How to calculate compatibility

[JanBn]

Hi
We’re tentatively looking at different tow cars as we need to change my husband’s motorbility car later in the year. When it comes to working out the compatibility of the tow car with my Caravan it gets very confusing. I found a X1 220d xdrive 175bhp with towing capacity of 2000kg but when I asked CMC they said it was a 95% match as the tow ball limit was 75kg.
Now looking at other cars, but can anyone tell me the simple calculation of working out if a car is compatible as I’m finding it very frustrating trying to find information online.
My caravan is a Compass Camino 550, MTPLM of 1526kg. It is currently ‘downplated’ to 1476kg to be compatible with my Honda CR-V 1.6 i-dtec 4WD auto towing limit of 1500kg, towball limit 100kg.

I want to ‘up plate’ the caravan to the normal weight of 1526kg as working with only a 103kg payload at present, is very limiting.

So if anyone can give me a straight forward formula for working out the percentages of the tow car to Caravan safe limits including what effect the tow ball limit has on the choice of car I would be so grateful :cheer:
Thank you

 

[Woodentop]

175bhp will be no problem to most vans.

It is usual advice that the noseweight should be 5-7% of the MTPLM so that would put you a little overweight. Ergo working backwards for 75Kg on the nose the van needs to be no more than 1500Kg all up (5% of 1526Kg is 76.3Kg.)

Having said that I've just looked at the CMC tables of noseweights and it looks as though someone who cannot read replied to your query. The 1 series - that is a car - is rated 75Kg, but the X1 that you have is rated 80Kg so a 5% match is easily capable.

The towing 'match' on the other hand is based on the kerb weight of the towcar, which for your X1 is 1540Kg minimum (different manufacturers work it out in different ways,) so if your caravan is 1526Kg your will be running at 99% maximum. If you are experienced at towing this will not be a problem - the 85% you often see is only a guide for newcomers to towing, once you have been at it for a few years 100% is not an issue any more.

If you need to reduce noseweight just move some (preferably heavier) items from the front of the caravan to place them over the axle, or put them in the towcar boot.

Note that your BMW will likely have a breakaway cable eye or loop on the towbar itself - you should use this in preference to looping round the ball. Also make sure that the supplier has specifically been told to provide wiring on the towbar for battery charging and for the fridge. By default European electrics do not come with this wiring and it is an extra.

 

[ProfJohnL]

Hello JanBan,

There are a few pieces of generalised guidance that are designed to give caravanners a helping hand in matching car and caravan.

These are only guidance and at no time can they be used to exceed any statutory limits of either car or caravan.

The industry guidance suggests

1. The MTPLM of the caravan should not exceed 85% of the kerb weigh of the car. As towing experience is gained, this % may increase but should not exceed 100%

2. Caravans nose weight should be between 5 and 7% of the caravans MTPLM.

3. Keeping the heaviest items of load inside the caravan closest to teh caravans axle to reduce moments of inertia.

4. The car should have a minimum of 40BHP per Tonne for the whole combination.

Remember this is only guidance, it was given several decades ago, and none of it takes into account the technical advancements or abilities of the components. Its the best we have got at the moment.

Importantly none of these provides any guarantee of safety. Safety is almost always in the hand of the driver,

Their ability to interpret road and weather conditions, judging time to accelerate,

The space and time needed on the road.

Being aware and driving defensively to protect themselves from the other road users.

To keep their car and caravan in fully road worthy condition,

Tyres in good condition and at the appropriate pressure for the load they are moving.

Remember that Speed is always a factor when instability is encountered, so look at speed limits as maximum limits not targets, and be prepared to drive slower.

A technical point concerning the X1. The EU regulation stipulate that the hitch must be specified to accept a static vertical nose load equal or greater than 25kg or 4% of the towed weight limit for the vehicle. which ever is greater 4% of 2000 = 80kg.

If the tow ball is only rated at 75kg, then it is not a legally compliant ball hitch or towbar assembly for the model of car.

 

[otherclive]

Hello JanBan,

There are a few pieces of generalised guidance that are designed to give caravanners a helping hand in matching car and caravan.

