Ball weight... how do you calculate

Submitted: Friday, Feb 10, 2006 at 19:48
ThreadID: 30661 Views:19276 Replies:9 FollowUps:15
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As per previous post we have been looking at 80 Series Landcruisers to tow 2100kg tandem van. I am becoming confused as to towing capacity and ball weight.

Looked at an 80 series and the plate on the tow bar stated towing capacity of 3500kg but "B" equating I believe to ball weight and/or downward pressure on tow ball was only 120kg? Am I missing something, somewhere?

Everything that I have read so far suggests that the ball weight is calculated at 10% of the weight of the trailer / van being towed.

When in S.A. we heard of a number of vanners who had been checked by the "scalies" and some were booked for exceeding towing capacity (fair enough) and exceeding recommended ball weight.

Any help would be appreciated, but please KIS, keep it simple for my brain to comprehend.

Cheers

Graham and Sandy
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Reply By: Old Scalyback & denny - Friday, Feb 10, 2006 at 19:59

Friday, Feb 10, 2006 at 19:59
the ball weight and the towing capacity is normally on the tow bar and is set by the manufacturer some were readjusted as to light but i dont know where you go to find out maybe a tojo dealer hope you have more luck than i did with an early nissan the dealers were dumb oops sorry played dumb
the 2 weights you have are probably right

steve
AnswerID: 154363

Follow Up By: sandyngraham - Friday, Feb 10, 2006 at 20:22

Friday, Feb 10, 2006 at 20:22
Hi Steve,

Thanks for the info and thanks to the rest of the wise people that frequent this forum. Had a look at you rig profile, can you tell me the make, size and weight of your van.

Cheers

Graham
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Follow Up By: Old Scalyback & denny - Friday, Feb 10, 2006 at 20:53

Friday, Feb 10, 2006 at 20:53
goodday graham
the van is a paramount "delta"17'6 internal about 2t+ loaded
when looking at vans dont be fooled by the sales people and van weights and ball weights as they are all done when van is empty it all changes when tanks are filled stuff put under the bed and if the water tanks are both in front of the axle it adds a lot to the ball weight when full
have a look at the hayman reece site it gives some goood tips and also how to get the ball weight properly with house hold scales

steve
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Reply By: yota - Friday, Feb 10, 2006 at 20:08

Friday, Feb 10, 2006 at 20:08
Sit them on a scale?
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Follow Up By: Trevor R (QLD) - Friday, Feb 10, 2006 at 21:04

Friday, Feb 10, 2006 at 21:04
Easier said than done sometimes. My ball weight was in excess of 300kg and would have surely stuffed most bathroom scales. Better option is to go to caravan repairer and ask them to tell you unless you can lift the front of the van by hand, then you would be sure not to stuff a set of bathroom scales.
I personally prefer a bit of extra weight on the ball as I think the trailer tows better this way as opposed to tail heavy. So long as the vehicle is set to cope with this and you don't go stupid all should be OK.

Regards Trevor.
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Follow Up By: The Explorer - Friday, Feb 10, 2006 at 21:08

Friday, Feb 10, 2006 at 21:08
Yota - assume you mean a kitchen scale?
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Follow Up By: V8Diesel - Saturday, Feb 11, 2006 at 12:52

Saturday, Feb 11, 2006 at 12:52
Ball weight in excess of 300kg's - strewth! If mine weighed that much I'd think I'd gladly stuff anything. A man's not a wheelbarrow.

re: the kitchen scale - thanks but I think I'll politely 'pass' on the next cake you bake then:-)

Much childish giggling going on here. bbbbbwahahahahahhaha:-)))
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Reply By: Member - Norm C (QLD) - Friday, Feb 10, 2006 at 20:13

Friday, Feb 10, 2006 at 20:13
G&S, if you are trying to measure your ball weight, there are a couple pf simple ways:

1. You can buy (or borrow) a hydraulic jack with a scale on it. A lot of caravan places have them and you could probably borrow or hire one..

