My car weighs 1666kg. My 85% limit is therefore 1416kg. If I increase the car weight with luggage and a passenger can I increase the 85% figure accordingly provided I stay within the car towing limit and the caravan MTPLM?
85% Rule
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Damian
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- Mar 14, 2005
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First of all the 85% Rule is NOT a Rule, it is an advisory figure plucked out of the air over 20 years ago. It has NO legal standing.
Weight distribution is regulated by the car axle weights, and overall weight limit, plus the caravan weight limit and the overall rig weight limit , which depending on when you passed your car test can be 3500Kg overall.
I am sure that the topic must have been covered at length somewhere on the forum, use the search facility and see .
Other than that I am sure you will be inundated with very technical replies.
Weight distribution is regulated by the car axle weights, and overall weight limit, plus the caravan weight limit and the overall rig weight limit , which depending on when you passed your car test can be 3500Kg overall.
I am sure that the topic must have been covered at length somewhere on the forum, use the search facility and see .
Other than that I am sure you will be inundated with very technical replies.
While I agree it's not a rule, it's just an advisory figure - it wasn't just "plucked out of the air" - it's the combined experience over many decades by the Caravan Club who have published an advisory figue since just after WW2 - the % has varied mainly to reflect the different ways of measuring a car's weight.Damian-Moderator said:
If you've never towed before, 85% is a good place to start - then make your own mind up later when you have some experience.
The actual question was whether the % is applied to a higher car weight just because you load it up - and the answer is NO - so your 85% stays at 1416kg - if you want to tow a heavier caravan you'd have to accept that you're doing it at a higher %.
Thanks for that RogerL. I will just carry a smaller payload to keep my percentage as low as possible. Thanks Damian Moderator for the reminder on the legality of the "rule", but as I am very new to caravanning, I will endeavour to keep my van weight as low as possible to maximise stability.
Parksy
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- Nov 12, 2009
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Hi
It's desirable to keep the caravan weight low in relation to the towing vehicle but try to load so that the nose weight (Click Here to read about noseweight) is as close to your legal maximum limit as possible. Click Here for tips on loading your caravan correctly.
If there's anything that you're not sure about just ask
It's desirable to keep the caravan weight low in relation to the towing vehicle but try to load so that the nose weight (Click Here to read about noseweight) is as close to your legal maximum limit as possible. Click Here for tips on loading your caravan correctly.
If there's anything that you're not sure about just ask
- May 7, 2012
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If I remember rightly the 85% figure was arrived after the CC sponsored work by Bath University. It was a long time ago and designs have improved since then but I would suggest it is a good start for newcomers although 90% is reasonable for the more experienced and given a good combination this can be exceeded a bit..
- Mar 14, 2005
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Hello Ray,
Let me say from the outset, I think some advice is a useful thing for caravanners old and new, but it should really be practical and realistic. If after some proper research the evidence points to a notional figure then fine, but until that research is carried out then 85% is better than nothing, but I prefer to suggest keeping the caravan weight a small as possible compared to the tow vehicle.
As you well know the I see the issue of towing ratios is a bit of a hot potato. I am not happy with setting a fixed value, as it fails to offer any guarantees.
For many years the industry advice has quoted 85%, and it has become a mantra for many, yet it over emphasis the weight ratio when in practice it is one of several very important factors that contribute to the safety of towing.
Despite extensive searches I have made I have not been able to find any evidence of any scientific investigation to verify how the advice was derived. Non of the organisations who apparently would have been party to the decision making process will disclose or confirm the process used to derive this advice.
