Payloads / Noseweights

[Gareth_5080562]

I am considering purchasing a Fleetwood Volante 560-4 to be towed by a Mercedes C220CDI.

The van is a little heavy (but Legal) if loaded to the full MTPLM of 1460Kg (the cars Kweight being 1540Kg), but I plan to observe the 85% guidelines by restricting payload to c80Kg in the caravan thus restricting towing weight to c1310Kg. The car will have max payload of c250Kg after allowing for passengers.

Taking account of the guideline on noseweight at 7% of MTPLM this would give a noseweight of 102Kg (92Kg at the restricted laden weight of 1310Kg). My cars handbook gives a max noseweight of 75Kg (fairly standard for most cars other than 4x4's it seems)

Being new to caravaning I have a number of questions :

1. From your experience do you think the imposed payload restrictions will allow for sufficient equipment/personal effects to be carried

2. Should I load the caravan so that the noseweight is no heavier than 75Kg - i.e 5.7% of the restricted laden weight. Would this be stable?

3. My cars boot has a weight capacity of 100Kgs. Is this in addition to the 75Kg tow bar weight limit? Sorry if this is a silly question but as both are behind the rear axle it seems to me it might be one or other but not both!

Thanks for your advice

 

[Lutz]

I think you will have to exercise an awful lot of self-control to keep the payload in the caravan to 80 kg. From my experience of what one is tempted to take along on holiday, one is grateful for every kg payload available.

You ask whether you should not exceed the 75kg noseweight specified. You MUST not exceed 75kg. It is a legal limit, as is the maximum permissible towing load (which, from memory, is about 1800kg for a Merc C220).

I don't know where you got that figure of 100kg boot load for your car from. Is that with a full load of occupants? What is important is that you do not exceed the maximum gross vehicle weight specified by the manufacturer and the 75kg noseweight is included in that figure. So, if you reach the permitted gross vehicle weight with 100kg in the boot, then 75kg is part of that load. However, 100kg maximum payload in the boot does seem rather low to me for a Mercedes C220.

 

[VIP2006]

I have recently changed my Mercedes C220 CDI Auto for a Mercedes ML270. the main reason for this is

1 - That whilst the car can tug up to 1500Kgs. and that the max noseweight of 75Kgs matched the max noseweight of the van and the vans MTPLM was 1250Kgs I felt that the car was to streamlined for towing.

1 - that the car offered very low boot capacity when endevouring to balance the weight between the vehicles.

The C220CDI is a grand economical car and is a pleasure to drive but I do not rate it as a tow vehicle and much of the time that I towed with it I felt that if a snake occured the tail would wag the dog (the dog being the car).

Having experienced a snake before I felt that the heavier the car the better thus I have changed to the Mercedes ML270 CDI Auto. I have towed my van only once since aquisition and felt a great deal more comfortable knowing that the weight of the car {3500Kgs) would not allow the van to control the car if a snake occured. IMHO

 

[Lutz]

I just checked and found out that the C220CDI has a total max. permissible payload of 480kg (460kg if automatic), so the total weight of all occupants (in addition to the driver, who is included in the kerbweight) and luggage in the car would be 405kg or 385kg respectively, if the noseweight is 75kg.

 

[JasonSDunks]

Lutz,

Question for you: car: Peugeot 407 1.6 hdi KW 1500; max tow 1300; NW 65. van:ace jubilee viceroy miro 1167, mtplm 1392. 85% weight 1275 giving payload in van of 108kg.

Obviously cannot tow at mtplm, but with careful loading can achieve the 1275.

If we follow the above is this a legal tow?

 

[ProfJohnL]

Hello Jason,

Tecnically yes. However you may have a little more leaway than you thought. Firstly the 85% is only guideline, though it is a sensible target. The 407 withits 1300Kg max tow weight is only 87% and should be perfectly acceptable. giving a payload of 133Kg.

What you have to consider is that items such as gas bottles battery, kitchen utensils power cables etc are part of the payload, so your 133 will easily be swallowed up.

There is another twist that may be in your favour regarding the nose load. Lutz seems to have the handle on this so hopefully he will respond.

 

[JasonSDunks]

Thanks John.

Have only towed once and still get worried about the weight issue.

J

 

[JasonSDunks]

Sorry, the nosewieght for the 407 is 60kg. Doh!

J

 

[Lutz]

How did you arrive at 133 payload, John L? If the maximum towload of the Peugeot 407 is 1300kg, then the maximum MTPLM of the caravan would be 1300 plus the noseweight (60kg in Jason's case), i.e. 1360kg. The maximum payload of the caravan is therefore 1360 - 1167 = 193kg.

 

[JasonSDunks]

Thanks Lutz.

Just to clarify; Max tow of my car is 1300 (handbook) however I can add the nose weight to this, therefore my car can tow 1360kg legally?