2. A simple 'home made' solution is using bathroom scales. If you are worried about going over the scale limit, use two. Put a piece of timber between them and rest the jockey wheel on the timber. Add together the reading of the two scales.

If using one scale, you might put a square of timber on the scale to spread the load a bit so you don't stuff it up.

As to your tow bar being rated to just 120KG, this is possible. It is almost certain that the vehicle is rated to 10% of it's tow capacity, but not all tow bars are created equal. There was a thread one here a few weeks back about it. The plate on the bar will show the rating and you are probably reading it right. You might be up for a new bar.

I'd speak to the tow bar manufacturer about it.
AnswerID: 154369

Follow Up By: Aston - Friday, Feb 10, 2006 at 20:54

Friday, Feb 10, 2006 at 20:54
You may find this helpful

Click on this and it will take you to the Hayman Reese site which will help with the way to determine the drawbar weight on the towball
vis GTW, TW capacities

link text

Cheers aston
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Follow Up By: Lone Wolf - Friday, Feb 10, 2006 at 20:56

Friday, Feb 10, 2006 at 20:56
"2. A simple 'home made' solution is using bathroom scales. If you are worried about going over the scale limit, use two. Put a piece of timber between them and rest the jockey wheel on the timber. Add together the reading of the two scales"

The Jockey Wheel will show more weight. The reading needs to be directly UNDER the ball housing.
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Follow Up By: Member - Norm C (QLD) - Friday, Feb 10, 2006 at 22:11

Friday, Feb 10, 2006 at 22:11
Hi Lone Wolf. I'm not going to claim to be an expert, but here is my understanding:

100% of the weight of the van is transmitted to the ground, no more no less. It is transmitted through any load bearing point. In this case we have 4 wheels (I think) and a jockey wheel (or tow ball if attached to the vehicle). Providing the jockey wheel is set so the van coupling is at the same hight as it would be when attached to the vehicle, the weight transmitted through the jockey wheel will be the same as transmitted through the ball to the vehicle. For the purpose intended 'near enough should be good enough' as far as hight of the ball is concerned.

Put another way. The weight on the wheels will not have changed, so the balance must be on the jockey wheel, or tow ball.

Regardless of whether the wheel is resting on the ground, one scale, 2 scales or 10 scales, the same weight must be transmitted to the ground. In this case it is via the scale(s) which will accurately measure the weight. For it not to measure accurately, the missing (or extra) weight has to get to the ground somehow. It could only be via the wheels. But how could that be so?

Happy for you to correct me with better science, but that is my understanding.

I weighed my ball weight using this method. I later was able to borrow a hydraulic jack with a weight scale. Measured weight was within 5KG in 240KG or about 2%. Close enough for my purposes.
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Follow Up By: Member - Norm C (QLD) - Friday, Feb 10, 2006 at 22:25

Friday, Feb 10, 2006 at 22:25
Check out Aston's link to the Hayman Reese web site (above). They use the same 'science' as me, but being smarter, they use one scale and a brick (rather than 2 scales). If you place the tow ball exactly half way between the scale and brick, you multiply the measured weight by 2 to get the actual weight (the other half of the weight is carried by the brick. Place it 2 thirds of the way towards to the brick, multiply by 3 etc. Using this method you could theoretically measure any weight, regardless of the capacity of the scale.
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Follow Up By: Lone Wolf - Friday, Feb 10, 2006 at 22:28

Friday, Feb 10, 2006 at 22:28
Actually Norm, that is a good call, and I had to think it through...

My reasoning, and may I please re-iterate, my own reasoning, is due to simple leverage.

If I move my trailer, and lift it with the handle, which is very close to the ball coupling, I am lifting around 27 kg.

If I do the same thing, but move my hand in towards the trailer, by about a metre ( where my jockey wheel is), I struggle. If I keep moving back, and try to lift at one of the wheels, I'm battling with 120 kg ( approx.)

