In this week's blog, our tow car expert David Motton debates the pros and cons of the 85% rule. Read his thoughts by clicking here. What do you think? Let us know.
What do you think of the 85% rule?
- Thread starter LizziePope
- Start date
With the new car the ratio is 75% but haven't towed with it yet. The car has stability control including trailer, but the van only has an AL-KO stabilised hitch. On paper I should have a stable outfit but proof will be when I get the outfit on the road next spring.
LizziePope said:
Hello Lizzie,
I'm more than highly disappointed to see both David Motton and yourself perpetuated the very misleading use of the word “rule” in a headline in connection with the caravan industry 85% and 100% towing ratios. Notwithstanding the clarification David later gives in the article confirming the guidance, not a rule, it’s the headline that will be most remembered. Practical Caravan Magazine is a respected publication that should be a vanguard of supporting good practice and providing high quality non sensationalised information. Tabloid style misleading headlines should be avoided.
I could forgive it if it were quoted as a “Rule of thumb” which implies it's a methodology rather than a precise specification, but just using the word “Rule” means it is easily misconstrued as having some legal or safety significance.
this topic comes up from time to time and it never ceases to amaze me why some think a magical figure of 85% is going to make a unit either stable or easier to handle than any other figure one could pluck out of thin air.
a few years ago there was a long debate about this, so in the interests of fairness I did quite a lot of research on the subject, the more one delved into the why's and wherefore's the more it got confusing, because it is not a universal "rule" [sorry John] while it may be true that both the major clubs and the ncc all sort of recommend it, the origins of the "recommendation" are quite obscure and there is not a universal way of calculating it.
if one reads the the detail of the recommendation, it seems some vital gaps in the information are missing, which has the effect that each organisation that recommends it does it slightly differently, but because the average user takes what is said as gospel, it then becomes gospel and other bodies like the PC magazine also recommend it, which is a shame because it can make newbies and some die hard veterans reject either a perfectly good caravan or tow car simply because it does not conform to the now established "rule" of 85% thinking 86% is bad and 84% is good when in effect anything between 80 and 100% would be fine. proving the user paid attention to correct loading and driving style but none of this is mentioned along with the recommendation. it is put across as a magic solution to stable towing and of course it is not.
if you remember the fact that the 85% was devised decades ago when the caravan weights increased due to more equipment and at the same time tow car weights decreased due to the sudden increase in fuel costs, plus there wasn't any meaningful legislation attached to towing, you may see where the idea came from, but even then it did not add up.
using the unladen weight of the tow car, against the MTPLM of the van, may give an interpretation of the worst case scenario, but as soon as the tow car was loaded and the "van" loaded for towing the 85% ratio disappeared completely, so really had no relevance to the true towing ratio, is was for this very reason the difference between the recommendations of organising bodies differed slightly,
now of course we have reams of legislation covering towing, that would in effect make any recommendation meaningless, so to answer David's question is the "rule" relevant today absolutely not, the basis for it's use has long since gone, together with the cars and vans it was intended for.
now we use the weight plates to do the calculations as the tow car manufactures take great steps to insure their cars are up to the job and state the correct maximum trailer weight one can tow, this is no longer a "rule" or recommendation but the law,
if one just had to recommend something for the newbies to follow it would be better to recommend that the total trailer weight is kept as small as practically possible, with the main aspects aimed at correct loading and driving style,
a few years ago there was a long debate about this, so in the interests of fairness I did quite a lot of research on the subject, the more one delved into the why's and wherefore's the more it got confusing, because it is not a universal "rule" [sorry John] while it may be true that both the major clubs and the ncc all sort of recommend it, the origins of the "recommendation" are quite obscure and there is not a universal way of calculating it.
if one reads the the detail of the recommendation, it seems some vital gaps in the information are missing, which has the effect that each organisation that recommends it does it slightly differently, but because the average user takes what is said as gospel, it then becomes gospel and other bodies like the PC magazine also recommend it, which is a shame because it can make newbies and some die hard veterans reject either a perfectly good caravan or tow car simply because it does not conform to the now established "rule" of 85% thinking 86% is bad and 84% is good when in effect anything between 80 and 100% would be fine. proving the user paid attention to correct loading and driving style but none of this is mentioned along with the recommendation. it is put across as a magic solution to stable towing and of course it is not.
