Optimal weight on a tow-ball when towing a trailer.

The apparent “rule of thumb” for the weight of a trailer (or caravan etc) on the 4wd’s tow-ball appears to be “10% of the caravan’s weight”.

Is this an engineering “requirement” or, more likely, that the weight on the tow-ball should not exceed 10% of the towed weight.

I would have thought that the optimal solution would be zero weight on the tow-ball, ie the trailer was perfectly balanced on its wheels – but clearly this would be virtually impossible to achieve.

Can anybody please enlighten me as to this matter?

With thanks,
DB

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Reply By: Best Off Road - Friday, Apr 03, 2009 at 07:42

Friday, Apr 03, 2009 at 07:42
DB,

Don't ask me to explain the engineering reasons, but with little or no downball weight a Caravan will sway like a pig. I know from experience.

10% is a definite requirement for safe and stable towing. I prefer a bit more.

Cheers,

Jim.

AnswerID: 357780

Follow Up By: Member - Paul Mac (VIC) - Friday, Apr 03, 2009 at 07:49

Friday, Apr 03, 2009 at 07:49
hahaha Jim,

How does a pig sway ?

Cheers
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FollowupID: 625890

Follow Up By: Welldone WA - Friday, Apr 03, 2009 at 21:26

Friday, Apr 03, 2009 at 21:26
I find 25kg on the ball is the ideal towing weight for my 1500kg camper trailer ,10kg lighter and it starts to dance . If I followed the 10% rule then I'd have to have 150kg on the ball,which IMHO is way too heavy. At 25 kg it makes it easy to unhitch and move around and I can load the back of the ute with another 125kg of essential camping/fishing gear.
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FollowupID: 626030

Reply By: Member No 1- Friday, Apr 03, 2009 at 07:51

Friday, Apr 03, 2009 at 07:51
try this

it might help explain it
AnswerID: 357781

Follow Up By: Member - Graham H (QLD) - Friday, Apr 03, 2009 at 09:34

Friday, Apr 03, 2009 at 09:34
That was a very interesting site BUT.

In the demo they use at shows it seems they have the axle too far forward which accentuates the problem of snaking.

Here we mostly have the axles placed more than halfway back on our tandem vans anyway and this goes some way to stopping this.
Also that type of van runs a much lower ball weight than do we.

In fact in the demo it would have no ball weight at all as the rear weigh was larger than the front one and was further from the axle so if you unhooked that in reality it would sit on its bum.

However it will answer the posters question.



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FollowupID: 625909

Reply By:- Friday, Apr 03, 2009 at 08:02

Friday, Apr 03, 2009 at 08:02
Hi DB
I am not sure that this is a requirement but it could differ from state to state i am, building a trailer in Q and i would have to reread the info but i think that the fulcrum point(the center point between the wheels if tandem or the axle location of a single axle ) needs to be no less than 50mm(i think) forward of the center of the trailer load area.
You are able to get this info from the dept road and transport, up here it is a 35 page study!!
But getting back to the weight on the tow ball, the more weight that you apply to the tow bar the greater traction you have and if you have a blow out etc. the trailer or caravan will be less inclined to be dragging the rear of the tow vehicle around.
You just have to make sure that the down weight on the cars tow ball is not exceeded.

Mattie
AnswerID: 357782

Reply By: DIO - Friday, Apr 03, 2009 at 08:58

Friday, Apr 03, 2009 at 08:58
Be guided by the manufacturer - that's what the authorities will refer to in the event of Insurance claim etc.
Check the Owner's Handbook for specifics on towing and tow ball weisght etc.
AnswerID: 357800

Reply By: ozjohn0 - Friday, Apr 03, 2009 at 09:04

Friday, Apr 03, 2009 at 09:04
Like others I have no less than 10% of the Gross Trailer Weight on the ball. It's the recommended industry standard and assist is smooth safe towing.
Mattie.
Go to this site for your trailer building requirements.
http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/vsb1
You'll note that the there is a 60/40 Rule on axle placement.
At least 60% of the trailer must be in front of the centre line of the axle(s) and no more than 40% of the trailer behind.
The only thing about these specs that has changed is the 50mm Ball Coupling Height. SHOWS 350 - 420, but NOW: 350 - 460mm.
ozjohn.
AnswerID: 357801

Reply By: Member - Teege (NSW) - Friday, Apr 03, 2009 at 09:06

Friday, Apr 03, 2009 at 09:06
Dicky
This is a very misunderstood situation. Have a read of this coroner's report. It goes into the question of zero downweight at some length.findings

teege
AnswerID: 357802

Follow Up By: Member - Teege (NSW) - Friday, Apr 03, 2009 at 09:10

Friday, Apr 03, 2009 at 09:10
I'm not sure that link is working try copy and paste this :
http://www.courts.sa.gov.au/courts/coroner/findings/findings_2006/jong.finding.htm

teege
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FollowupID: 625899

Follow Up By: Member - Mark E (VIC) - Friday, Apr 03, 2009 at 09:26

Friday, Apr 03, 2009 at 09:26
It would appear obvious even to a realatively untrained eye that the caravan is poorly designed......... just shows "caveat emptor"..