Bit like pushing open a door in your house with the handle, and then doing it again at the hinge... leverage.

Anyway, it's late, and I'm splitting hairs... lol.

Cheers

Wolfie

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Follow Up By: V8 Troopie - Saturday, Feb 11, 2006 at 01:41

Saturday, Feb 11, 2006 at 01:41
I'll back you up on that one Wolfie, it is indeed the lever arm length principle that applies here.
As you say, some jockey wheels are fixed far enough back from the coupling to give a very wrong reading.
And no, you're not splitting hairs at all her.
Klaus
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Follow Up By: Member - Norm C (QLD) - Saturday, Feb 11, 2006 at 11:20

Saturday, Feb 11, 2006 at 11:20
Lone Wolf and V8, of course you are right if the jockey wheel is set well back. But this is true no matter what scale you use. A common method of measuring ball weight is to get the jockey wheel onto a weigh bridge, but leave the wheels just off.

Only way to solve the leverage effect, if it is large, is to rest the coupling on something, like a couple of bricks, then deduct the weight of the bricks. Pretty simple.
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Reply By: Max - Sydney - Friday, Feb 10, 2006 at 20:19

Friday, Feb 10, 2006 at 20:19
Graham

The rules were changed after the 80 series model run, and you can get a new rating plate for your towbar with the new values.

Mine is a Hayman Reece, and I got a form from the bloke who sold me the towbar & fitted it. I filled it out, sent it to HR, and got a new plate to weld on and a certificate to show important people in uniforms.

I had the smaller towbar, and it was upgraded to 2500 kg and 250 kg ball weight - all I need for my van. I understand the larger bar is uprated to 3500and 350 kg.

As for knowing what you have - two options. Go to a weighbridge at the start of a trip when you are loaded up, and get the total weight and the ball weight for about $25. Alternatively Maytow in SA (1300 629 869) have little scales cum jack that you can use. They ship them for $149.

As for KIS - I am an engineer and the "simple" explanations and variety of terms used confuse me. I just make sure my weight is well down from the towbar weight and the van balanced so about 10% is on the ball.

Hope that helps
Max
AnswerID: 154372

Reply By: Dazmit - Friday, Feb 10, 2006 at 20:59

Friday, Feb 10, 2006 at 20:59
Hi Graham

My understanding is that the 80 series prior to the 1996 update model were rated at 2500 kg / 250kg towball - the post update were rated at 3500kg / 350kg towball.
You prob have a older towbar and should be able to get the updated sticker to improve the 120kg towball. If you have the pre update model I don't believe you can upgrade that to a 3500 kg /350kg.

If your van weighs 2100 kg and you are free camping and will carry a few water tanks , genny etc in the van then you will quickly load more than 400kg into it.

Best thing you can do is take it to a public weighbridge. You might be surprised in that the actual weight of the van empty is greater than plated value (happens a lot of the time) and also they will measure the ball weight for you.

Cheers

Darryl
Brisbane
AnswerID: 154378

Follow Up By: Muzzgit (WA) - Sunday, Feb 12, 2006 at 02:28

Sunday, Feb 12, 2006 at 02:28
That used to be the case. Caravans were made in batches and one or two were weighed and the whole batch would be plated the same, but the are not allowed to do it anymore.

Each individual unit must have it's tare weight stamped on the plate.
(so Jayco tell me)
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FollowupID: 408465

Follow Up By: Dazmit - Monday, Feb 13, 2006 at 08:26

Monday, Feb 13, 2006 at 08:26
That may be true but do the manufacturer's use weighbridges which would be regularly calibrated or do they use their own which have probably never been check calibrated since purchase 10 years ago and could now be reading 100kg or more incorrect ???