if you remember the fact that the 85% was devised decades ago when the caravan weights increased due to more equipment and at the same time tow car weights decreased due to the sudden increase in fuel costs, plus there wasn't any meaningful legislation attached to towing, you may see where the idea came from, but even then it did not add up.
using the unladen weight of the tow car, against the MTPLM of the van, may give an interpretation of the worst case scenario, but as soon as the tow car was loaded and the "van" loaded for towing the 85% ratio disappeared completely, so really had no relevance to the true towing ratio, is was for this very reason the difference between the recommendations of organising bodies differed slightly,
now of course we have reams of legislation covering towing, that would in effect make any recommendation meaningless, so to answer David's question is the "rule" relevant today absolutely not, the basis for it's use has long since gone, together with the cars and vans it was intended for.
now we use the weight plates to do the calculations as the tow car manufactures take great steps to insure their cars are up to the job and state the correct maximum trailer weight one can tow, this is no longer a "rule" or recommendation but the law,
if one just had to recommend something for the newbies to follow it would be better to recommend that the total trailer weight is kept as small as practically possible, with the main aspects aimed at correct loading and driving style,
To some extent I agree with Colin but what is clear is that the heavier the car is in comparison with the caravan the safer the combination should be. There is no safe level for all combinations it must vary according to the differing towing ability of each model of car and caravan. The problem then is you have to advise newcomers to towing what to avoid for safety reasons and the 85% figure is the best we have for those inexperienced. The advice is that this is essentially this is for newcomers and once you have built up experience you can exceed this but opinions vary as to how far you can go but exceeding the cars kerb weight is generally not recommended by any of the groups advising.
Coming from a background involving accident investigation, but not having been involved in any detailed investigation into the problem as a whole, I can only say I have only ever seen the roll over problem where the caravan has been very near or over the kerb weight of the car and certainly well over the 85% figure.
From a drivers point of view you will never know if your outfit is safe unless you get into a situation where it becomes clear it is not and then it is far too late so I have to advise that you should err on the side of caution. It is too late to find out you got it wrong when the caravan is in bits at the side of the road.
Personally I have always tied to keep the ratio at no more than 90% and currently tow at 86%.
Coming from a background involving accident investigation, but not having been involved in any detailed investigation into the problem as a whole, I can only say I have only ever seen the roll over problem where the caravan has been very near or over the kerb weight of the car and certainly well over the 85% figure.
From a drivers point of view you will never know if your outfit is safe unless you get into a situation where it becomes clear it is not and then it is far too late so I have to advise that you should err on the side of caution. It is too late to find out you got it wrong when the caravan is in bits at the side of the road.
Personally I have always tied to keep the ratio at no more than 90% and currently tow at 86%.
When I started caravanning 5 years ago, I became aware of the recommendation/rule of 85% and took it on board when looking for a tow car. I ended up at 87% and thought this would be OK, as it was near enough, so inavertantly fell in with most experienced caravanners view of the situation.
When returning from a trip to France a few years back, I witnessed what most people have never seen, when the Bailey Twin Axle in front of me jumped at least a metre to the left, them back 2 metres to the right a couple of times. Fortunately the driver was able to hold it together and get to the hard shoulder, as I passed I looked at the towing vehicle, and I think it was a Mitsubishi Shogun and would have been within 85%. I do not think the van had ATS as it was a few years old, and as we followed it for at least 45 miles, we had noticed the van was moving about, despite the driver driving in a good manner. It really made me agree with the 85% recommendation/rule, call it whatever you want, particularly for new towers.
As an aside to this we had intended to buy our van at a local dealership and when on a visit we spoke to the salesman we intended to buy it from. He asked us where we where on making a decision to buy, I said that we had decided on the van we wanted, but had to sort out a towing vehicle. He asked what car we had and when we told him he said that it was OK as the recommendation/rule was a load of B..........ks. He lost the sale at that moment, as the car was lower in weight than the van we intended to purchase.
Does it matter where the recommendation/rule came from, it just makes sense that the vehicle should be heavier than the van in cas you have a problem like the Bailey driver.