These are only guidance and at no time can they be used to exceed any statutory limits of either car or caravan.

The industry guidance suggests

1. The MTPLM of the caravan should not exceed 85% of the kerb weigh of the car. As towing experience is gained, this % may increase but should not exceed 100%

2. Caravans nose weight should be between 5 and 7% of the caravans MTPLM.

3. Keeping the heaviest items of load inside the caravan closest to teh caravans axle to reduce moments of inertia.

4. The car should have a minimum of 40BHP per Tonne for the whole combination.

Remember this is only guidance, it was given several decades ago, and none of it takes into account the technical advancements or abilities of the components. Its the best we have got at the moment.

Importantly none of these provides any guarantee of safety. Safety is almost always in the hand of the driver,

Their ability to interpret road and weather conditions, judging time to accelerate,

The space and time needed on the road.

Being aware and driving defensively to protect themselves from the other road users.

To keep their car and caravan in fully road worthy condition,

Tyres in good condition and at the appropriate pressure for the load they are moving.

Remember that Speed is always a factor when instability is encountered, so look at speed limits as maximum limits not targets, and be prepared to drive slower.

A technical point concerning the X1. The EU regulation stipulate that the hitch must be specified to accept a static vertical nose load equal or greater than 25kg or 4% of the towed weight limit for the vehicle. which ever is greater 4% of 2000 = 80kg.

If the tow ball is only rated at 75kg, then it is not a legally compliant ball hitch or towbar assembly for the model of car.

Wooden top above had identified that the X1 noseweight is 80kg. This needs to be confirmed from the vehicle owners manual the best reference.

 

[JanBn]

Thank you ProfJohnL for that information, I will try and calculate any other tow cars we have in mind following that advice. I agree that speed limits are definitely that....limits...and not the norm, especially if weather or road conditions don't allow, only wish everyone stuck to that, whilst driving at 55mph towing my caravan on a motorway recently, a car with caravan in tow overtook me at such speed (much more than 60mph) it sucked my caravan over slightly, but luckily I sensed him in the middle lane and took my foot off the gas so was slowing down when he passed me one of the reasons I have a dash cam on my windscreen :dry: . You expect it of impatient car owners, but not a fellow caravanner
But back to the tow car compatibility, we are looking at other cars now, the Nissan X-Trail and the VW Sharon to name a few, so will try and work out the percentages for those. Thanks again for your great advice

Hello JanBan,

There are a few pieces of generalised guidance that are designed to give caravanners a helping hand in matching car and caravan.

These are only guidance and at no time can they be used to exceed any statutory limits of either car or caravan.

The industry guidance suggests

1. The MTPLM of the caravan should not exceed 85% of the kerb weigh of the car. As towing experience is gained, this % may increase but should not exceed 100%

2. Caravans nose weight should be between 5 and 7% of the caravans MTPLM.

3. Keeping the heaviest items of load inside the caravan closest to teh caravans axle to reduce moments of inertia.

4. The car should have a minimum of 40BHP per Tonne for the whole combination.

Remember this is only guidance, it was given several decades ago, and none of it takes into account the technical advancements or abilities of the components. Its the best we have got at the moment.

Importantly none of these provides any guarantee of safety. Safety is almost always in the hand of the driver,

Their ability to interpret road and weather conditions, judging time to accelerate,

The space and time needed on the road.

Being aware and driving defensively to protect themselves from the other road users.

To keep their car and caravan in fully road worthy condition,

Tyres in good condition and at the appropriate pressure for the load they are moving.

Remember that Speed is always a factor when instability is encountered, so look at speed limits as maximum limits not targets, and be prepared to drive slower.

A technical point concerning the X1. The EU regulation stipulate that the hitch must be specified to accept a static vertical nose load equal or greater than 25kg or 4% of the towed weight limit for the vehicle. which ever is greater 4% of 2000 = 80kg.

If the tow ball is only rated at 75kg, then it is not a legally compliant ball hitch or towbar assembly for the model of car.

