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Post by Old Techo on Jul 21, 2023 15:41:36 GMT 10
An old mate asked me for an opinion between a Prado and a Mux.
I explained about deceptive marketing.
Example current Prado:
GVM = 2990kg
Payload = 715kg
Braked towing capacity = 3000kg
GCM = 5990kg
Thus a fully loaded Prado plus a 3000kg trailer = 5990kg = the GCM
Example current Mux:
GVM = 2800kg
Payload = 620kg
Braked towing capacity = 3500kg
GCM = 5900kg
Thus a fully loaded Mux plus a 3500kg trailer = 6300kg and exceeds the GCM by 400kg
To legally tow the claimed 3500kg the Mux payload would have to be no more than 220kg
So maybe only a driver and passenger plus fuel.
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Post by spaceland on Jul 21, 2023 18:14:35 GMT 10
Example current Mux:
GVM = 2800kg
Payload = 620kg
Braked towing capacity = 3500kg
GCM = 5900kg
Thus a fully loaded Mux plus a 3500kg trailer = 6300kg and exceeds the GCM by 400kg
To legally tow the claimed 3500kg the Mux payload would have to be no more than 220kg
So maybe only a driver and passenger plus fuel. First let us go back to basics and look at the definition of GCM. From the latest issue of Vehicle Standard (Australian Design Rule – Definitions and Vehicle Categories) 2005, Compilation: 13 (up to and including Vehicle Standard (Australian Design Rule) Amendment Instrument 2022 (No.1)), Compilation Date: 26/10/2022With a GCM of 5,900 kg and a tug GVM of 2,800 leaves a maximum axle loading of 3,100 kg. If you have a van weighing 3440 kg and a ball load of 10% would have a group axle weight of 3096 Kg. The 620 kg payload less the 344 kg ball weight would leave 276 kg from the total loading allowance.
Whilst your original false specification claim is still valid, the situation is not as bad as you suggested. Also note, you cannot discount the GVM of the tow vehicle to allow for a larger van to be towed. This last point is particularly important when you are using a ute which has a much larger loading allowance than a station wagon style tug.
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Post by Old Techo on Jul 22, 2023 8:27:01 GMT 10
Despite staring at it for 30 minutes last night and another 10 mins today I still can’t follow your point PD. Mind you, my 0240 start to the day has quarantined most of my neurons 
Prior to trying to explain it over the phone to my mate I’d scratched some specs on a bit of paper and they are basically what I posted here.
Over the phone I used a simplistic model of 2 masses. Mass A is the tug and mass B is the trailer but only towed by a rope. I did not want to complicate our phone chat with ball weight factors or strict definitions.
Mux advertising (specs) say mass A is good for up to 2800. It also says that mass A can pull mass B of up to 3500. It does not spell out that either mass A or B must be reduced by a total of 400 when they are linked to remain within the GCM.
So the point of my post was to declare that practice as deceptive. I suspect that other brands do the same thing.
In your example mass B is 60kg less than mine thus improving your payload.
I could guess that terms such as GCM began life in the trucking industry. The tendency to overload was driven by money.
If a caravan was a dog trailer rather than a pig/box trailer then ball weight would never be factored in.
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Post by spaceland on Jul 22, 2023 16:47:17 GMT 10
OT, You were reducing the maximum permissible weight of the tug to allow an increase in the allowable eight of the trailer. Read the definition of GCM from the standards again. In every situation where you are calculating the GCM of a rig you must use the GVM of the towing vehicle of that vehicle. If you are flat towing another vehicle with a MUX then the towed vehicle can not exceed 3,100 kg. The only way you can tow a greater weight than that is to tow a pig trailer so some of the trailer weight is supported by the tug.
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Post by Old Techo on Jul 23, 2023 14:53:23 GMT 10
Fair-enuff PD 
My aim was merely to highlight spec deception. Perhaps spec-traps for young players would be a better description?
I accept that in juggling numbers I have not used the rules correctly to demonstrate my point.
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