Tow weight ratios
Having re-checked something I thought I'd already checked, I found that my car (non-negotiable - won't be changed) that has a max tow weight of 1400kg would actually be at a 93% ratio on the "unladen car to fully laden caravan" scale.
I'm a bit confused as to the point of this ratio though - If its about stopping "the tail wagging the dog", then why not actually find the weight of the car on your actual journey and the weight of the caravan as you travel, and then compare those.
Our car for example is 1500kg unladen. But its not going to be unladen is it? Its going to have 200kg of people and about 100kg of stuff in it - making it 1800kg
The caravan I'm looking it is unladen 1175kg, and will have about 100kg of stuff in it (I only had about 150kg in my motorhome and I can't think of anything else I'd put in it on top of that - AND a lot of that stuff will now be in the car)
So the real world ratio is probably going to be under 1800/1275 = 71%. Surely that covers any tail-wagging??
What's got me thinking is that some vans have a far bigger payload than others depsite having similar unladen weights, and so this will penalise them on this 85% ratio, making them "a bad fit", when in the real world, they'd be exactly the same weight as another caravan that would tick the 85% ratio just fine.
Any views?
Comments
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Both major clubs recommend that for novice towers the relation between the cars kerb weight, including 75kg for the driver and the mtplm of the caravan should be 85%. For experienced towers this can be 100% but at no time should the mtplm of the van exceed the kerb weight of the car.
This is just a recommendation and not a law/requirement.
Kerb weight and mtplm are used as they are standard figures quoted by all car and caravan manufacturers. Using anything else will lead to uncertainty by all.
I think that you will end up confusing yourself if you try to play with figures, as in your post, to justify towing a particular van with a particular car and not use the standard kerb weight and mtplm.
However in the end it is up to you what ratio you are happy with and how you justify it.
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Agreed - dont worry about it, if you drive sensibly you wont know. I can pull my 3500kg trailer behind my 1500kg defender, well over 200% - yes not a caravan and yes scary as hell (which Is why I usually don't), but legal non the less.
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Peter, the outfit you are looking at looks fine. The caravan will have a plate showing the Maximum weight and therefore the maximum load you can carry; it is surprising how quickly this is used up, if you have a mover 30+ kgs, awning 25+kgs etc. Your car will have a maximum tow weight or train weight shown on the plate with VIN number etc and in the handbook. Not sure, but I think this is the legal limit for your car and anyway if exceeded could well invalidate any guarantee. Yes the 85% is a guide but quite sensible for inexperienced towers and is all about stabilty tail wagging the dog etc. Remember, noseweight is all important for stabilty and you should aim to be as close to the maximum (either car or van whichever is the lower) as possible most are 100kgs so 90 - 95kgs noseweight is ideal; also, weight distribution in the caravan is vital to stabilty, won't go into detail here as you can read all about it in the CC Handbook.
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It is certainly worth taking your fully laden van to a weighbridge. I was really surprised (perhaps shocked is a better word) the first time I did this year's ago. It made me aware of how easy it is to overload a caravan. I'm guessing, but I would think
that there are many caravans running overweight. I've also learnt not to rely on manufacturers weight, whether it is the listed MRO of the caravan or the weight of your extra chairs (according to the printed spec.) etc.When I buy a new caravan, the first thing I do is to upgrade the weight plate to maximum. This gives me a little more flexibility.
David
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Thanks everyone.
Yes, there is a weighbridge right next to where I live, and I've had my motorhome up a few times, so I know that the difference between our van being "almost empty with one person" to "almost full with 2 people" was about 200kg.
And since I know that both of those people, and lots of our stuff will be in a car instead of in a van, I'm struggling to see where 100+Kg is going to come from. We travel pretty light to be fair.
I'm really not trying to justify "cheating the rule". I'm just trying to understand what its trying to acheive so I can be confident in my own mind that it'll work ok.