Cheers,

Mark
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FollowupID: 625907

Reply By: Rangiephil - Friday, Apr 03, 2009 at 13:32

Friday, Apr 03, 2009 at 13:32
Funny AFAIK the 10% rule is only in The USA and Australia.

In europe they have much lighter recommended tow ball weights.

I do not recall seeing reports of mass snakings.

IMHO some of the towball weights in OZ are ridiculous , like 150KG for a camper trailer.

Regards Philip A

AnswerID: 357846

Reply By: Member - DickyBeach - Friday, Apr 03, 2009 at 15:23

Friday, Apr 03, 2009 at 15:23
Thank you one and all, as others have many times remarked on this site it's amazing the collective wisdom that's available to tap.

It's 6am where I am these days (Swizterland) and when my eyelids are properly open I'll explore the various sites provided.

Cheers,
DB
AnswerID: 357866

Reply By: ozjohn0 - Friday, Apr 03, 2009 at 15:36

Friday, Apr 03, 2009 at 15:36
The Europeans also tow with much smaller vehicles that can't handle a decent ball weight and the vans are fitted with Anti friction (Anti Sway ) couplings to stop the snaking.
With their roads and our etc there is absolutely no comparision.
Try towing their light weight vans around on our bush roads and see what happens. Ouch!!!
Many years of towing by many hundreds of thousands of vanners in this country have confirmed that the 10% recommendation is a good sound safety feature. As is the use of a WDH which again the Europeans don't use.
ozjohn.
AnswerID: 357869

Follow Up By: Member - DickyBeach - Friday, Apr 03, 2009 at 15:44

Friday, Apr 03, 2009 at 15:44
Johno (and others),
I should have added that we're returning to Godzone later this year and my query most certainly related to Oz conditions.

And, yes, there is a HUGE difference in roads - I cringe when I think of our Australian "highways" and freeways etc [and I actually saw a dirt road the other day over here :) ].

Cheers
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FollowupID: 625963

Follow Up By: Member - Graham H (QLD) - Friday, Apr 03, 2009 at 17:46

Friday, Apr 03, 2009 at 17:46
From the Eurorean vans I have seen they mostly use a Winterhoff coupling which actually grips the towball and helps prevent sway.

Also our vans are much higher off the ground than them and are a lot heavier and so are inherently less stable for a start.
If you dont think a semi can affect you think again.

For a start when towing the van I have had two rear spare wheel covers literally sucked off the rear of the cruiser by passing semis.(Now I tie them on)

Have noticed on the Hume in the last few days that you can actually feel them as they get level with the van.

They seem to have a "Bow Wave"that pushes the van to the left then as they fully pass you it sucks you to the right.

Inexperienced drivers could be correcting the first and get caught by the second and get into trouble rather quickly.
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FollowupID: 625996

Reply By: ozjohn0 - Friday, Apr 03, 2009 at 15:43

Friday, Apr 03, 2009 at 15:43
It would appear obvious even to a realatively untrained eye that the caravan is poorly designed.........

I find that statement hard to fathom.
How can YOU tell it's poorly designed?
What's the inside layout etc. How is the weight distributed?
I've been in the game for quite awhile and I would have a clew unless I had a chance to look over the van.
Unfortunately the police and others in this incident didn't do their job right and we'll never know what the true facts were.
ozjohn.
AnswerID: 357871

Follow Up By: Member - Graham H (QLD) - Friday, Apr 03, 2009 at 17:36

Friday, Apr 03, 2009 at 17:36
Well firstly how many vans do you see that dont need a jockey wheel to keep the front off the ground.
Its plainly obvious that it appears to be rear heavy otherwise as was said in the enquiry it would not sit level as it does empty.
Even a backyard trailer does not do that.

Maybe he did load it to give it a ballweight but maybe he didnt.
Maybe he didnt have a WDH either as that would have helped steady it.
Probably thought he didnt need it due to the bad weight distribution.

As well as all that the cops didnt weigh it didnt check the loading couldnt remember where the jockey wheel was.

If it was still on the A frame he needed his head read. Fastest way to bottom out and head off road unintentionally.

Appears to be a disaster waiting to happen which it ultimately did.
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FollowupID: 625995

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