Colin,

I understand what you are saying, and am happy to accept that your definition is correct.

That said, whenever I have looked at compliance plates on vans, it is a strange coincidence that the GTM printed on the plate always appears to equal the ATM (ie builder allocated rating) less the actual ball weight at Tare (the only ball weight available to them). I am yet to see a GTM that bears any scientific or other obvious relationship to the axle limits.

This is to be expected of course, due to the fact that the only actual weights available to the manufacturer will be the Tare and Actual Ball weight at Tare. They then apply their magic formula to give a load allowance (sometimes based on engineering and sometimes on some black magic guess), which when added to the Tare gives the ATM rating. Of course, as no loaded ball weight is available to give a true GTM rating, they then use the Empty ball weight instead, as generally this will give a workable GTM as the ball weight will increase with load, and the ACTUAL loaded ball weight will mean the axle loaded mass will be less than the GTM stated .

It appears that this may be the reason why people state that ATM less GTM equals Ball weight ATM less ball weight equals GTM. Because compliance plates show that the figures quoted on it agree with that definition.

I am not making this comment to enter an argument, but as long as people see compliance plates that give figures that show ATM less the ball weight is equal to the quoted GTM, the "mistake" you talk about will continue to be perpetuated.

As for this being the cause of much litigation for builders, I suspect a bigger problem is the inability of some builders to get the compliance plate weights correct at the factory, if customer stories are believed.

I"m sorry Colin but you are wrong with regard ATM and GTM. ATM is the plated maximum all up weight of the van on its own. GTM  is NOT a fixed mas but is the weight on the axles of the van when coupled to the tow vehicle. Therefore it is always (ATM - GTM equals towball mass). GTM is a variable according to van loading and is not a FIXED mass by the manufacturer. ATM on the other hand is a fixed mass by the manufacturer and is not alterable. Hence tow ball mass varies likewise with van loading. `

Alan

-- Edited by Brenda and Alan on Friday 23rd of February 2018 12:18:46 AM

-- Edited by Brenda and Alan on Friday 23rd of February 2018 12:19:28 AM

Colin,
I think you are well aware of my position on this subject, we both discussed it at lenght on another forum.
I am not about to ramble on here about it all again other than to say that GTM as plated is calculated by the manufacturer when he subtracts the measured ball weight from the rated ATM. It is not, in my view, a rating nor is there any legal requirement under VSB1 for a manufacturer to stamp a GTM number on the plate at all.

There are 5 ratings that people should know about relating to a caravan combination.
They are ATM, GVM, GCM and tug Ball Rating and tug BTC.

One other rating that will be stamped somewhere on the caravan, sometimes on the comp plate, is the Axle Group Rating and this is in fact the real "GTM rating". It is set by the chassis/suspension manufacturer.

The only rating that is legally required to be stamped on a caravan compliance plate is the ATM. All other weight information is optional.

Radar wrote:

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montie wrote:

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Colin,
I think you are well aware of my position on this subject, we both discussed it at lenght on another forum.
I am not about to ramble on here about it all again other than to say that GTM as plated is calculated by the manufacturer when he subtracts the measured ball weight from the rated ATM. It is not, in my view, a rating nor is there any legal requirement under VSB1 for a manufacturer to stamp a GTM number on the plate at all.

There are 5 ratings that people should know about relating to a caravan combination.
They are ATM, GVM, GCM and tug Ball Rating and tug BTC.

One other rating that will be stamped somewhere on the caravan, sometimes on the comp plate, is the Axle Group Rating and this is in fact the real "GTM rating". It is set by the chassis/suspension manufacturer.

The only rating that is legally required to be stamped on a caravan compliance plate is the ATM. All other weight information is optional.

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 Hi Montie

What is BTC? ,     maybe "ball towing capacity."

And once again please write in full not the abbreviated version. Our partners have trouble understanding.

That is interesting the "only legal requirement is axle group weight" because I have just paid out for a new vin plate with an extra 100kg payload which brings the gross loading up to the same figure as the axle group weight. 

Eg. Ball weight of 270kg plus the 2750kg axle group weight equals 3020kgs. Mine you I would be hard pressed to get any more weight in the caravan as the axle group is towards the back and any weight added to the caravan falls directly onto the towball but this theory makes my set up really legal and maybe I needed not to of pay out for the new vin plate if it had not had unnecessary figures on the vin plate.

To Colin and the Caravan Council "what do you say about all this, what is the legal requirement on the vin plate?"

-- Edited by Radar on Saturday 24th of February 2018 08:49:58 AM

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 Braked Towing Capacity

Gross Vehicle Mass

Gross Combination Mass

Aggregate Trailer Mass

I will post an extract of VSB1 regarding compliance plate requirements.

Gday...

I think the topic has wandered around a bit.

I believe what Colin was trying to convey is that to determine the ACTUAL Towball Mass (weight) one needs to place one's van across the weighbridge.

On the weighbridge,

• determine what the GTM weight (axle load) of the van is;
• determine what the ATM weight (all up weight) of the van is;
• THEN deduct the GTM weight from the ATM weight to arrive at the ACTUAL towball mass (weight).

