Info regards Ball Weight, please:

Submitted: Wednesday, Jul 25, 2007 at 11:55

ThreadID: 48081 Views:4872 Replies:7 FollowUps:8

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Tow Vehicle Setup

Everyone who intends to tow a caravan, or indeed any sort of trailer, needs to be aware that various tow vehicle and trailer combinations can behave in slightly different ways and certainly different

glids

G’day all,

I am after a clarification regards the effects of incorrect ball weight on a van.

I have a 16’-6” single axle van that weighs 1970 kg all up, with 1860 kg on the axle – ie there is 110 kg or 5.6% of the weight on the ball. I have a 4WD weighing over 2 tonne as tow vehicle, and I use a HR 250 kg weight distribution hitch.

I have read in many sources that the ideal weight distribution is to have 10 to 15% on the ball, with general comments about ‘better balance and control, less sway etc’ with weights in this range. I have not suffered any sway problems, but the ride has been quite ‘choppy’. The tow vehicle’s suspension has recently been upgraded and is now a good deal stiffer, but I have not yet had a chance to see if this has improved the ride when towing. However, I am concerned that my light ball weight could be a contributing factor.

It will not be easy to alter the load distribution to increase ball weight as we do not have much heavy gear at the back. I have considered replacing the 60 litre water tank with 80 L, and move it 600 mm forward (we generally run with full tank) but this will only change the load to 6.3% as most of the added weight is still nearer the axle.

I have considered bolting a block of lead right up in the apex of the A-frame, but adding 40 kg there would only change the distribution to 7.1% which seems insignificant.

I would appreciate any comments regards the above situation. In particular:
* what are the symptoms of having too little weight on the ball?
* would changing the distribution by either of the two methods above (move tank or add lead) have any real effect?
* any other

Many thanks,

glids

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Reply By: Wizard1 - Wednesday, Jul 25, 2007 at 12:15

Wednesday, Jul 25, 2007 at 12:15

The symptoms could be:

The location of the van axle causing too much weight to be to the rear.

Having too much weight too far to the rear such as spare tyres, etc. and not enough to counter that up forward.

Having your kitchen, fridge, etc to the centre or rear of the van can have an obvious effect.

Do you have a front boot? Could you fit an extra or relocate your water tank forward of the axle?

What make of van is it?

We have a forward kitchen on a single axle and our towball weight has been around 180 kg. We also have a second water tank (50 kg) rear of the axle as well as two 15 inch spares on the rear bumper and storage pipes.

But to counter all that carry a fair bit of extra weight forward on the A Frame such as a storage bin and 2 jerry cans so the chances of my towball weight being too low are slim.

You are obviously experiencing increased yawing by not having enough weight on the towball. But I suppose if it doesn't exceed the maximum for the towbar then I guess you need to distribute weight to make the towing comfortable and safe.

AnswerID: 254383

Follow Up By: glids - Thursday, Jul 26, 2007 at 09:50

Thursday, Jul 26, 2007 at 09:50

Hi, thanks for the response.
1. cannot move the axle
2. kitchen, fridge etc is in middle/slightly forward of axle
3. have spare on the rear bar and considered moving it forward of front boot, but don't really want the inconvenience of it there amongst the gas bottles etc, and cramping access to the boot
4. I'm considering an extra storage box in front of the boot. This would be handy for some items as the boot is relatively narrow. 100kg of box and bits would increase ball load to 178kg or 8.6%. This, and moving the water tank forward are my best options so far, but I'm wondering if the trouble (and cost) is worth the 3% increase in ball weight.
5. not experiencing 'yaw' (rotation on vertical axis). I believe it is 'pitching', but again, I'm not sure if increasing ball weight by 3% will fix that.

thanks anyway,
glids

FollowupID: 515573

Reply By: MEMBER - Darian (SA) - Wednesday, Jul 25, 2007 at 13:32

Wednesday, Jul 25, 2007 at 13:32

Ideally, transient factors like water and fuel loads should be close to the axle (they won't always be full) - not always practical but that's the principle I reckon. I have read a lot on this and one thing is clear - there's a lot of waffle in the industry but little is set down in hard copy - even when people die and coroners have to make findings, the whole story often stays quite muddy. You seem to be on top of the facts - working it out for yourself in effect - in law, you are on your own, anyway.
Re 10% - an 'accepted industry guideline' it seems - probably helpful too - far as I can see, in theory, IF we could have the van axle right at the back and IF we could take that extreme ball load on the vehicle, the situation would be entirely stable under normal circumstances. Bringing the axle forward and thus lightening the ballweight introduces compromise - the 10% suggestion seems to be a sensible limit on that compromise. Guess you just have to re-rig some hardware....
BTW - have you read...
Site Link

