Towing, Why The Big Numbers Aren’t The Whole Story

[motorculture]

Well done for addressing this most overlooked issue which is also the most misunderstood! Is there any compensation for the amount of leverage that tow ball loads apply ie 300kg tow ball load is equivalent to 400kg payload in the tray?

Thanks Old Jack. No, the payload in the tray is independent of the towball download.

Pity the front axle load limit on the new Triton is only 1260kg (same as previous models) I know the engine is lighter but by how much? Can a steel winch bar, winch, second battery and 2 adults sit in the front and be under the front axle load limit?

cheers, old Jack.

The engine weight doesn't really come into the equation of this as it's a completely new car with different specs and tow ratings. You're right on the front axle mass being 1260kg and the best thing to do would be to put this over a weigh bridge. The weight in the car is spread across the 2 axles so it really depends how you load the car to determine if this is acceptable.

[2bad4u]

Just have to love the law, not. Ok hunting out class C and it only mentions GVM of 4.5 tonnes but total CGM must be no more than maximum allowed by the manufacturer. So in my case 2.8 plus 3 giving 5.8 tonne CGM, providing my compliance plate allows this but as tow bar down weight is a factor of vehicle GVM then Total 5.5 tonne given caravan 300 kg down weight. As discussed this is theory in practice two tonne caravan likely the practical limit for the 2.5HP given caravans collect weight.

Checked out the GM Chevy monster. Chuckled as GVM is 4536 so anyone with a class C please visit the local police station and hand yourself in Towing capacity is reported up to 9.8 tonne but that varies between web sites and GCM is around 11 tonne according to the importers. So if I drive a five tonne GVM truck I am off to court only to be overtaken by a 11 tonne rig if you ignore the extra 36 kilograms

Main thing is unless I am misreading as long as I stick below GCM, which I need to check for the PC Challenger, I am legal. Ok safety and practicality I agree might not be as so certain. Must borrow a big caravan to see how this works in the real world but that requires an electronic braking system to be installed. What was my GVM again

Your sums are wrong in that the 300kg doesn't disappear. If your car weighs 2.8t and caravan 3.0t (ATM) then your GCM would be 5.8t. This is total weight not axle weights. If you were to weight the car and caravan when hooked up your weights would be 3.1t car and 2.7t caravan (the 300kg is now on the car) but your GCM is still 5.8t.

As for C class and 4.5t that retaliates to the vehicle only. So you could buy a Dodge, GMC, etc that has a GVM of 4.5t and it's rated to tow 9.0t, you could legally drive a 13.5t combination on a C class licence, if that is the rated GCM of the vehicle. In your example of 11.0t GCM then you could load the vehicle to 4.5t (including ball weight) and only tow a van of 6.5t + ball weight (not the claimed 9.8t).

[Ent]

Your sums are wrong in that the 300kg doesn't disappear. If your car weighs 2.8t and caravan 3.0t (ATM) then your GCM would be 5.8t. This is total weight not axle weights. If you were to weight the car and caravan when hooked up your weights would be 3.1t car and 2.7t caravan (the 300kg is now on the car) but your GCM is still 5.8t.

As for C class and 4.5t that retaliates to the vehicle only. So you could buy a Dodge, GMC, etc that has a GVM of 4.5t and it's rated to tow 9.0t, you could legally drive a 13.5t combination on a C class licence, if that is the rated GCM of the vehicle. In your example of 11.0t GCM then you could load the vehicle to 4.5t (including ball weight) and only tow a van of 6.5t + ball weight (not the claimed 9.8t).

The sums make an assumption that the downward ball weight forms part of the tow vehicles GMV. So while you are correct that the down weight shifts the load from the carvan to the car, I can not exceed the car's GVM, so unless I can shift the 300kgs out of the car to carvan then my effective GCM has to go downward. If I can shift the weight then I agree that the GCM woul be the same, providing I do not exceed the three tonne caravan limit for my car.

The Chev is interesting as the GCM comes from the importers website but a review claims 9.8 tonnes. Rather a rare vehicle but I know of a person that has three if not four for heavy duty towing. From memory he struck a problem that a trailer's GVM can only be so much and was brawling with the registration body with an unknown outcome. I still doubt the logic of fining a C class driver in a 5 tonne GVM truck versus a 11 tonne Chevy fifth-wheeler combination been ok, but that appears to be the law.

On safety never heard of any one in Tassie been pulled up but a few reports over the years from coronal inquests with charges leveled against drivers. The full strangeness of the law was my XR6 Turbo. Its maximum towing was 1.6 tonne while the six and V8 versions were 2.2 tonne. The reason was the torque curve of the turbo was very hard on the Falcon's driveline. The manual was limited to 1.1 tonne for the same reason. They all could be fitted with the same tow bar but it was still illegal to tow above the vehicles restriction even though the reasons are to protect the driveline, not any other safety reason. I believe a few other cars have had their Aussie towing restricted due to heat concerns, which in Tassie is not an issue, but as the Registration authority told a friend with one, he could only tow what the Australian compliance plate allowed, not what the English one could.

Interesting, more than a few people are claiming that 2.5-3.0 tonne class caravans should only towed by such vehicles as the Chevy, and point out a Landcrusier 200 with 300kg ball weight caravan is very easily stretched past its GVM.

O'well, as long as you understand the law then legally you will be ok. Not so sure on the safety aspect of some combinations, plus if they are practical. I am rather old school in my belief that a car should never tow anything heavier than it, but that was from the days of indifferent brakes. I would image a well setup trailer braking system has changed this. Hence, reading up on them.

Still a lot for me to learn on this issue of towing and might be better compromise on luxury for a more practical solution.

[craka]

Just obn that statement of belief of a car shouldn't tow anything heavier than it's own mass. Has anyone noticed that prime movers weigh a lot less than their loaded trailer mass? They of course have trailer brakes.

Any car trailer over 750kg also needs to have trailer brakes.

[nj swb]

Just obn that statement of belief of a car shouldn't tow anything heavier than it's own mass. Has anyone noticed that prime movers weigh a lot less than their loaded trailer mass? They of course have trailer brakes.

Any car trailer over 750kg also needs to have trailer brakes.

Also complete different dynamics, in the way that the mass of the trailer affects the prime mover. For instance:

• much more of the trailer weight is on the prime mover rear wheels
• the "pivot point" is forward of the rear wheels, not behind - no "tail wagging the dog"
• the centre of gravity of the trailer is between the rear wheels and the pivot point, not somewhere near the trailer wheels i.e. no "pendulum" effect is possible.

There's a lot more to towing than simply weight / mass.