When returning from a trip to France a few years back, I witnessed what most people have never seen, when the Bailey Twin Axle in front of me jumped at least a metre to the left, them back 2 metres to the right a couple of times. Fortunately the driver was able to hold it together and get to the hard shoulder, as I passed I looked at the towing vehicle, and I think it was a Mitsubishi Shogun and would have been within 85%. I do not think the van had ATS as it was a few years old, and as we followed it for at least 45 miles, we had noticed the van was moving about, despite the driver driving in a good manner. It really made me agree with the 85% recommendation/rule, call it whatever you want, particularly for new towers.
As an aside to this we had intended to buy our van at a local dealership and when on a visit we spoke to the salesman we intended to buy it from. He asked us where we where on making a decision to buy, I said that we had decided on the van we wanted, but had to sort out a towing vehicle. He asked what car we had and when we told him he said that it was OK as the recommendation/rule was a load of B..........ks. He lost the sale at that moment, as the car was lower in weight than the van we intended to purchase.
Does it matter where the recommendation/rule came from, it just makes sense that the vehicle should be heavier than the van in cas you have a problem like the Bailey driver.
While i understand that the 85% is the ideal.
On my vehicle at the kerb weight at 85% I could tow 1530 approx.
Fully laden this increases to 1870 approx.
Both of these figures fall well short of the official maximum towing ability of 2100kg for my vehicle.
I have been refused a caravan that weighed more than the kerb weight on the grounds of it would invalidate my insurance.
So where do we go from here, officially my vehicle is capable of safely towing at 130% +, my previous vehicle could tow a maximum of 1200kg and I towed a van at this weight without any difficulties in all weather conditions.
Even the towcar awards list the maximum manufactures towing capacity for their vehicles.
So where do we go from here?
On my vehicle at the kerb weight at 85% I could tow 1530 approx.
Fully laden this increases to 1870 approx.
Both of these figures fall well short of the official maximum towing ability of 2100kg for my vehicle.
I have been refused a caravan that weighed more than the kerb weight on the grounds of it would invalidate my insurance.
So where do we go from here, officially my vehicle is capable of safely towing at 130% +, my previous vehicle could tow a maximum of 1200kg and I towed a van at this weight without any difficulties in all weather conditions.
Even the towcar awards list the maximum manufactures towing capacity for their vehicles.
So where do we go from here?
intransient1 said:
You must remember that trailers come in all shapes and sizes, from 'big and boxy' to 'low and heavy'. A flat bed trailer with a tonne or so of sand on it, or indeed another car, has a very low centre of gravity and could weigh over 2 tonnes so would be relatively stable in windy conditions. In contrast a caravan is not the ideal shape due to its sail effect and will be very susceptible to rapid changes in cross winds, created by overtaking vehicles, gaps in hedges or building, bridges, etc. and therefore more likely to exert unwanted forces on the towing vehicle. The lower the ratio between caravan and car will therefore allow the towing vehicle to be in better control of the outfit.
So your vehicle comes in at 1800kgs?intransient1 said:
the official maximum towing ability of 2100kg for my vehicle.
As you probably know this has nothing to do with a safe load imo. It basically means the vehicle can do a standing start on a steep hill with this load.
Rather than repeat the volumes Colin and The Prof have written finitely explaining this subject maybe the search engines can point you to the advice given . It's a shame this forum doesn't have a "library" section where all the pearls of wisdom could be stored for easy reference.
Many years ago I towed at over 100% ratioas the usual tug was in the garage. No problem with power but when it came to an emergency stop there were bricks on my seat :woohoo: The caravan was pushing hard even though the brakes were functioning.
with a heavy 4x4 I've never felt the tail wag the dog. Ok it is not everyones choice and there is a cost element but these days I prefer to take it easy and not push the boundaries to their limit.
Have to agree with the Prof. it's a guide not a rule and even then needs some study and understanding. Kerb weight is not defined in any standard way - some makes include driver and some don't etc. and there is train weight to consider as well.
I think it has a place for the beginner and as a very coarse screen when considering a change of towcar or caravan, but has less to do with stability than intelligent weight distribution, correct tyre pressures, hitch height etc.
I think it has a place for the beginner and as a very coarse screen when considering a change of towcar or caravan, but has less to do with stability than intelligent weight distribution, correct tyre pressures, hitch height etc.