AnswerID: 254391

Follow Up By: glids - Thursday, Jul 26, 2007 at 09:52

Thursday, Jul 26, 2007 at 09:52

Thanks Darian.
The Coroner's report made interesting reading.

cheers,
glids

FollowupID: 515574

Reply By: whyallacookie - Wednesday, Jul 25, 2007 at 13:33

Wednesday, Jul 25, 2007 at 13:33

The weight distribution hitch you are using will also effect this. The 10% is an estimate before adding weight distribution hitches etc. These effectively alter the amount of effort placed on the rear wheels and move some forward

When the van is hitched up is there any noticeable difference in steering effort required? How does the vehicle sit before and after attaching the van (level, nose up, nose down)

The other area to consider is braking. Most of your braking is done by the front axle so you don't want a "floaty" front end if you need to brake (the weights involved require trailer brakes but the same issues arise)

How about placing a couple of 20l water containers in the front of the van? Or perhaps unload some of the gear from the rear of the vehicle and place it in the front of the van.

It might be worth visiting a caravan yard in your area and having a talk with them

AnswerID: 254392

Follow Up By: glids - Thursday, Jul 26, 2007 at 10:01

Thursday, Jul 26, 2007 at 10:01

Hi whyallacookie.

Vehicle sits level before attaching van, then drops back end under load. WDH levels this out fine, and no problems with steering or braking (electric with prodigy).

Unfortunately we do not have much heavy gear in the back half that can be moved forward.

I will be contacting the manufacturer to discuss the matter, and see if I can arrange a swap of 60L tank to 80L, which I would mount further forward. I think they got their sums wrong when placing the axle, but the van is a custom build and they would not have had all the weights to work with (although I gave them what I expected to be the main contributing factors such as house batteries, solar cells etc.) We did put heavier innerspring mattresses on the 2 single beds at the rear, and they may have based calculations on foam.

thanks for the comments,
glids

FollowupID: 515576

Follow Up By: whyallacookie - Thursday, Jul 26, 2007 at 10:15

Thursday, Jul 26, 2007 at 10:15

Have you tried discussing these details with the manufacturer of the weight distribution hitch (if possible) otherwise try contacting Hayman Reese they are usually very helpful.

I too have read several coroners reports and even the transcripts from several "experts" who were assisting investigations and even they can't agree quite often on this. I think the government needs to spend some money on getting some more detailed answers to this issue and making sure we all get it right.

I am no expert but I would guess the set up you are running is fine and safe WHEN using the weight distribution hitch but not without. (no doubt you always use it when towing) As the distibution hitch is transferring the weight from the rear to the front axle on the tow vehicle and effectively reducing the download effect anyway. (I can't remember who, possibly Hayman Reese, had a display set up at a caravan show with scales under the wheels of a van, both vehicle wheels and the drawbar and were showing how the weight distribution hitch moved the load. It was quite an eye opener to see the differnce it made to each axle, still don't get the exact science of how it does it but it definately does!)

FollowupID: 515580

Reply By: Member - Norm C (QLD) - Wednesday, Jul 25, 2007 at 13:36

Wednesday, Jul 25, 2007 at 13:36

My ball weight varies between 10% and 15% of trailer weight, depending on amount of fuel and water we are carrying.

From my experience, around 10% or a bit over is ideal for my set up.

Do you have the ability to turn a problem into an opportunity? Can you add another water tank towards the front of your van? Is there room and strength on the draw bar to add a couple of gerry can holders for fuel or water, or a storage box for generator, tools or other stuff. Perhaps a fold up trailer for that boat you always wanted to take with you.

Be buggered if I'd be lugging around a lump of lead. Have enough trouble fitting in the stuff we want, without adding something that does nothing.

Having said all that, I don't think you need to be too pedantic in your pursuit of 10% ball weight. I would think a 15 to 160 KG ball weight should tow pretty well for you, but only you can be the judge of that.

Perhaps you don't need the distribution hitch with the lighter ball weight?