 

[Hutch]

I agree that speed limits are definitely that....limits...and not the norm, especially if weather or road conditions don't allow, only wish everyone stuck to that, whilst driving at 55mph towing my caravan on a motorway recently, a car with caravan in tow overtook me at such speed (much more than 60mph) it sucked my caravan over slightly, but luckily I sensed him in the middle lane and took my foot off the gas so was slowing down when he passed me one of the reasons I have a dash cam on my windscreen :dry: . You expect it of impatient car owners, but not a fellow caravanner

Hi Jan, I totally agree with you on the speed thing, I have noticed other caravanners doing the same thing, I think maybe because, as we go along at say 55 mph on the Speedo on the car , which may be in reality say 52 mph, whilst Zippy is reading 60 mph from his SatNav and his speedo would be reading say 64mph so in reality a difference of 8 mph and a lot of wind disturbance.
Anyway safe touring.

 

[Raywood]

I agree with almost all the advice given here except the idea of a 95% ratio. There are a few combinations where this will work but as a general rule it is too high. Personally I would try and limit the ratio to around 90% and certainly not go beyond 95. You cannot try the combination before buying so you must err on the safe side as if the combination does not work well you are stuck with it for some time or you will have to downsize the caravan.
Your safety comes first so do not take risks with a too high towing ratio.

 

[Lutz]

If you can detect the difference in the way an outfit handles when the weight ratio is increased (or decreased) by 5% or less, all other criteria remaining unchanged, you're a better driver than me and I've been towing caravans for almost 30 years in retrospect much of the time at around 100%, although I never bothered to check beforehand. I only went by the maximum allowable towload as the limit.

Incidentally, why was the caravan 'downplated' in the first place? If the caravan was originally plated at 1526kg and the car had a max. towload of 1500kg, then so long as the noseweight exceeded 26kg it would never have exceeded any limits. The towed load is, after all, not the total weight of the caravan but only its axle load, so if you made full use of the 100kg noseweight limit, you would actually only be towing 1426kg even with the caravan at its 1526kg MTPLM.

By the way, what is the MTPLM that is quoted on the weight plate in the front locker? Does that tie in with the one next to the door?

 

[JanBn]

Oh ok.....because I’ve only been towing for 10 months, I’ve only ever gone by what I’ve been told or advised is right. The reason the caravan was downplated was because the dealer said he could not sell us a Caravan who’s MTPLM exceeded our car tow limit. So I read in the small print that when the Caravan went to build, we could request it to be downplated or up plated in 50kg blocks. Also if we changed our car to a higher tow limit within three years of purchase, they will change the MTPLM back up to it’s original plate of 1526kg FOC.
Regarding the plate in the locker you mentioned, I was not aware there was one, I will check that out in daylight tomorrow.

Thank you for your information.

If you can detect the difference in the way an outfit handles when the weight ratio is increased (or decreased) by 5% or less, all other criteria remaining unchanged, you're a better driver than me and I've been towing caravans for almost 30 years in retrospect much of the time at around 100%, although I never bothered to check beforehand. I only went by the maximum allowable towload as the limit.

Incidentally, why was the caravan 'downplated' in the first place? If the caravan was originally plated at 1526kg and the car had a max. towload of 1500kg, then so long as the noseweight exceeded 26kg it would never have exceeded any limits. The towed load is, after all, not the total weight of the caravan but only its axle load, so if you made full use of the 100kg noseweight limit, you would actually only be towing 1426kg even with the caravan at its 1526kg MTPLM.

By the way, what is the MTPLM that is quoted on the weight plate in the front locker? Does that tie in with the one next to the door?

 

[ProfJohnL]

...because the dealer said he could not sell us a Caravan who’s MTPLM exceeded our car tow limit....

Oh dear,

The dealer is telling porkies. There is no law that "prevents" him from selling you the caravan under the given circumstances. He may be obliged to advise you the outfit is inappropriate or ill advised, but it is not the dealers prerogative to prevent a sale on that basis alone. Ultimately it is up to the driver of any vehicle or outfit to ensure the vehicle is legally compliant, and not unsafe.