The University of Bath University (not Bath University). have been involved with certain specific studies, and it is interesting that one abstract suggests all is not well with the industries advice:-,
http://pid.sagepub.com/content/223/4/471
Abstract
Previous work on car—trailer stability has been largely limited to theoretical studies with some reference to practical experience or accident statistics. In this study, extensive and systematic experimental investigations were carried out on a combined car—adjustable-trailer system. The influence of different trailer parameters on the system high-speed stability was examined by changing the mass, dimensions, and inertial characteristics of a fully adjustable trailer. It was found that the dominant factors affecting stability were the trailer yaw inertia, nose mass (mass distribution), and trailer axle position. The tyre pressure also affects the stability, although this effect is less significant. It is interesting to see that the trailer mass alone does not dramatically affect the high-speed stability, as this runs contrary to current guidelines relating to limits on the relative mass of the car and trailer. Experimental tests on a friction stabilizer and on car electronic stability programs demonstrate that both of these improve the high-speed stability and help to delay the onset of ‘snaking’.
I have highlighted the section that seems to call into question the basis of the industries advice.
If you have some new information I would be very interested to follow it up.
Let me say from the outset, I think some advice is a useful thing for caravanners old and new, but it should really be practical and realistic. If after some proper research the evidence points to a notional figure then fine, but until that research is carried out then 85% is better than nothing, but I prefer to suggest keeping the caravan weight a small as possible compared to the tow vehicle.
As you well know the I see the issue of towing ratios is a bit of a hot potato. I am not happy with setting a fixed value, as it fails to offer any guarantees.
For many years the industry advice has quoted 85%, and it has become a mantra for many, yet it over emphasis the weight ratio when in practice it is one of several very important factors that contribute to the safety of towing.
Despite extensive searches I have made I have not been able to find any evidence of any scientific investigation to verify how the advice was derived. Non of the organisations who apparently would have been party to the decision making process will disclose or confirm the process used to derive this advice.
The University of Bath University (not Bath University). have been involved with certain specific studies, and it is interesting that one abstract suggests all is not well with the industries advice:-,
http://pid.sagepub.com/content/223/4/471
Abstract
Previous work on car—trailer stability has been largely limited to theoretical studies with some reference to practical experience or accident statistics. In this study, extensive and systematic experimental investigations were carried out on a combined car—adjustable-trailer system. The influence of different trailer parameters on the system high-speed stability was examined by changing the mass, dimensions, and inertial characteristics of a fully adjustable trailer. It was found that the dominant factors affecting stability were the trailer yaw inertia, nose mass (mass distribution), and trailer axle position. The tyre pressure also affects the stability, although this effect is less significant. It is interesting to see that the trailer mass alone does not dramatically affect the high-speed stability, as this runs contrary to current guidelines relating to limits on the relative mass of the car and trailer. Experimental tests on a friction stabilizer and on car electronic stability programs demonstrate that both of these improve the high-speed stability and help to delay the onset of ‘snaking’.
I have highlighted the section that seems to call into question the basis of the industries advice.
If you have some new information I would be very interested to follow it up.
- Jun 20, 2005
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John
I have no wish to be pedantic but the correct phrase is University of Bath.
As a post graduate of the University of Life as indeed are many others on here
I suggest we are all living examples of well seasoned caravanner.
85% ratio is I agree somewhat notional.As us old lags know it is one of many factors that contribute to a" safer tow".
SWMBO did a CC towing course 10 years ago. Two days hand's on. The detailed information even taught me a lot!
For a newbie I suggest they attend one of the club's courses.
Bailey still support research at University of Bath.
Have you noticed how the draw bar and hitch to axle lengths have gradually increased over the years.
I believe an 85% ratio for a newbie is wise providing all the other important loading factors are taken into account.
I have no wish to be pedantic but the correct phrase is University of Bath.
As a post graduate of the University of Life as indeed are many others on here
I suggest we are all living examples of well seasoned caravanner.
85% ratio is I agree somewhat notional.As us old lags know it is one of many factors that contribute to a" safer tow".
SWMBO did a CC towing course 10 years ago. Two days hand's on. The detailed information even taught me a lot!
For a newbie I suggest they attend one of the club's courses.
Bailey still support research at University of Bath.
Have you noticed how the draw bar and hitch to axle lengths have gradually increased over the years.