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From a legal point of view the law will work on the MTPLM when assessing if an ojtfit is legal for the purpose of licence limitations and grpss train weight. This will be because after an accident it can be impossible to weigh them to get the actual weights
so they use the manufacturers figures so you are safe there although if you exceed the manufacturers figures and are stopped at a checkpoint you could still be caught there.93% is high but feasible but do not rely on the manufacturers weight being correct. Many people have weighed there caravans and found them higher than quoted so it is probably worth checking this.
Basically the lower the towing ratio the better and exceeding the kerb weight is simply not sensible.
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Most cars actually weigh well over any published kerb weight.
93% ratio is fine, i've towed over 90% for 5 years and find the rig more stable than the previous ratio which was slightly lower.
Fitting dampers and ATC are also worthwhile aids.
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Most cars actually weigh well over any published kerb weight.
93% ratio is fine, i've towed over 90% for 5 years and find the rig more stable than the previous ratio which was slightly lower.
Fitting dampers and ATC are also worthwhile aids.
What are dampers?
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Most cars actually weigh well over any published kerb weight.
93% ratio is fine, i've towed over 90% for 5 years and find the rig more stable than the previous ratio which was slightly lower.
Fitting dampers and ATC are also worthwhile aids.
What are dampers?
Also known as shock absorbers, but dampers is the correct term.
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When we talk about a damper in a caravan we normally mean the damper (shock absorber) in the breaking mechanism located in the A Frame by the handbreak. If this damper has gone you will know because you get a tremendous thud through the car as you break! A shock absorber is exactly the same as in a car and located by the road wheels. Not all caravans have them but is usually possible to retrofit them.
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... A shock absorber is exactly the same as in a car and located by the road wheels. Not all caravans have them but is usually possible to retrofit them.
But the point that Lutz was making, is that the correct name for a shocker/shock absorber is a damper
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Most cars actually weigh well over any published kerb weight.
93% ratio is fine, i've towed over 90% for 5 years and find the rig more stable than the previous ratio which was slightly lower.
Fitting dampers and ATC are also worthwhile aids.
What are dampers?
Also known as shock absorbers, but dampers is the correct term.
Ok. But what are they? Do they come with tow bars as standard? If not, could someone link to some examples?
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Went to the weighbridge yesterday, but with the car reasonable full. 2 adults & the bairn, plus a boot 3/4 full of stuff from a weekend trip away.
1760kg, compared to a published kerb weight of 1505kg
Will still go up again with the car totally empty except for me so I can get that number too
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Finally took the caravan over the weighbridge - Came up as 1270kg.
According to the noseweight gague I have, that is 65kg (got a spare wheel to go in the front locker yet - which will take me to close to my 75kg limit).
I assume for my MPTLM weight limit, I add those numbers together to get me to 1335kg?
Still, its a long way short of the 1400kg limit of the van. Only got the awning and groundsheet left to go in which would add another 20kg or so.
Fully packed, the car was 1870kg (including the noseweight pushing on it). So lets say its 1805kg vs 1335kg -- 74% ratio.
Apart from a nasty push-pull from a shot-damper (in for repair now) it tows perfectly straight. Which I'm delighted with.
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Fully packed, the car was 1870kg (including the noseweight pushing on it). So lets say its 1805kg vs 1335kg -- 74% ratio.
Ah, but the weight ratio that is compared with the recommended 85% is measured with an empty car, not fully packed and the fully laden caravan which in your case, as I understand it, would be 1400kg, so you will be a good deal greater than 74%.
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I tow at 95ish% with a Volvo V70 and don't notice any difference. As you say, when are you likely to tow a fully laden caravan with an empty car.
I used to tow a 3500kg trailer with our 2700kg Discovery 3, that was a trailer like a caravan and never had a problem even on extremely long down hill stretches of motorway in the Alps.
Personally I think the 85% rule is outdated but hey, who am I to say one way or another whether any one person should or shouldn't break that rule.
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Fully packed, the car was 1870kg (including the noseweight pushing on it). So lets say its 1805kg vs 1335kg -- 74% ratio.