J

 

[Lutz]

The towload that the car manufacturer specifies is the axle load of the trailer/caravan. The total weight of the caravan is, however, the axle load PLUS the noseweight. Hence, in your case, you may tow a caravan with an MTPLM of 1300 + 60 = 1360kg.

 

[JasonSDunks]

Cheers Lutz.

J

 

[ProfJohnL]

Hello Lutz,

Jason's question and your most recent reply have raised my concern about the way trailer and outfit mass calculations are used, and in particular the interpretation you have placed on them.

I think it is important to understand the difference and interaction of the properties of matter with regard to their mass, and the resultant force caused by gravity commonly known as weight. I do wonder if these differences have been incorrectly exchanged in some calculations.

If we refer to the accepted criteria and their definitions for road vehicles, the standardised EU system now uses references in MASS rather than weight.

(e.g. Mass In Running Order, Maximum Technically Permitted Laden Mass e.t.c.)

By definition Weight is specifically a gravitational force generated between two masses. In our case of course one mass is the earth, and the other is any object or caravan.

Now, my specific concern is with the tow ball and the car manufacture's Maximum Permitted Towed Mass for any given vehicle. This is quoted as a mass (in Jason's case 1300Kg) The permitted nose load is a force, (60Kg for Jason).

The maximum mass allowed to be towed is based on the manufactures assertion that the equipment will withstand the forces generated by towing. As the forces will primarily be created by the inertia of the trailer, then the mass of the trailer is the most significant feature. To increase a trailers mass beyond the permitted limit will therefore be illegal.

To generate Jason's 60Kg nose load, it is necessary to adjust the loading of the trailer so that the Centre of gravity is moved forward of the main axle to generate a turning force to be supported by the towball. The overall mass of the trailer has not changed.

If the trailer is loaded to 1300Kg and yet does not provide the require nose load, you seem to suggest, you are permitted to add addition mass to the trailer to create the nose load, then whilst you may generate the nose load you have also increased the overall mass. As any mass would have to be added within the body of a caravan, to because of the mechanical leverage you would have to add considerably more than 60Kg mass to achieve 60Kgf at the tow hitch. This in my opinion is unsafe as it now exceeds the manufactures specification for maximum permitted mass.

I think you are wrong to suggest that you add the equivalent nose down force on top of the manufactures maximum permitted mass to create extra payload capacity.

John L

 

[Lutz]

I sometimes use the term weight rather than mass because weight is more familier but you are right, mass is the correct term. Personally, I prefer the term towing load but even the EU directive 92/21/EEC talks about towable mass. In order to avoid possible scope for my interpretation, here is the actual wording of the definition of 'towable mass', as stated in Annex II Article 2.6 of the directive:

"Towable mass means the mass of the trailer towed excluding the vertical load on the coupling point of the towing vehicle."

I think that is pretty clear and in line with what I have been saying all along. The vertical load on the coupling point is what is commonly referred to as the noseweight.

 

[ProfJohnL]

Hello Lutz,

Thank you for quoting the directive, I assume you have not altered the wording.

I too am guilty of mixing the terms Mass and weight when replying to postings. Having taken more time to analyse the subject, I can see some quite specific reasons why it is important to differentiate corrctly between the terms Mass and weight, and also why the trailer directives are quite deliberate and correct in the terms they choose to use.

I have come across many instances of legalised wording in standards and directives realting to gas products, and found that you have to be very careful when using the information. My analysis of this statement is that they refer to the towable MASS, but they then refer to the vertical LOAD on the coupling point. They use the word load becuase it is a force that has an effect, but they also use it to deliberatly break the link with concept of Mass.

The vertical load on the coupling point is generated (as I described) by the turning forces due to the position of the centre of gravity realtive to the main axle and the tow hitch.It is possible to change the vertical coupling load on any given trailer by adjusting the position of the payload.

As the load is only a force and has no mass uniquely associated with it, it cannot affect the mass of the trailer. To avoid confusion they tell you to ignore the coupling load when assessing the mass of the trailer. They do not say add or subtract the value, as that cannot occur because they are not similar measurands.

I believe it is unsafe to assume you can add the vertical coupling vector force as an equiuevalent scalar mass value on top of the maufactures MTPLM. I strongly suspect that your argument would fail if challengd in court for the reasons stated above.

I sincerly suggest that you refrain from perpetuating the concept of adding vertical coupling load to the available payload on trailers.

John L

 

[Lutz]

Hello John,

I appreciate your concern but I am afraid you are confusing two definitions. You state, and I quote:

"I believe it is unsafe to assume you can add the vertical coupling vector force as an equiuevalent scalar mass value on top of the maufactures MTPLM. I strongly suspect that your argument would fail if challengd in court for the reasons stated above."