I believe an 85% ratio for a newbie is wise providing all the other important loading factors are taken into account.
bit of a European me, i wonder have any of our seasoned travellers abroad ever come across an advisor towing weight abroad in Holland France Germany Italy? ect ect.. also the" 85% rule" as stated elsewhere is somewhat of an old saying? and with modern caravan going back to proper suspension and indeed following the Europeans with longer draw bars, i wonder how relevant that research [85% rule] is today..
Have a look at the German Tempo 100 rules below - the requirements to tow a 100% caravan at 62 mph are very strict - there is an easier level which allows an 80% caravan to be towed at 62 mph - for those not metting the requirements, it's restricted to 50 mph.
There is no equivalent level of registration AND technical standards in the UK that's equivalent to Germany's 100% at 62 mph - the next level of 80% is roughly equivalent to ours - and the blanket level is slower than the UK - so quit banging on about foreign tuggers!
"Generally, a speed limit of 80 km/h, or Tempo 80, applies for trailers. Those who wish to drive faster can now have their vehicle and trailer assessed for suitability at any TÜV STATION. On successful completion of the assessment, you receive a confirmation which you can take to your local vehicle registration authority in order to receive a Tempo 100 sticker. Vehicles and trailers have to fulfil the following criteria:
Your car must be equipped with ABS
The maximum permissible laden weight of your car is 3,500 kg
The trailer is suitable for a maximum speed of 100 km/h
The trailer tyres are designed for Tempo 120 and have at least speed index L
The tyres are no more than six years old
You have to comply with specific weight proportions between the trailer and the towing vehicle
Load the trailer in such a way that the maximum permissible towbar load of the combination is almost reached. Make sure that you do not exceed the permissible towbar load of the towing vehicle or that of the trailer. Reason: You significantly improve the manageability of your combination with a high towbar load.
Watch your weight
The permissible laden weight of the trailer may not exceed any of the following three values:
The total towing capacity of the towing vehicle
The permissible laden weight of the towing vehicle
The product of X • unladen weight of the towing vehicle
Factor X consists of one the following values, depending on the technical equipment of the vehicle:
technical equipment of the trailer
without hydraulic shock absorbers with brakes and hydraulic shock absorbers
Caravan Other trailers
0,3 0,8 or 1,0* 1,1 or 1,2*
The values marked with "*" (asterisk) may be used if:
the trailer is equipped with a suitable coupling with stabilising device or
the trailer is equipped with a suitable dynamic stability system or
the towing vehicle is equipped with a suitable dynamic stability system for towing (this is stated in the vehicle registration document)."
There is no equivalent level of registration AND technical standards in the UK that's equivalent to Germany's 100% at 62 mph - the next level of 80% is roughly equivalent to ours - and the blanket level is slower than the UK - so quit banging on about foreign tuggers!
"Generally, a speed limit of 80 km/h, or Tempo 80, applies for trailers. Those who wish to drive faster can now have their vehicle and trailer assessed for suitability at any TÜV STATION. On successful completion of the assessment, you receive a confirmation which you can take to your local vehicle registration authority in order to receive a Tempo 100 sticker. Vehicles and trailers have to fulfil the following criteria:
Your car must be equipped with ABS
The maximum permissible laden weight of your car is 3,500 kg
The trailer is suitable for a maximum speed of 100 km/h
The trailer tyres are designed for Tempo 120 and have at least speed index L
The tyres are no more than six years old
You have to comply with specific weight proportions between the trailer and the towing vehicle
Load the trailer in such a way that the maximum permissible towbar load of the combination is almost reached. Make sure that you do not exceed the permissible towbar load of the towing vehicle or that of the trailer. Reason: You significantly improve the manageability of your combination with a high towbar load.