As an all year round towing caravanner , i prefer and I am financially capable to have heavier car, if your moving to and from a seasonal pitch then if carefull towing at maybe a higher limit should be ok, BUT, becareful not to overload your van and car , it so east to overload tour car and van with a full size awning the Bbq, awning matting, exrta fridge, etc, you can soon get over your Mass tow weight .
Hutch
Hutch
d
Dusty Dog, I have never experienced a "Tail Wagging the Dog", towed past trucks at 65 mph +( Only in France!!!) To get past the slower moving trucks, but earlier This year, at about 62 mph.
( i know Over the limit), got in ro a real, tail shake. Had i been a cat i would have buried it. Thankfully the AlKo trailer kit kicked in. Checked all my balance and nose weights, the only thing I found wrong was my friction pads on the ALKO tow hitch. And my want to get past an articulated truck. , IT 'S NOT WORTH IT...
Dusty Dog, I have never experienced a "Tail Wagging the Dog", towed past trucks at 65 mph +( Only in France!!!) To get past the slower moving trucks, but earlier This year, at about 62 mph.
( i know Over the limit), got in ro a real, tail shake. Had i been a cat i would have buried it. Thankfully the AlKo trailer kit kicked in. Checked all my balance and nose weights, the only thing I found wrong was my friction pads on the ALKO tow hitch. And my want to get past an articulated truck. , IT 'S NOT WORTH IT...
I suppose if nothing else this topic is really getting some of the misconceptions out into the air.
The tail wagging the dog, has been used again.
The concept of this is if the trailer is heavier than the tow vehicle it can start to control the outfits behavior. Well yes it can, BUT the effect can also occur when the trailer is lighter than the tow vehicle hmy: Its principally down to how the outfit is loaded and driven.
"Kerbweight"
A fanciful figure which has so many definitions its barely worth the paper its printed on - if you can even find it..
85% & 100% ratios
Notional figures plucked out of the air (it seems) which in fact bear no relationship to the actual weight ratio of the trailer compared to the tow vehicle when towing, They take no account of the tow vehicles specification - as some are not even permitted to pull an 85% trailer. There is no sudden change in the handling of an outfit simply because you exceed either of these figures. Yet despite their inconsistences and no legal relevance they are seen as the holy grail by so many. . :dry:
Its amazing these totally unscientific figures with no legal impact and of uncertain origin, are seen and so zealously misquoted as a "rule" such they has become a mantra, and a holy grail.
Its so amazing that so much effort goes into meeting these non entities, yet such casual regard is given to other matters that have legal implications such as
Speed limits
Nose load
Using a mobile phone whist driving
Seat Belts
Stopping at stop line at junctions
under taking
Lane discipline
Tail gating
Parking on ZigZags out side schools and crossings
misuse of Blue badges and disabled parking spaces
Wearing baseball hats the wrong way round,and listening to music at volumes you can hear half a mile away, smoking (probably a splif)
Lets gets some proper logical perspective on these matters.
The tail wagging the dog, has been used again.
The concept of this is if the trailer is heavier than the tow vehicle it can start to control the outfits behavior. Well yes it can, BUT the effect can also occur when the trailer is lighter than the tow vehicle hmy: Its principally down to how the outfit is loaded and driven. "Kerbweight"
A fanciful figure which has so many definitions its barely worth the paper its printed on - if you can even find it..
85% & 100% ratios
Notional figures plucked out of the air (it seems) which in fact bear no relationship to the actual weight ratio of the trailer compared to the tow vehicle when towing, They take no account of the tow vehicles specification - as some are not even permitted to pull an 85% trailer. There is no sudden change in the handling of an outfit simply because you exceed either of these figures. Yet despite their inconsistences and no legal relevance they are seen as the holy grail by so many. . :dry:
Its amazing these totally unscientific figures with no legal impact and of uncertain origin, are seen and so zealously misquoted as a "rule" such they has become a mantra, and a holy grail.