AnswerID: 254394

Follow Up By: Member - Norm C (QLD) - Wednesday, Jul 25, 2007 at 13:38

Wednesday, Jul 25, 2007 at 13:38

150 KG to 160 KG that is.
Oh for and edit function on posts!!

FollowupID: 515443

Reply By: MEMBER - Darian (SA) - Wednesday, Jul 25, 2007 at 15:28

Wednesday, Jul 25, 2007 at 15:28

Re weight distribution hitches mention above - far as I can see (and have read) the use of such hitches only transfers load forward on the tow vehicle - no lightening at all is made to the download on the ball.

AnswerID: 254402

Follow Up By: disco1942 - Wednesday, Jul 25, 2007 at 16:46

Wednesday, Jul 25, 2007 at 16:46

Darian

You are correct. Some people think that if their ball weight is too heavy for the specifications of their tug then using WDH will make their set up legal - it does not.

PeterD
Retired radio and electronics technician

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FollowupID: 515470

Follow Up By: Member - barry F (NSW) - Wednesday, Jul 25, 2007 at 17:58

Wednesday, Jul 25, 2007 at 17:58

I agree Darian, there is heaps of waffle about ball weight & as you pointed out WDH only tsf some of the load to front axle of the tow vehicle, the actual weight on the ball remains the same. The original post indicates a to what I think is a pretty low ball weight for a reasonabley heavy van? We have a 16 foot Jayco pop top, single axle which has a tare of about 1150, by the time the wife finishes loading it we are about 1450 Kg. I have checked our ball weight with van loaded & it is usualy 145 Kg. We have the HR distribution kit & it makes things "snug", tow vehicle & van seem to be as "one" sort of thing.

FollowupID: 515484

Reply By: Member -Dodger - Wednesday, Jul 25, 2007 at 16:55

Wednesday, Jul 25, 2007 at 16:55

Often a choppy ride is due to high tyre pressures in the Van try the old 4psi or 6psi rule.

Tyre Pressures NRMA

Tyre pressures - do-it-yourself check
It is impossible to list the correct pressures for every caravan, due to variation in size, load, etc. This easy check will help you find the best pressure for your caravan tyres.
First inflate the tyres to the pressure recommended by the manufacturer of the trailer or the tyre you are using. Secondly, tow your trailer for a distance of 100 km, preferably on a highway.
Recheck the tyre pressures immediately after pulling over and compare them with the pressures you had at the start of your run. If the pressures are right, the hot readings should be 4 psi (28 kPa) higher than the cold readings.
If there is a greater than 4psi (28 kPa) difference between these pressures, the tyre temperature is too high and the pressure needs to be increased. If there is less than 4 psi (28 kPa) difference, the pressure needs to be lowered.
Large 4WD tyres will have a differential of 6 psi (42 kPa).
Be sure to use the same accurate gauge for both readings.
This may help.

I used to have a handle on life, but it broke.

Cheers Dodg.

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AnswerID: 254414

Follow Up By: glids - Thursday, Jul 26, 2007 at 10:12

Thursday, Jul 26, 2007 at 10:12

Hi Dodger, and many thanks for the tyre link. I will read that in more detail later.

I run Dunlop Roadgripper tyres in P235/75R15 108S configuration, and generally run at between 50 and 55 psi.

I sent all details to Dunlop (twice) and requested their recommendation regards pressure, but never got a reply.

Next trip I will do the pressure test after 100k's and see how they look.

cheers,
glids

FollowupID: 515579

Reply By: disco1942 - Wednesday, Jul 25, 2007 at 17:05

Wednesday, Jul 25, 2007 at 17:05

Glids

You are correct in your deductions that shifting the water tank will not change the ball weight by much. Where you will gain in stability is you will have a heavy weight on or forward of the centre of gravity and this will have a positive effect on pitching and yawing where locating it behind the C of G will have a negative effect and make these forces worse.

In reply 3 mention is made of locating disposable loads well forward to establish a 10% ball load. This is of not much use as when you dispose of these liquids you are in trouble again. In Reply 4 reference is made of the changing ball weight changing as the load fuel and water changes – In this case it is OK as he has a minimum of 10% (providing the 15% does not exceed his tugs rated maximum ball load.)

You could try locating your spare wheel to the draw bar. This will get a heavy weight forward of the C of G.

PeterD

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AnswerID: 254417