Watch your weight
The permissible laden weight of the trailer may not exceed any of the following three values:
The total towing capacity of the towing vehicle
The permissible laden weight of the towing vehicle
The product of X • unladen weight of the towing vehicle
Factor X consists of one the following values, depending on the technical equipment of the vehicle:
technical equipment of the trailer
without hydraulic shock absorbers with brakes and hydraulic shock absorbers
Caravan Other trailers
0,3 0,8 or 1,0* 1,1 or 1,2*
The values marked with "*" (asterisk) may be used if:
the trailer is equipped with a suitable coupling with stabilising device or
the trailer is equipped with a suitable dynamic stability system or
the towing vehicle is equipped with a suitable dynamic stability system for towing (this is stated in the vehicle registration document)."
- May 7, 2012
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It is very difficult to judge the stability of an outfit before purchase so as I see it watching the weight ratio is the best you can do. Stability relies on a lot more than just vehicle weights and watching loading, nose weights and so on are equally important. Both clubs do their best with advice but probably dealers need to do more giving advice or a decent booklet on the subject but as far as I can see many just want to shift stock and ask no questions on experience tow cars or anything else.
hi all,
Personally Ray, I wish the dogma of the 85% (rule) recommendation was finally put to rest, it is has about as much relevance to modern caravanning as the red flag has to modern motoring in general, yet is one of the first points picked up and given to newbie caravanners. despite the realms of legistlation brought in over the years and the importance of correct loading and driving techniques. the obsession with weight ratios is scull numbing.
it would not be so bad IF the organisations that recommend it could explain why after 40+ years they still stick with it when the criteria for making the rule "sorry" recommendation died out decades ago along with steam engines and cobbled streets !!!.
back then it may have been prudent to fix some sort of guidance for joe public wishing to tow a 16ft sprite with a moggy 1000. on A and B roads,down to cornwall (if the engine made it that far) even though most outfits at the time would have complied anyway,
back then cars were heavier and caravans lighter, most cars had drum brakes. no ABS or power steering tow bars were attached by drilling and bolting though the body work (body pull type) that had limited towing capacity and the average 2.0 litre engine had less power than a small modern diesel.
A time when there was no or very few motorways no ABS, traction control, ATC's or stabiliser hitches, a bygone age left squarely in history.
so why then has this recommendation stood the test of time, well because no one has come up with anything that fits this modern age, doing the research testing and compiling the results costs money and no one is prepared to pay for it.
it is far easier to quote outdated theory and pass it off as relevent without having to explain why!!
a far better way would be to recommend that the trailer load is as small as is practical for a given tow car irrespective of the actual weight, with the emphasis placed on the true towing capacity of the vehicle in question having due regards for the legal requirements in place by legistlation.
Personally Ray, I wish the dogma of the 85% (rule) recommendation was finally put to rest, it is has about as much relevance to modern caravanning as the red flag has to modern motoring in general, yet is one of the first points picked up and given to newbie caravanners. despite the realms of legistlation brought in over the years and the importance of correct loading and driving techniques. the obsession with weight ratios is scull numbing.
it would not be so bad IF the organisations that recommend it could explain why after 40+ years they still stick with it when the criteria for making the rule "sorry" recommendation died out decades ago along with steam engines and cobbled streets !!!.
back then it may have been prudent to fix some sort of guidance for joe public wishing to tow a 16ft sprite with a moggy 1000. on A and B roads,down to cornwall (if the engine made it that far) even though most outfits at the time would have complied anyway,
back then cars were heavier and caravans lighter, most cars had drum brakes. no ABS or power steering tow bars were attached by drilling and bolting though the body work (body pull type) that had limited towing capacity and the average 2.0 litre engine had less power than a small modern diesel.
A time when there was no or very few motorways no ABS, traction control, ATC's or stabiliser hitches, a bygone age left squarely in history.
so why then has this recommendation stood the test of time, well because no one has come up with anything that fits this modern age, doing the research testing and compiling the results costs money and no one is prepared to pay for it.
it is far easier to quote outdated theory and pass it off as relevent without having to explain why!!
a far better way would be to recommend that the trailer load is as small as is practical for a given tow car irrespective of the actual weight, with the emphasis placed on the true towing capacity of the vehicle in question having due regards for the legal requirements in place by legistlation.