Cheers

Darryl
Brisbane
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FollowupID: 408645

Reply By: Mulga Bill - Friday, Feb 10, 2006 at 21:42

Friday, Feb 10, 2006 at 21:42
Its a big general subject Sandy - its been covered in hoards of forums in caravan mags and elsewhere - there are some good articles here and there on the web.... a search should turn them up.
Putting the 80 aside for a moment, I think its fair to say that the vehicle manufacturers rating for towed weight and ball weight is one issue. The entirely seperate issue is what the van is doing. You need to get the car and the van matching up, as it were. If the loaded van, all up, is less than the vehicles towing max AND you arrange the van so that the weight on the hitch is inside your vehicle's ball-weight spec, you are away ! A balanced van is bad news for tracking, and therefore, safety. That's where the 10% down at the front guide comes in. The trick is keeping that 10% inside the car's spec ! It can be a real problem with some makes, but not yours - as those more familiar with the Toyotas have said, you would be way over 120g - me ? I'm stuck at 120kg with the Jack.
AnswerID: 154387

Reply By: JustyWhyalla - Friday, Feb 10, 2006 at 22:01

Friday, Feb 10, 2006 at 22:01
I would add you have three issue's rather than two!

1 - The Vehicle and what the manufacturer rating is

2 - The towbar (Sometimes people insist on a lower rated bar to save a few bucks because they only tow the 6x4 to the dump every now and again!)

3 - The van

Interesting point made earlier about trying to get information from dealers/manufacturers. I used to sell New Vehicle's and it was interesting how many times I discussed these sort of issue's with people who were looking at buying only to have them come back after going to EVERY dealer they could and getting the "best" price off of someone who has no knowledge and is not interested in what all of this type of stuff actually relates to.

So when people complain about things like that, I can't help but think as much as people complain it boils down to 1 thing to MOST people. You can sell the vehicle as cheaply as you can, know nothing, not care less about after sales service and you will still outsell the person who actually takes the time to understand all these related issue's and help's people to make the right decision for them.
AnswerID: 154389

Follow Up By: kesh - Saturday, Feb 11, 2006 at 07:44

Saturday, Feb 11, 2006 at 07:44
An interesing aside to this, is what information the manufacturer of the vehicle provides to the purchaser.
In 1997 I bought a new Toyota diesel tray back. Now this is a vehicle designed to carry loads and presumably also built to tow. But what does the owners manual say about permissable loads, trailer weights etc.?
Apart from a GVM of 3150kg., absolutely nothing.
I also have a Landrover Discovery, also bought new 1997 which in its owners manual gives max. figures for ball weight, allowable towed weights (various brake combinations), max allowable weight over front axle, rear axle and GVM. It also recommends that levelling aids should not be used.
This is the sort of information I believe all manufacturers should provide, it corresponds to the sort of questions frequently asked and relieves the sales person of that responsibility
kesh
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FollowupID: 408394

Reply By: Member - Collyn R (WA) - Saturday, Feb 11, 2006 at 13:07

Saturday, Feb 11, 2006 at 13:07
No need for two sets of bathroom scales to check ball weight. One will do.

Place one end of a plank (about a metre long) on the scales and the other end on a chunk of wood about the same height. Arrange further blocks so that the weight of the coupling (not the jockey wheel) is carried by the plank arrangement.

Lift the 'van on to the blocks as close as possible in the centre of the plank. Multiply the scale reading by two. This is close enough for most purposes.
Collyn Rivers
AnswerID: 154442

Reply By: desert - Sunday, Feb 12, 2006 at 13:12

Sunday, Feb 12, 2006 at 13:12
All this scales and calculations methods is fraught with error. Just go to a public weightbridge and drive on but leave the wheels of the van off the bridge. This is the weight of the vehicle and that portion of the van that is exerting down force on the vehicle. eg, the ball weight. Now reverse off the bridge, unhook the van and weight the vehicle by itself. Subtract weight B fro weight A answer = ball weight.
AnswerID: 154558

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