In this specific case as Lutz has explained the caravan in question was not in excess of the tow vehicle towed weight limit refers to the trailers axle load not its MTPLM. In fact the towed weight is the real actual measured value not the weight limit of the trailer. So in practice you could to an empty or partially loaded trailer whose measure weight is within the limit of the vehicle, even if its MTPLM is greatly over.

Where the MTPLM does play a part is in the definition of the driver licence, where there requirement looks at the weight capacities defined by the weight limits of car and trailer.

However in the UK just becasue goods are displayed with a price, it only legally means the retailer is inviting customers to bid for the goods. a contract to sell is only established when both parties have agreed the price, and that technically means a seller does not have to accept an offer even if it matches the suggested price. What a seller cannot do is to refuse to sell on the basis of any prejudices defined in the equal opportunities legislation.

 

[JanBn]

Ahhh ok, I did think it strange, but because we were total novices, we adhered to what we were told. I rang one dealer asking about a caravan we fancied and he asked us what our car was, he said the computer calculations say it’s too heavy and his actual words were, “it’s above your limit” and when I enquired more about the purchase, he said I cannot sell it to you he was very abrupt and made me feel a bit stupid for not knowing the ‘law’ :dry:

I did wonder, after I bought my current caravan, if the factory weight without payload was 1373kg how would anyone know if I was going to carry anything in it or just load my car up with the stuff I intended to take :huh:

Ah well we live and learn by experience, thank you for taking the time to explain that to me, at least I know I can ‘up plate’ my caravan, and as long as I stay within my limit with my current tow car I’m not illegally on the road as I was led to believe.

...because the dealer said he could not sell us a Caravan who’s MTPLM exceeded our car tow limit....

Oh dear,

The dealer is telling porkies. There is no law that "prevents" him from selling you the caravan under the given circumstances. He may be obliged to advise you the outfit is inappropriate or ill advised, but it is not the dealers prerogative to prevent a sale on that basis alone. Ultimately it is up to the driver of any vehicle or outfit to ensure the vehicle is legally compliant, and not unsafe.

In this specific case as Lutz has explained the caravan in question was not in excess of the tow vehicle towed weight limit refers to the trailers axle load not its MTPLM. In fact the towed weight is the real actual measured value not the weight limit of the trailer. So in practice you could to an empty or partially loaded trailer whose measure weight is within the limit of the vehicle, even if its MTPLM is greatly over.

Where the MTPLM does play a part is in the definition of the driver licence, where there requirement looks at the weight capacities defined by the weight limits of car and trailer.

However in the UK just becasue goods are displayed with a price, it only legally means the retailer is inviting customers to bid for the goods. a contract to sell is only established when both parties have agreed the price, and that technically means a seller does not have to accept an offer even if it matches the suggested price. What a seller cannot do is to refuse to sell on the basis of any prejudices defined in the equal opportunities legislation.

 

[otherclive]

Ahhh ok, I did think it strange, but because we were total novices, we adhered to what we were told. I rang one dealer asking about a caravan we fancied and he asked us what our car was, he said the computer calculations say it’s too heavy and his actual words were, “it’s above your limit” and when I enquired more about the purchase, he said I cannot sell it to you he was very abrupt and made me feel a bit stupid for not knowing the ‘law’ :dry:

I did wonder, after I bought my current caravan, if the factory weight without payload was 1373kg how would anyone know if I was going to carry anything in it or just load my car up with the stuff I intended to take :huh:

Ah well we live and learn by experience, thank you for taking the time to explain that to me, at least I know I can ‘up plate’ my caravan, and as long as I stay within my limit with my current tow car I’m not illegally on the road as I was led to believe.

...because the dealer said he could not sell us a Caravan who’s MTPLM exceeded our car tow limit....

Oh dear,

The dealer is telling porkies. There is no law that "prevents" him from selling you the caravan under the given circumstances. He may be obliged to advise you the outfit is inappropriate or ill advised, but it is not the dealers prerogative to prevent a sale on that basis alone. Ultimately it is up to the driver of any vehicle or outfit to ensure the vehicle is legally compliant, and not unsafe.

