process to follow It will lead to opinions being challenged "A said, B said" and how do you know when you have a reputable dealer? But then if such a process was web based, the caravanner could do it themselves with an online spreadsheet where the caravanner has to find all the relevant data.

Its not to far away from some of the matching sites that already exist, but the problem is some of the data bases they use are either incomplete or some entries have errors in the data.

What really bothers me is when the 85% guidance is used becasue its traditional rather than becasue its proven to be right and when its used as a precise target to be hit at all costs and yet other legal issues are brushed under he carpet.

 

[camel]

Prof,
I do agree in what you say you have written many posts on this subject and I find it annoying when no one from the caravanning industry or the NCC don't get in touch with you to discuss this issue, I'm afraid in my experience that the caravan sales people that I have come in to contact with want to learn their subject ie, caravan matching fortunately I have never had this problem because they start to listen to me when I start boring them on outfit matching,

 

[Parksy]

What really bothers me is when the 85% guidance is used becasue its traditional rather than becasue its proven to be right and when its used as a precise target to be hit at all costs and yet other legal issues are brushed under he carpet.

The 85% figure has not been proven to be wrong either.
I haven't seen any advice to novice towcar drivers from officially accepted sources which state that 'the 85% ratio is a precise target to be hit at all costs' when 'other legal issues are brushed under the carpet'.
In fact the only evidence that I've seen of the 85% figure being regarded as a cast iron figure is on this forum in this and similar discussions where it is often implied that the aforementioned advice is said to be sacrosanct in order to attempt to prove a point.
If you could provide a URL link to a current piece of official advice to new touring caravan owners in which the 85% guidance is: 'used as a precise target to be hit at all costs and yet other legal issues are brushed under he carpet' I'd be more than happy to contact the authors myself to point out the error of their ways.
It's ok to discredit it if you can come up with something better, but so far nobody has.
The 85% figure is a basic starting point to be taken into consideration with other advice by those new to towing touring caravans.
It never has been a standalone figure for universal use because experienced caravanners will be able to make up their own minds based on their experience.

 

[ProfJohnL]

Hello Parksy

It seems I did not express my self clearly enough.

I was referring to caravanners who have posted questions or points, and there have been several across the years where they have obsessed about achieving an 85% match but then have openly couldn't care about to other legal issues such as speeding, using phones, or driving without seatbelts etc.

I'm not against having some form of advice to help caravanners choose an outfit. But when we have had someone who used the industry advice and put together an outfit (I think it was behind a MK1 Zaffira) where the outfit was actually illegal then you have to question the way the advice works or is presented.

I don't think I have seen any publication from either of the clubs or the NCC that have misquoted the advice as having any greater authority, that issue seems to be caravanners and magazines. but the misquotes stick in peoples minds and so it is perpetuated.

There have been reports of some matching services who have marked certain combinations as good in what seems to be all areas but as soon as the ratio hits 85% it becomes a no no.

The lack of clarity about how the advice was formulated leaves me and others wondering how much thought if any went into its creation. For example its illogical to use criteria like kerbweight when such figures are sometimes not even published or are not specific to a particular model. Even some of my contacts within the industry confidentially admit the advice is actually hurting caravans sales.

One of my objectives in this is to encourage people to stop and think about this weight ratio tradition. If after proper analysis of the tradition is shown to be the best way then fine, but all too often traditions become outdated and its time this one was properly reviewed and evaluated to see if its fit for purpose.