Ah, but the weight ratio that is compared with the recommended 85% is measured with an empty car, not fully packed and the fully laden caravan which in your case, as I understand it, would be 1400kg, so you will be a good deal greater than 74%.
That's the thing. The max weight of a caravan is a bit arbitrary. You could have 2 vans that are indentical, and one can be plated 100kg higher than the other.
At the end of the day, you still put the same stuff in it.
The "golden ratio" doesn't seem to be anything more than a rough guide to me.
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Fully packed, the car was 1870kg (including the noseweight pushing on it). So lets say its 1805kg vs 1335kg -- 74% ratio.
Ah, but the weight ratio that is compared with the recommended 85% is measured with an empty car, not fully packed and the fully laden caravan which in your case, as I understand it, would be 1400kg, so you will be a good deal greater than 74%.
That's the thing. The max weight of a caravan is a bit arbitrary. You could have 2 vans that are indentical, and one can be plated 100kg higher than the other.
At the end of the day, you still put the same stuff in it.
The "golden ratio" doesn't seem to be anything more than a rough guide to me.
True, but to make any sense at all, one has got to agree on a common method of calculating weight ratio or your figures wouldn't be comparable with anyone else's. Besides, caravans are very often loaded right up to their MTPLM (if not, beyond) so it makes sense to use the true MTPLM figure. He who has the otherwise identical caravan, but plated 100kg higher, will probably have bought it with the intent of making full use of those 100kg.
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I tow at 95ish% with a Volvo V70 and don't notice any difference. As you say, when are you likely to tow a fully laden caravan with an empty car.
I used to tow a 3500kg trailer with our 2700kg Discovery 3, that was a trailer like a caravan and never had a problem even on extremely long down hill stretches of motorway in the Alps.
Personally I think the 85% rule is outdated but hey, who am I to say one way or another whether any one person should or shouldn't break that rule.
As someone who investigated accidents I do not accept that the 85% figure is outdated but it is advice for beginners. As you get more experienced you can exceed this although personally I think 90% is enough for most combinations.
The idea that higher weights are in order because the car is always at least partly loaded is wrong. The 85% takes account of this to build in a larger safety margin.
The other point that a combination is good because you have not had a problem is also not valid. The problem with this is you only find out if a combination is safe is if you have a real emergency and then if you are wrong it could be to late.
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Fully packed, the car was 1870kg (including the noseweight pushing on it). So lets say its 1805kg vs 1335kg -- 74% ratio.
Ah, but the weight ratio that is compared with the recommended 85% is measured with an empty car, not fully packed and the fully laden caravan which in your case, as I understand it, would be 1400kg, so you will be a good deal greater than 74%.
That's the thing. The max weight of a caravan is a bit arbitrary. You could have 2 vans that are indentical, and one can be plated 100kg higher than the other.
At the end of the day, you still put the same stuff in it.
The "golden ratio" doesn't seem to be anything more than a rough guide to me.
True, but to make any sense at all, one has got to agree on a common method of calculating weight ratio or your figures wouldn't be comparable with anyone else's. Besides, caravans are very often loaded right up to their MTPLM (if not, beyond) so it makes
sense to use the true MTPLM figure. He who has the otherwise identical caravan, but plated 100kg higher, will probably have bought it with the intent of making full use of those 100kg.I understand the need for a "failsafe" rule of thumb, but with most things in life, its "understanding" the purpose of a measure that makes it credible.
Is this ratio meant to give a certain value in real life, for example? If so, then what is it? Without a more nuianced thought-process behind it, this headline figure is nothing short of nonsense because 2 outfits could be exactly the same ratio when on
the road, but massively different according to this golden ratio.If this thought-process is shared, then people can look at the figures and work it out for themselves if they are of a mind to.
There is a point when saftey must give way to practicality. Otherwise we might as well arrange a trailer to move our caravans each weekend.