Its so amazing that so much effort goes into meeting these non entities, yet such casual regard is given to other matters that have legal implications such as
Speed limits
Nose load
Using a mobile phone whist driving
Seat Belts
Stopping at stop line at junctions
under taking
Lane discipline
Tail gating
Parking on ZigZags out side schools and crossings
misuse of Blue badges and disabled parking spaces
Wearing baseball hats the wrong way round,and listening to music at volumes you can hear half a mile away, smoking (probably a splif)
Lets gets some proper logical perspective on these matters.
intransient1 said:
Hello Intransient,
What makes 85%the ideal? Is there any scientific proof that is the correct figure? Realistically it may be a good figure for a few outfits but not all.
Conventionally the towing ratio is always quoted on the trailer MTPLM vs the tow vehicles kerbweight., and the figure does not move when you load the vehicles.
The sales person who told you could not tow anything that exceeded the cars kerbweight was wrong. Unless of course the particular vehicle in question had a towed weight limit that was less than the cars kerbweight. However your insurance policy is based on the car manufacturer's specification, and it will cover you provided you are licenced to drive the outfit (Cat B only 1997 to 2013 does limit trailers to less than the unladen weight [not kerbweight] of the vehicle] and you do not exceed the tow vehicles specifications.
Dustydog said:
Sorry Dusty,
But the overrun brakes on caravans only rely on the tow vehicle being heavy enough to be able to resist the compression of the tow hitch and to activate the brakes on the caravan. This should not exceed a couple of hundred pounds thrust. If that was upsetting the tow car then it points to the fact the caravan brakes were not functioning properly.
If however the braking was sufficient set both the trailer and the tow car into a skid ( Wheels not rotating) then yes the bigger the trailer the more serious the skid will be.
When i read threads like this,it always amazes me when i hear these horror stories such as tail wagging dog and outfits jumping across the carrige way and whilst for one minute i dont doubt it,i wonder how and what causes it?Ive towed for almost 12 years,always had high powered diesels,and admit ive not been a saint when we,ve been late for a ferry,but in that time ive never had so much as a sniff.There must be more to it than stated.
Tail wagging the dog is this old dogs reference to a snake or whatever animal you choose.It is of no significant technical relevance.
For the sake of clarity the emergency stop was years ago with a Castleton Rovanna tugged by an old Triumph Vitesse. Not a good combination but those were in the days when money was tight and perhaps there was more of a gungho attitude
So come on Lizzie how about PCv doing a comprehensive paper on the whole subject.As I said earlier the Prof and Colin have written volumes on here.
For the sake of clarity the emergency stop was years ago with a Castleton Rovanna tugged by an old Triumph Vitesse. Not a good combination but those were in the days when money was tight and perhaps there was more of a gungho attitude
So come on Lizzie how about PCv doing a comprehensive paper on the whole subject.As I said earlier the Prof and Colin have written volumes on here.
This is a bit long winded but shows the dynamics involved when passing or being passed by a lorry,
http://caravanchronicles.com/guides/understanding-the-dynamics-of-towing-being-overtaken/
Hutch
http://caravanchronicles.com/guides/understanding-the-dynamics-of-towing-being-overtaken/
Hutch
The continual renewal of the advice to keep a caravan within the industries weight guidelines does have its place, but logically the single biggest element to affect the towing of a caravan is the driver. You can have the most unstable outfit in the world and it's fine when it's stationary, It only becomes a problem when it's being towed, and its the driver that causes it to be towed.
It may be manageable below a certain speed, but ignore the warning signals and continue to increase your speed and it become unmanageable. Who makes that decision - the driver.
I will continue to repeat the message that in law the driver is responsible for the condition and safety of the vehicle, so again it's the driver that should complete all the necessary checks before they start a journey and ensure the caravan and tow vehicle are load properly.
The Industry guidance is flawed. it does not any guarantee of safety or good towing characteristics, how can it? - it's based on unobtainable conditions that certainly do not represent the real towing ratio of the outfit. And the figures they apply have not been backed up with any scientific evidence. But then it was not claimed to offer safety or guarantees, it was alway guidance and never given any regulatory impact - it is only the continual mis quoting of the guidance that has generated this missguided perception of being the precipice which you must not breach.
The danger of this is whilst for some outfits 85% is very conservative, whereas for others 85% maybe too much, and again this is where the driver must apply good sense to check the specification and to manage the proper loading of car and caravan.