There has to be simple advice for newbies - think of the basic question they ask - "I've got car xyz, what caravan can I tow safely ?"
Understanding any Towing Ratio is hard enough for a newbie - more complex advice isbeyond them, at that stage.
"Small as practical" gives a newbie no help at all - it's not wrong, just unhelpful.
Understanding any Towing Ratio is hard enough for a newbie - more complex advice isbeyond them, at that stage.
"Small as practical" gives a newbie no help at all - it's not wrong, just unhelpful.
Ok Roger, want it simple :blink: question ? " "I've got car xyz, what caravan can I tow safely ?"
1. answer = what does it say on the V5 document under max trailer weight ??? well that is the maximum so it has to be less than that,
2. if there is no weight on the V5 document, "vehicles registered before 2005" look at the Vin plate the two largest figures are Gross vehicle weight (smallest) and gross train weight (largest) deduct the smallest from the largest the figure left is the maximum trailer weight, it has to be lower than this.
(please note) these are the maximum weights allowed, a new caravanner would be advised not to tow at these weights to begin with but choose a van that is considerably less than the maximum, in fact the lighter the better,
how that!!.
edit.
the assumption that newbies are somehow stupid and cannot handle anything but the simplist of calculations or advice in my view is wrong, hell the real test is getting to grips with all the legistlation in place. if they cannot handle the basic premiss of lighter is better there would be no hope for them later on!!!!!!!!.
1. answer = what does it say on the V5 document under max trailer weight ??? well that is the maximum so it has to be less than that,
2. if there is no weight on the V5 document, "vehicles registered before 2005" look at the Vin plate the two largest figures are Gross vehicle weight (smallest) and gross train weight (largest) deduct the smallest from the largest the figure left is the maximum trailer weight, it has to be lower than this.
(please note) these are the maximum weights allowed, a new caravanner would be advised not to tow at these weights to begin with but choose a van that is considerably less than the maximum, in fact the lighter the better,
how that!!.
edit.
the assumption that newbies are somehow stupid and cannot handle anything but the simplist of calculations or advice in my view is wrong, hell the real test is getting to grips with all the legistlation in place. if they cannot handle the basic premiss of lighter is better there would be no hope for them later on!!!!!!!!.
It covers some of the legalities but none of the practicalities - quite a number of towcars have towing limit way in excess of 100% of kerbweight, quite useful for experienced tuggers and low CoG trailers - but useless for caravanners, experienced or newbies.colin-yorkshire said:
what about themWoodlandsCamper said:
85% is no guarantee the outfit would be under the 3500kg limit for a cat B licence.colin-yorkshire said:
There is another thread running about someone lifting their van on the steadies rather than lifting the wheel. What was that about newbies not being stupid??
RogerL said:
whats kerb weight!!! surely you mean "mass in service" or MAM. the vehicles you speak of are at the top end of the tuggers list, a caravan that weighs the upper limits ,of these vehicles would not be contemplated by a newbie or should not be, remember the "as light as possible bit"
who said he was a newbie could have been doing this for years :woohoo:WoodlandsCamper said:colin-yorkshire said:
There is another thread running about someone lifting their van on the steadies rather than lifting the wheel. What was that about newbies not being stupid??
Mel
Moderator
- Mar 17, 2007
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When I was new to caravanning there seemed to be such a lot to understand that I didn't care what was backed up by science and what wasn't. What I wanted was some straightforward, easy to act on, advice. I was glad that there was a 85% rule/guideline/myth as it mean't that I had somewhere to start. Some years in I was in a far better position to weigh up the debate around it.
Newbies are not necessarily stupid (although some may be more stupid than others; to misquote Orwell) but are often overwhelmed by information. This may be to the extent that they give up on the idea of Caravanning. This would be BAD.
mel
Newbies are not necessarily stupid (although some may be more stupid than others; to misquote Orwell) but are often overwhelmed by information. This may be to the extent that they give up on the idea of Caravanning. This would be BAD.
mel
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