In this specific case as Lutz has explained the caravan in question was not in excess of the tow vehicle towed weight limit refers to the trailers axle load not its MTPLM. In fact the towed weight is the real actual measured value not the weight limit of the trailer. So in practice you could to an empty or partially loaded trailer whose measure weight is within the limit of the vehicle, even if its MTPLM is greatly over.

Where the MTPLM does play a part is in the definition of the driver licence, where there requirement looks at the weight capacities defined by the weight limits of car and trailer.

However in the UK just becasue goods are displayed with a price, it only legally means the retailer is inviting customers to bid for the goods. a contract to sell is only established when both parties have agreed the price, and that technically means a seller does not have to accept an offer even if it matches the suggested price. What a seller cannot do is to refuse to sell on the basis of any prejudices defined in the equal opportunities legislation.

Jan you are correct that no one will know how much weight you load into a caravan. But you are doing the correct things by being conscientious and seeking advice. The only ones who will know what weight you put in are you (post weighbridge check) and VOSA/ Police if they pull you over for a roadside check. I have even been stopped totally at random and escorted to the VOSA weighbridge. Also when you look at new arrivals on site you will be amazed at what some folks fetch out of the front lockers and caravan, so I suspect that more than a few are over weight.

 

[Lutz]

It strikes me that the dealer didn't know what he was talking about, especially regarding his comment about "computer calculations", making it sound as though it is a very complex issue, whereas all the figures you need can be read directly off the statutory weight plates of both the car and the caravan. On top of that he should have known that the towload doesn't correspond to the total weight of the caravan, but only its axle load.
I'd be interested to know what the plate in the front locker says because that plate is the one that counts (if the caravan was built after introduction of whole vehicle type approval in 2013), not the one next to the door.

 

[Raywood]

A dealer is quite within his rights not to sell a caravan to you if he feels the combination would be unsafe, and I would applaud any dealer who does this. If a dealer knows the combination is potentially unsafe he must warn the prospective purchaser to protect himself against a claim, but he may feel this is still not enough. Dealers cannot refuse a sale on ethnic, religious, or similar grounds but that apart it is their choice as to whether they sell.

 

[Lutz]

A dealer is quite within his rights not to sell a caravan to you if he feels the combination would be unsafe, and I would applaud any dealer who does this. If a dealer knows the combination is potentially unsafe he must warn the prospective purchaser to protect himself against a claim, but he may feel this is still not enough. Dealers cannot refuse a sale on ethnic, religious, or similar grounds but that apart it is their choice as to whether they sell.

That would be a fair comment if the reason for not selling actually were a safety issue, but in the case in question it was because the dealer claimed that the outfit were "outside the limits", which simply was not the case.

 

[JanBn]

Haha :lol: you are right Otherclive, I’ve watched people take out just about everything you could fit in bar the spa jacuzzi :lol:

 

[JanBn]

Hi Lutz I’ve looked in my front locker for the plate you mentioned but the only thing I can find is my CRIS number plate. The caravan was built May last year, 2017. If that’s any help? :huh:

 

[Lutz]

Hi Lutz I’ve looked in my front locker for the plate you mentioned but the only thing I can find is my CRIS number plate. The caravan was built May last year, 2017. If that’s any help? :huh:

If the caravan was built in 2017 then that was after whole vehicle type approval came into being, requiring a statutory plate which must give details of the chassis number, MTPLM, maximum axle loads, the noseweight limit, type approval number and the manufacturer's name. More often than not this plate can be found in the front locker, but I understand some manufacturers locate it elsewhere. However it is legally required so it must be somewhere. If the plate that you are looking at doesn't show maximum axle loads, for example, it is not the statutory plate.

 

[JanBn]

Just checked the plate by the front door and it has the name of manufacturer, serial number, then four boxes with numbers starting with top box
0- 1476kg
1- 100kg
2- 1550kg
N/A kg

Then under that is Miro 1373kg
MTPLM 1476kg
Tire size. Tyre pressure
Wheel bolt torque
Is this the one you meant?