I criticise the specific use of the 85 and 100% figures, because they do not represent what they imply, and because without scientific evaluation, how can we have confidence the figures are fit for purpose? There should be no doubt that some traffic incidents involving caravan instability have occurred with outfits that did comply with the guidance, so that calls into question the figures given. I am of the opinion this understanding suggests the novice guidance should be reduced, but as I cannot undertake any comprehensive testing to establish the safe figure, I am unable to suggest a figure.
Guidance can be an important source of information for newcomers, but the guidance given should be robust and offer some provable levels of safety. Without doubt this is a highly contentious issue and realistically it should be part of a wider package of advice that also includes advice about loading, maintenance and driving habits.
It may be manageable below a certain speed, but ignore the warning signals and continue to increase your speed and it become unmanageable. Who makes that decision - the driver.
I will continue to repeat the message that in law the driver is responsible for the condition and safety of the vehicle, so again it's the driver that should complete all the necessary checks before they start a journey and ensure the caravan and tow vehicle are load properly.
The Industry guidance is flawed. it does not any guarantee of safety or good towing characteristics, how can it? - it's based on unobtainable conditions that certainly do not represent the real towing ratio of the outfit. And the figures they apply have not been backed up with any scientific evidence. But then it was not claimed to offer safety or guarantees, it was alway guidance and never given any regulatory impact - it is only the continual mis quoting of the guidance that has generated this missguided perception of being the precipice which you must not breach.
The danger of this is whilst for some outfits 85% is very conservative, whereas for others 85% maybe too much, and again this is where the driver must apply good sense to check the specification and to manage the proper loading of car and caravan.
I criticise the specific use of the 85 and 100% figures, because they do not represent what they imply, and because without scientific evaluation, how can we have confidence the figures are fit for purpose? There should be no doubt that some traffic incidents involving caravan instability have occurred with outfits that did comply with the guidance, so that calls into question the figures given. I am of the opinion this understanding suggests the novice guidance should be reduced, but as I cannot undertake any comprehensive testing to establish the safe figure, I am unable to suggest a figure.
Guidance can be an important source of information for newcomers, but the guidance given should be robust and offer some provable levels of safety. Without doubt this is a highly contentious issue and realistically it should be part of a wider package of advice that also includes advice about loading, maintenance and driving habits.
EH52ARH said:
Excellent drawings and it's nice to see the caravan's directional TV aerial is stowed pointing backwards, as it should be.
So how many cars are designed to tow a large 1-2 ton box?
Cars are designed as people carriers with a slight nod to a few quirky people who want to tow caravans.
By sticking a caravan on the back of a car the driver and passengers are exposing themselves to a whole host of extra risks and it is all about minimising those risks.
We all learn by experience and from guidance from experienced practitioners.
In the case of the 85% towing ratio .......this is guidance given by a whole host of experienced practitioners in caravanning.
You will always get people who question this guidance for various reasons and many will tell you they have ignored it for years without consequence.
These people are right in that the 85% guidance is not the law or the only factor to be taken into consideration.
I prefer to think of this guidance in a different way and think it should be.......... the towing vehicle's kerb weight should weigh 15% more than the caravan MTPLM.
I for one think this is a relevant and useful cut off figure to aim at.
The best advice is that the caravan should be as light as possible in relation to the towing vehicle.
With that in mind ........I tow at 62% ratio.
Cars are designed as people carriers with a slight nod to a few quirky people who want to tow caravans.
By sticking a caravan on the back of a car the driver and passengers are exposing themselves to a whole host of extra risks and it is all about minimising those risks.
We all learn by experience and from guidance from experienced practitioners.
In the case of the 85% towing ratio .......this is guidance given by a whole host of experienced practitioners in caravanning.
You will always get people who question this guidance for various reasons and many will tell you they have ignored it for years without consequence.
These people are right in that the 85% guidance is not the law or the only factor to be taken into consideration.
I prefer to think of this guidance in a different way and think it should be.......... the towing vehicle's kerb weight should weigh 15% more than the caravan MTPLM.
I for one think this is a relevant and useful cut off figure to aim at.
The best advice is that the caravan should be as light as possible in relation to the towing vehicle.
With that in mind ........I tow at 62% ratio.
That is a very good link,interesting how it refers to t/a caravans being more stable.Understandable really.
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