Tow ball Weight

[macca]

I have done a search on this site for this subject, but have been unable to find any information.

I am in the process of looking at buying a new car/4wd.

I have noticed amongst the specification from alot of the manufacturers, the tow ball down weight rating.

I have a 4.5 m aluminium boat, what would be the likely towball down weight from this boat/trailer?

Or is there a simple method I can use to work it out?

Thanks

Macca

[drb]

put the jockey wheel on a set of scales. If it needs to be adjusted you have to move the axle or the position of the boat on the trailer backwards or forwards to suit. Normally about 50 to 100 kgs for comfortable towing I think.

[MTpockets]

Its best to see what your towbar and ball weight recomendations say on the towbar complience plate. If it says it is rated at say 90 kgs, then use a set of bathroom scales with a block of wood (tared off) sitting on the scales then place the tow hitch on it at the same height as your towbar. That is how to acurately work it out. Then as mentioned above move the boat forward or back depending on its weight displacement. Make sure your boat is fully loaded with all your gear as if you were ready to go fishing before test is done.

cheers
Les

[NQCairns]

I had a bugger of a time doing this in the past, I found that a flat stable surface to place the scale on and then a piece of wood like mentioned by MT that spreads the load over the scale surface worked well and was repeatable, Personally I like it a bit heavey than a bit light still within specs to calm the rear of the car. Although I doubt you will really need to be pedantic with a 4.5 tinney unless it is quite a small tow vehicle.
I have worked on around 7 to 10% of total weight and yet to have a problem that I noticed. The real test is the first tow. Slightly higher in the range gives a better tow in my opinion.nq

[Gorilla_in_Manila]

I was always told ball weight should be 10% of the tow weight, and caravan / trailer manufacturers will set it up like this.
Beside the various methods of getting a set of scales under your jockey wheel (which will give you slightly less than actual ball weight), there is a specific gizmo for measuring ball weight. It basically just a steel post & base plate with a ball mounted under a heavy duty spring scale. Check with your local caravan or trailer manufacturers and they probably have one that you could use for a small fee.
Cheers
Jeff

[gofishin]

Macca, generally 7 - 10% of ATM, but this figure is limited by the smaller of:
the vehicle's maximum towbar/ball down-weight, or
towbar manufacture's towball weight (which can be much lighter than above if it is a cheapie

depending on boat type/brand/model and trailer build duty, the ATM may be between 700 - 1000kg, so a towball down-weight of somewhere b/w 50 - 100kg.

remenber, smaller amounts may mean the boat/trailer rocks back & skeg hits ground when climbing up over the transom! so 100 will be better than 50kg.

[mini696]

As stated above, ensure your boat is "As Towed" because you'll be suprised how much difference taking a battery, fueltank or electric motor out of the back can affect the hitch weight.

Can someone explain to me what effects having a heavier/lighter hitch weight will do to the handling of the trailer-car combo??

[aussiebasser]

If your hitch weight is too light, the trailer will tend to fishtail, as it will lift the weight off the rear wheels of the towing vehicle. This is extremely dangerous, and the cause of most trailer jack-knifes.
Too much weight can over stress the tow bar on the towing vehicle causing a breakage, or it can cause the towing vehicle suspension to continually bottom out, causing undue stress on the draw bar of the trailer.

[mini696]

Thanks Aussiebasser.

[macca]

Thanks for all your replies.

I tried out the method last night.

My fully laden 4.45 Hornet on the trailer has a down weight of 110 kg and the gross maximum weight for the trailer is 1000kg.

So the 10 percent theory is pretty close.

Most 4wd will have a max down weight of 130 kg after that apparently you need a weight distributing hitch.

Cheers

Macca

[Gorilla_in_Manila]

Macca,
Land cruisers are rated at 350kg ball weight straight out of the shop. Patrols were 250kg (they might have increased it by now, not sure).
My dad had to upgrade his patrol towbar and get it certified, to tow his 3T bushtracker caravan which had 10% or 300kg ball weight. No real drama getting it certified, think it just needed stronger attachment bolts and of course the heavier bar. No special hitch required.
Cheers
Jeff

[Kerry]

....Land cruisers are rated at 350kg ball weight straight out of the shop. Patrols were 250kg (they might have increased it by now, not sure)....

Most of the Patrols were/are 200kg max downball weight BUT one must relate all this to the individual vehicle as the vehicle manufacturer's specifications have the final say as it's not what the towbar can be designed to tow/carry BUT what the vehicle is designed to carry.

It can all get complicated but in the case of the Patrols the spec is 200kg at Loaded Vehicle Mass so if one is running the vehicle at or near max GVM then 200 kg is it, no ifs or buts that's what the "vehicle manufacturer" sepcificies.

However one can increase the tow ball downweight if one decreases the loaded vehicle mass. So in the case of the Patrol if one reduces the GVM by 290kg (leave the dog, the mother in law and the beer at home #:D) then the toball download can be 350kg.

Really it all gets quite complicated and normally not just a simple case of ball downweight X.

Also if the transport guys really want to get picky then not only could they take into account not only the actual towball down weight but also the actual weight on the rear axle, the front axle weight (as spec's by the manufacturer) and a maze of other things that really get picky but are all still ticketable #:-X.

And if people continue to exceed towing limits and keep having the accidents that basically have lead to the current crack down then things will probably get cracked down even more.

Cheers, Kerry.
#

[Gorilla_in_Manila]

Kerry,
Yeah, Sorry, I'm wrong again ::), 200kg (- 350kg dependant on vehicle load) for the patrol.
Couldn't for the life of me find a direct nissan spec, but found a review site that gives the towball weight as 200 - 350kg, dependant on vehicle load.
I presume when my old man got the Dept transport cert, it must have stated a requirement to reduce the load in the vehicle.


Back to the original ball weight question:

Heres a link to an article for general towing considerations.
http://www.4wdaustralia.com.au/Vehicle/Caravans/ChoosingandSettingUpaTowVehicle.asp

Note down the bottom of the page, it has a method for calculating ball weight.
Drive your loaded trailer on a weighbridge; disconnect and weigh without car.
Reconnect and drive vehicle off so just trailer wheels remain on weigh bridge.
Difference between the two weights is tow ball weight.

Cheers
Jeff