Thread: Tow ball weight

Originally Posted by Dougal

Nope.
But I can guarantee you we have both far more corners and far more tourists in camper vans ambling through them.

The worst part is a 15km/h corner (steep and tight) with a 44 seat tourist bus coming the other way.
Thankfully we don't have many 15 km/h corners, but plenty of 35's.

I'd say you've got us there, coupla 30odd kph corners on elephant pass on the east coast, but I'm not here for a "who has the most dangerous roads" ****ing comp....... As we have seen, sometimes the straightest, nothing bit of road can be the scene of an accident.

Driving to your, the vehicles and the roads abilities and conditions is what it's all about, the old man taught me to drive as if there is a stone wall around every blind corner, and while you still may hit it, at least be prepared to start to stop, lessen the impact as it were. Cars driving slower than the posted limit can be a hazard, as is driving to fast so, well I don't know what the answer is apart from whats written above. It's going to be one of those ongoing discussions for quite some time i suppose.

A driving instructor once said to me (during a similar discussion), "safer roads, safer cars, stricter laws and implementing them all cost money, but a change in attitude is free".

Sorta stuck with me, especially as at the time I had just become a dad for the first time.

Who cares which country has the most corners and at what speed we we should drive at as long it is appropriate to the conditions - can we get back to tow ball weight.

The 10% rule is in fact not the optimum amount but the max weight - the optimum amount is 5% - up to max of 10%.

As the 150kg TBW is specified by the manufacturer what sort of changes would need to be made to the vehicle to allow an engineer to sign off on an increase?

Also you need to be aware that sometimes the tow bar manufacturer also stipulates a TBW and then the lower of the tow bar or manufacturer's TBW applies.

The very first discos had a tbw of 120kg that was soon increased for all D1s to 150kg - unfortunately the tow bar I bought (before I new all of this) had a plated TBW of 120kg - so make sure the plate on the tow bar is equal to or greater that the vehicle TBW.

Garry

Originally Posted by garrycol

The 10% rule is in fact not the optimum amount but the max weight - the optimum amount is 5% - up to max of 10%.

It's not a rule at all, only a guideline which applies to a small percentage of towed trailers in a certain weight range.

Originally Posted by Dougal

It's not a rule at all, only a guideline which applies to a small percentage of towed trailers in a certain weight range.

Yes, how does this apply to single, double and tri axle trailers? Why do we need towball weight at all? I would have thought that the trailer should be able to carry it's weight on its wheels not on the towball of the towing vehicle. If you tow something to the limit of 3500kg going by the guidelines 350kg or 175 kg are going to be on the ball, I am sure that would not pass the "if you can't lift it it is too heavy rule"

Originally Posted by Dougal

It's not a rule at all, only a guideline which applies to a small percentage of towed trailers in a certain weight range.

No you are correct - it is not a rule defined by law but a rule that is accepted by most people in the know - hence a guideline.

Originally Posted by garrycol

Who cares which country has the most corners and at what speed we we should drive at as long it is appropriate to the conditions - can we get back to tow ball weight.

The 10% rule is in fact not the optimum amount but the max weight - the optimum amount is 5% - up to max of 10%.

As the 150kg TBW is specified by the manufacturer what sort of changes would need to be made to the vehicle to allow an engineer to sign off on an increase?

Also you need to be aware that sometimes the tow bar manufacturer also stipulates a TBW and then the lower of the tow bar or manufacturer's TBW applies.

The very first discos had a tbw of 120kg that was soon increased for all D1s to 150kg - unfortunately the tow bar I bought (before I new all of this) had a plated TBW of 120kg - so make sure the plate on the tow bar is equal to or greater that the vehicle TBW.

Garry

Soz for the off topic garry, got swept up in it all.

When some one goes for a GVM upgrade, is the suspension all that gets considered or are other factors at play? Do they take into consideration where on the truck this new found mass is to be located?

I suppose a rough example is if bloke "A" has no accessories on his truck and bloke "B" has the entire ARB catalog attached, then bloke "A" could load the extra GVM entirely in the boot, there by all the load is now over the rear, similar to having increased weight over the ball?

The reason I ask is that if springs are all that is needed to increase the total carrying weight of your truck, then maybe thats all that is needed for this instance, if a gingerbeer would include it on the modification plate that is?

oh, and your hitch is rated for it of course.

Originally Posted by pando

Soz for the off topic garry, got swept up in it all.

When some one goes for a GVM upgrade, is the suspension all that gets considered or are other factors at play? Do they take into consideration where on the truck this new found mass is to be located?

I suppose a rough example is if bloke "A" has no accessories on his truck and bloke "B" has the entire ARB catalog attached, then bloke "A" could load the extra GVM entirely in the boot, there by all the load is now over the rear, similar to having increased weight over the ball?

The reason I ask is that if springs are all that is needed to increase the total carrying weight of your truck, then maybe thats all that is needed for this instance, if a gingerbeer would include it on the modification plate that is?

oh, and your hitch is rated for it of course.

GVM usually includes maximum axle weights, these determine how the weight can be spread front/rear.
Any extra weight added to the vehicle (tanks, accessories, passengers etc) reduce the amount that can be carried as cargo.

I don't consider springs as a way to increase the GVM of a vehicle, only a way to make it more suitable at the max GVM.

The 5%,10% etc rules far from being followed by "people in the know" are wives tales handed out to people who don't know.
For example, tandem and triple axled trailers don't suffer from sway like single axles do and don't need significant towball weight. Then we have trailers with a dolly under the front, the only towball weight becomes a proportion of the draw-bar weight. Nowhere near the 5-10% that is often repeated regardless of trailer or vehicle type.

OK, my two bob's worth time...

ECE-55 states that the maximum permissible towball download is 10% of the towed mass or 1000kg, whichever is the lesser. That's from memory, not verbatim but the figures are correct. I can't comment on the current ADR as I haven't reviewed it recently. Note that Australia will be adopting the ECE reg soon as an ADR, so it will come into effect at that time.

Putting 350kg onto the towball of a Disco will potentially not end well. I really wouldn't recommend it, plus it exceeds the manufacturers recommendations, which means you're outside of that legal security blanket as well. It would likely overload the rear axle if you're at close to GVM, with the increased wear and much higher risks of failures that entails. Any weight put on the towball is also magnified onto the rear axle due to the leverage effect of the towbar cantilevered out the back.

(Un?)common sense should prevail here, and some thought given to weight transfers under dynamic loadings (cornering, acceleration and especially braking). Braking hard with a loaded horse float hitched up is an "interesting" experience and teaches you much about Mr Newtons Laws... Think of how hard it is to maneuver a loaded wheel barrow at walking pace. Multiply that by 200-300 times in weight and 30 times in speed, and then make the contents of the barrow move about randomly... Hmmmm...