Ps the MTPLM should be 1526kg. It as I mentioned in main post we asked for it to be down plated by 50kg so we were ‘legal’ according to one of the dealers we spoke to :huh:

Hi Lutz I’ve looked in my front locker for the plate you mentioned but the only thing I can find is my CRIS number plate. The caravan was built May last year, 2017. If that’s any help? :huh:

If the caravan was built in 2017 then that was after whole vehicle type approval came into being, requiring a statutory plate which must give details of the chassis number, MTPLM, maximum axle loads, the noseweight limit, type approval number and the manufacturer's name. More often than not this plate can be found in the front locker, but I understand some manufacturers locate it elsewhere. However it is legally required so it must be somewhere. If the plate that you are looking at doesn't show maximum axle loads, for example, it is not the statutory plate.

 

[Lutz]

Just checked the plate by the front door and it has the name of manufacturer, serial number, then four boxes with numbers starting with top box
0- 1476kg
1- 100kg
2- 1550kg
N/A kg

Then under that is Miro 1373kg
MTPLM 1476kg
Tire size. Tyre pressure
Wheel bolt torque
Is this the one you meant?

Ps the MTPLM should be 1526kg. It as I mentioned in main post we asked for it to be down plated by 50kg so we were ‘legal’ according to one of the dealers we spoke to :huh:

Yes, that is the one. It looks as though Elddis have got things right. The reason why I asked was that I know of cases affecting Bailey caravans where the label next to the door doesn't agree with the statutory plate that they locate in the front locker.
Judging by the figures that you quote, in line with the allowable axle load, your caravan could even be uprated to 1550kg, unless Elddis have some plausible reason for limiting the MTPLM to 1526kg.

ps: I presume that the plate also gives details of the chassis and type approval numbers.

 

[Raywood]

I am not sure that downplating helps, as it is the actual weight that counts and taking 50kg off leaves you with a very small payload of about 100kg that is easily exceeded. If weight is a problem I would take the caravan empty to a weighbridge and see what the caravan weighs as the MIRO may be wrong, as it varies between caravans even of the same model. You will then know what weight you can load to keep you safe.

Just checked the plate by the front door and it has the name of manufacturer, serial number, then four boxes with numbers starting with top box
0- 1476kg
1- 100kg
2- 1550kg
N/A kg

Then under that is Miro 1373kg
MTPLM 1476kg
Tire size. Tyre pressure
Wheel bolt torque
Is this the one you meant?

Ps the MTPLM should be 1526kg. It as I mentioned in main post we asked for it to be down plated by 50kg so we were ‘legal’ according to one of the dealers we spoke to :huh:

Hi Lutz I’ve looked in my front locker for the plate you mentioned but the only thing I can find is my CRIS number plate. The caravan was built May last year, 2017. If that’s any help? :huh:

If the caravan was built in 2017 then that was after whole vehicle type approval came into being, requiring a statutory plate which must give details of the chassis number, MTPLM, maximum axle loads, the noseweight limit, type approval number and the manufacturer's name. More often than not this plate can be found in the front locker, but I understand some manufacturers locate it elsewhere. However it is legally required so it must be somewhere. If the plate that you are looking at doesn't show maximum axle loads, for example, it is not the statutory plate.

 

[Lutz]

I am not sure that downplating helps, as it is the actual weight that counts and taking 50kg off leaves you with a very small payload of about 100kg that is easily exceeded. If weight is a problem I would take the caravan empty to a weighbridge and see what the caravan weighs as the MIRO may be wrong, as it varies between caravans even of the same model. You will then know what weight you can load to keep you safe.

You are of course correct. It is the actual weight that counts when checking against the towload limit or the gross train weight, unless B+E driving licence entitlement is an issue or unless you are a strict follower of the so-called 85% weight ratio rule, in which case it is the plated MTPLM that counts, regardless of the actual weight. Downplating really only makes sense if one would otherwise exceed the 3500kg gross combination weight limit imposed on category B driving licence holders.