Creating "rules" like these will put a lot of people off caravanning, when the reality is, there's rarely a black-and-white answer when it comes to things like this that have so many variables.
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I tow at 95ish% with a Volvo V70 and don't notice any difference. As you say, when are you likely to tow a fully laden caravan with an empty car.
I used to tow a 3500kg trailer with our 2700kg Discovery 3, that was a trailer like a caravan and never had a problem even on extremely long down hill stretches of motorway in the Alps.
Personally I think the 85% rule is outdated but hey, who am I to say one way or another whether any one person should or shouldn't break that rule.
As someone who investigated accidents I do not accept that the 85% figure is outdated but it is advice for beginners. As you get more experienced you can exceed this although personally I think 90% is enough for most combinations.
The idea that higher weights are in order because the car is always at least partly loaded is wrong. The 85% takes account of this to build in a larger safety margin.
The other point that a combination is good because you have not had a problem is also not valid. The problem with this is you only find out if a combination is safe is if you have a real emergency and then if you are wrong it could be to late.
Again, this 85% ratio only makes sense if all vans have the same idea when it comes to payload, and when all cars measure their kerbweight in exactly the same way.
Otherwise, you are discounting perfectly safe setups because of a rule that is designed to be unrealistic from the start.
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As someone who investigated accidents I do not accept that the 85% figure is outdated but it is advice for beginners. As you get more experienced you can exceed this although personally I think 90% is enough for most combinations.
The idea that higher weights are in order because the car is always at least partly loaded is wrong. The 85% takes account of this to build in a larger safety margin.
The other point that a combination is good because you have not had a problem is also not valid. The problem with this is you only find out if a combination is safe is if you have a real emergency and then if you are wrong it could be to late.
There's no denying that the heaviest possible car towing the lightest possible caravan ensures optimal stability, but I would challenge anyone to be able to detect a weight ratio difference of only 5% in the way an outfit handles, all other criteria remaining equal.
As the transition between potentially stable to potentially unstable is gradual I would hate to put a figure on when one would begin to notice a difference, but engineering judgment tells me that 10% is about the minimum before an experienced driver would be able to detect any change in stability.
As no-one on the Continent has ever heard of an 85% recommendation and towing on right the limit is standard practice there, and yet one doesn't see their roads littered with caravans being involved in accidents, I think it is legimate to question the validity of the recommendation.
Under extreme conditions any outfit can be unsafe, even one with a weight ratio of, say, just 50%.
Perhaps one should put numbers aside and simply recommend the biggest possible weight differential between towcar and caravan that will still suit one's needs.
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I know people do not fully agree with me but the caravan accidents I have been involved with where the caravan has taken control have involved cars well over 90% or even over 100%. I accept that I have only seen a small proportion but it has convinced me.
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I know people do not fully agree with me but the caravan accidents I have been involved with where the caravan has taken control have involved cars well over 90% or even over 100%. I accept that I have only seen a small proportion but it has convinced me.
I have no doubt that your observations are correct, but what about the accidents occurring with outfits at 85% or under?
Your reply seems to suggest that one is confronted by a recipe for certain disaster if 85% is exceeded - as if one were to drop into a big black hole. I am sure that is not the case. If it were, the legal weight ratio requirement in Germany for towing at 100km/h (the only country that I know of that has such a requirement) would not be 100% (subject to other conditions being fulfilled, as well).
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I know people do not fully agree with me but the caravan accidents I have been involved with where the caravan has taken control have involved cars well over 90% or even over 100%. I accept that I have only seen a small proportion but it has convinced me.
90-100% of what though? That's the thing. The measures being recommended here don't make sense.
What is the purpose of the measure. Until we really understand what the "science" of this is, we are following like sheep.
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90-100% of what though? That's the thing. The measures being recommended here don't make sense.
What is the purpose of the measure. Until we really understand what the "science" of this is, we are following like sheep.
I don't think anyone responsible for promoting the 85% weight ratio recommendation ever laid claim to it being very scientific. It's more of a 'sensible guess' thing.
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