I have never said that one can add anything on top of the manufacturer's MTPLM. The MTPLM is the absolute maximum mass of the trailer (or caravan) and may not be exceeded under any conditions. However, this mass is the sum of the axle load and the vertical coupling force. Don't forget that when the trailer is on the weighbridge to determine its total weight (or mass) it is supported at 3 points - 2 wheels and the coupling (or jockey wheel). As the towable mass is defined as the axle load (re. my last posting) that means that the load at the third point is part of the MTPLM but NOT part of the towing load.

This is not illogical because the vertical force on the coupling is counted as part of the payload of the towing vehicle. If it were included in the towing load as well, the noseweight would effectively be counted twice, once as part of the GVW of the car and again as part of the towing load.

As I have said so many times before, and as confirmed by the wording of the directive, the towing load IS NOT the total mass of the trailer but only its axle load. Therefore, one cannot compare car manufacturers' max. towing loads directly with the caravan manufacturers' quoted MTPLM without making allowances for the noseweight. It would not be correct to put just the wheels of the caravan on a weighbridge and say that the resultant measurement is the weight (or mass) of the caravan. If you did, you could exceed the MTPLM by the amount of the noseload.

 

[Lutz]

Hello John,

I appreciate your concern but I am afraid you are confusing two definitions. You state, and I quote:

"I believe it is unsafe to assume you can add the vertical coupling vector force as an equiuevalent scalar mass value on top of the maufactures MTPLM. I strongly suspect that your argument would fail if challengd in court for the reasons stated above."

I have never said that one can add anything on top of the manufacturer's MTPLM. The MTPLM is the absolute maximum mass of the trailer (or caravan) and may not be exceeded under any conditions. However, this mass is the sum of the axle load and the vertical coupling force. Don't forget that when the trailer is on the weighbridge to determine its total weight (or mass) it is supported at 3 points - 2 wheels and the coupling (or jockey wheel). As the towable mass is defined as the axle load (re. my last posting) that means that the load at the third point is part of the MTPLM but NOT part of the towing load.

This is not illogical because the vertical force on the coupling is counted as part of the payload of the towing vehicle. If it were included in the towing load as well, the noseweight would effectively be counted twice, once as part of the GVW of the car and again as part of the towing load.

As I have said so many times before, and as confirmed by the wording of the directive, the towing load IS NOT the total mass of the trailer but only its axle load. Therefore, one cannot compare car manufacturers' max. towing loads directly with the caravan manufacturers' quoted MTPLM without making allowances for the noseweight. It would not be correct to put just the wheels of the caravan on a weighbridge and say that the resultant measurement is the weight (or mass) of the caravan. If you did, you could exceed the MTPLM by the amount of the noseload.

Perhaps an example out of my own experience will serve to make the issue clearer. I used to have a car with a max. permissible towload of 1300kg and and caravan with an MTPLM of 1300kg. While on my way on holiday, I once ran into a police check. They put the caravan (while hitched up to the car) on the scales and measured 1430kg at the wheels. I was therefore 130kg over the maximum permissble towload but 205kg over the MTPLM (assuming 75kg noseweight). Fortunately, the police didn't concern themselves with the MTPLM and refrained from further action after I emptied the on board water tank and moved a couple of heavy items into the car. However, ever since that incident I made towing weights a pet subject of mine.

 

[JasonSDunks]

Lutz & John L

Now I am confused!

If I load my caravan to 1280 kg, that is around 85% of the 407 KW and within the 1300 kg tow load I will be ok. I know that I can then add around 120 kg in 'stuff'. This will keep me legal and a good towing balance provided I can get to 60kg nose weight.

Thanks for you help.

J

 

[Lutz]

Sorry to have confused you, Jason, but yes, you'll be OK. The discussion that I had with John centres around legal weight limits for both car and caravan but you will be well within these limits if you stick to loading your caravan to 1280kg. Just don't forget that if you want to check its weight, it has to be measured in the unhitched condition and the jockey wheel must be standing on the scales, too.

 

[ProfJohnL]

Hello Lutz & Jason,

Jason Ignor our detailed discussion, as Lutz says you should be fine.

Lutz I havn't dissapeared yet, (though I do have to go into hospital soon for some serious sugery).

Thank you for clarifying your position on MTPLM and coupling load, We agree that the MTPLM must not be exceded. I also agree that the coupling load should not be considered twice, but I have yet to confirm your interpretaton of the the "towable mass".

I am still reviewing the EU Directives, but the site has just gone of line, so I will have to revisit.

Cheers. John L

 

[Lutz]

I am very sorry to hear of your impending surgery. I wish you you well and hope that you recover quickly.

I'd just like to add that the EU Directive always refers to measurements in the static condition and I assure you that I have copied the actual wording regarding the definition of towable mass out of the original text.

 

[WatsonJohnG]

Good luck John

Towable mass could be weighty subject

We will pray for enlightened guidance from the prophet Lutz

Regards

 

[JasonSDunks]

Thanks for your help guys.

J