One should also determine the 'tolerance' of the weighbridge as sometimes these have a 'tolerance' of 20Kg which means the answer to the above may mean the ACTUAL towball is + or - 20Kg.

It is invalid to read the GTM and ATM ratings from the compliance plate and apply the formula to those numbers - this will NOT determine the ACTUAL towball mass (weight) of the loaded van.

Of course, one could purchase one of those towball weight scales ... but from anecdotal evidence, their accuracy is somewhat lacking.

Of course, after determining the ACTUAL weights on the weighbridge, one should refer those numbers for GTM and ATM to the 'rating' stamped on the compliance plate to ensure that the van is UNDER (or at worst right on) those stated ratings. If so, then the van is legally compliant.

Cheers - John

-- Edited by rockylizard on Saturday 24th of February 2018 09:52:25 AM

Brenda and Alan wrote:

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I"m sorry Colin but you are wrong with regard ATM and GTM. ATM is the plated maximum all up weight of the van on its own. GTM  is NOT a fixed mas but is the weight on the axles of the van when coupled to the tow vehicle. Therefore it is always (ATM - GTM equals towball mass). GTM is a variable according to van loading and is not a FIXED mass by the manufacturer. ATM on the other hand is a fixed mass by the manufacturer and is not alterable. Hence tow ball mass varies likewise with van loading. `

Alan

-- Edited by Brenda and Alan on Friday 23rd of February 2018 12:18:46 AM

-- Edited by Brenda and Alan on Friday 23rd of February 2018 12:19:28 AM

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Hi Alan.....My compliance plate shows ATM as well as GTM.It also shows the maximum permitted load on my

vans axle group,which is exactly the same as the GTM.I do not disagree that GTM is a variable,but on my van

it is listed,and is the same figure as the factorys maximum axle loading figure.

Coincidentally(?) my ATM is 10% more than my maximum GTM figure.       

                                                                                                    Cheers 

Gundog wrote:

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This the biggest can of worms wriggling all over the place. ATM is the maximum all up weight of an unhitched trailer. Nothing more no if buts or maybes. GTM is the hitched weight of the trailer when connected to the towing vehicle end of story. The only other weights that matter are :- GVM - gross vehicle mass the maximum weight the vehicle can weigh. GCM - gross combined mass the maximum weight of the tow vehicle and trailer. Towball weight is only regulated by the towbar manufactures ID plate affixed to the towbar, The towing capacity of a vehicle is regulated by the manufacture of the vehicle, generally this is clearly stated in the owners manual, along with maximum axle weights. The opening post made mention and used their name as an authority on the subject, that being the Caravan Council of Australia, such a name does conjure the illusion that the organization is held in high esteem. Attempts to find out the workings of this council leads to it being a registered business name of an individuals family trust, which has another registered business name which identifies the individual as a consulting engineer. So using the Caravan Council of Australia as an authoritve organization is a sham, its just another person with an opinion.

 

Gundog,

I think that's a little bit harsh.

The CCA offers some great advice to experienced and prospective caravaners, even to the point of offering free legal advice.

It is a not for profit service as no fees are requested to access their services. Colin Young puts a lot of effort and time into running it.

Colin, who is ex RVMAA is an engineer and like everybody else on this and other forums he has his professional opinion on various matters to which he is entitled. Some of us may not agree with his views and express opinions of our own to which we are equally entitled.

This in no way reflects on the CCA and the services it provides and I would certainly not label it a sham.

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yobarr wrote:

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Gundog wrote:

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This the biggest can of worms wriggling all over the place. ATM is the maximum all up weight of an unhitched trailer. Nothing more no if buts or maybes. GTM is the hitched weight of the trailer when connected to the towing vehicle end of story. The only other weights that matter are :- GVM - gross vehicle mass the maximum weight the vehicle can weigh. GCM - gross combined mass the maximum weight of the tow vehicle and trailer. Towball weight is only regulated by the towbar manufactures ID plate affixed to the towbar, The towing capacity of a vehicle is regulated by the manufacture of the vehicle, generally this is clearly stated in the owners manual, along with maximum axle weights. The opening post made mention and used their name as an authority on the subject, that being the Caravan Council of Australia, such a name does conjure the illusion that the organization is held in high esteem. Attempts to find out the workings of this council leads to it being a registered business name of an individuals family trust, which has another registered business name which identifies the individual as a consulting engineer. So using the Caravan Council of Australia as an authoritve organization is a sham, its just another person with an opinion.

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Hi Graham....Even the most challenged amongst our readers should be able to comprehend your clear,concise and.           accurate description of the various weights,and how they are applied.Thanks! And I applaud you for your efforts in tracking             down and exposing the apparent rort that is the Caravan Council of Australia. Something didnt sit quite right there,and you have revealed the truth! Thankyou.    Cheers.

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 And what sinister truth might that be?

What possible motive might Colin have for "rorting" anybody?

The CCA is an independent body with no connection whatever to any official industry body.

rockylizard wrote:

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Gday...

cheers - John

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 Either they were uneducated, uninformed and negative posts or you have a point.

What do you think? 

-- Edited by montie on Saturday 24th of February 2018 07:59:42 PM