Towing and ball weight

**JDNSW** · 17th December 2007, 08:59 PM

Originally Posted by harlie

Hi Taz - I agree with John above
I would recommend that you get as much weight on the ball as possible (your legal limit of 150kg). When I purchased my boat (gvm 2.8t) it was set up with less than 20kg on the ball and at speeds over 80k was downright dangerous, would get side to side swaying up big time. As boat trailers are adjustable we moved the axel assembly back (only about 6 inches) resulting in just under 250kg on the ball – completely transformed the setup – very stable at 100 -110k and high side winds. As I understand it, the theory is that a balanced trailer will act as a see-saw - both up/down and side/side resulting in the trailer (which is heavier than the tow vehicle) getting a mechanical (leverage) advantage over the car. This is compounded by the short wheel base and relatively big rear overhang (compared to wheel base) on the disco.
Think of a semi. An 8t truck can tow (with excellent stability) 35t of trailer – the “ball weight” is around 40%, and no overhang (actually negative) from truck rear axle to hitch point – massive distance from tow point to trailer axel – resulting in no leverage (see-saw) advantage. There are equations that mechanical engineers use for this and it involves:- 1 distance tow point to rear car axle, 2 distance tow point to trailer axle, 3 wheel base, 4 the %trailer weight on tow point. That’s why the US is big on 5th wheel trailers – they work on 20 – 30% ball weight. I think it is pretty much also agreed that a trailer (say camper) tows much nicer with a long draw bar also fitting these equations.
You can’t do much about the relative leverage advantage distances – except stretch the draw bar, but you can improve the equation easily by getting weight on the tow vehicle – a seesaw doesn’t rock with an extra 10% weight on one end.
The 10% rule is what the engineers recommend for all trailers hitched to a tow point aft of back bumper (ie standard towbar - not 5th wheel) provided vehicle spec allow it – if not recommended is max.
6% will be much better than 0-1. If in doubt have a chat with a respected heavy tow dealer.

Agree with how you put it. Interesting facts that agree with your points - the most stable tow vehicle I towed with is my Citroen DS - which has the rear bumper almost touching the rear wheels (plus zero sideways elasticity in the rear suspension, and the longest wheelbase of any normal car in the last fifty years). Also suggests why the swb Landrovers tend to tow better than the lwb equivalent - the tow point is closer to the rear wheels.

John

**Slunnie** · 17th December 2007, 09:07 PM

Originally Posted by LandyAndy

Slunnie
Ive already cracked my chassis where the rear x member welds on BOTH sides.
YEP IVE TOWED ALOT OF HEAVY LOADS!!!!!
Thats why I have 2 Stage1s sitting in the yard waiting to build a firewood mule from!!!!
Andrew

Gday LandyAndy, I reckon that leaf is the way to go for towing longevity. My thoughts are that the leaf packs spread the force through the chassis a lot better, with point loading being halved compared to a coil setup. The stage 1's would be great like this.

**Slunnie** · 17th December 2007, 09:12 PM

Originally Posted by Taz

Many thanks folks,
Very helpful and extraordinarily quick!
I will be looking for a tandem now and keep an eye out for the CoG etc.
Cheers,
taz.

I would still use a sensible ball weight with a tandem axle trailer even though they're inherantly more stable. If you do use a tandem axle setup, I would also highly recommend you get one with load sharing suspension - the ones with rockers between the front and rear leaf packs as it keeps even weights on each tyre. We run heavy towed trailers, and the ones that don't load share can destroy tyres easily if the tow vehicles ride height doesn't match the trailer as it loads one axle a lot more than the other, and the tyres may not be up to the loads. Before you know it, you cant keep rubber on it.

mcrover · 17th December 2007, 09:26 PM

Originally Posted by Slunnie

Gday LandyAndy, I reckon that leaf is the way to go for towing longevity. My thoughts are that the leaf packs spread the force through the chassis a lot better, with point loading being halved compared to a coil setup. The stage 1's would be great like this.

I'll back this up....

I towed caravans comertially for about 2 years, The main vehical I used was an 84 F350 MWB with a shortened tray and rear chassis for the very reason of having a mechanical advantage over the trailer.

I used to tow 50mm ball stuff as well as 1 1/8 and 2" goose necks and turn table 5th wheel trailers with that truck and a lot was over the 30' mark and the biggest I towed was a tri axel turn table which topped out at 44'.

I had a Deefa 110 and a 130 for a week each to work out if they would be a good replacement for the F truck and I did feel that the coils didnt give as much of a firm feel on the road as the leaves as well as Im pretty sure that it would over load the rear section of chassis pretty quick as the 130 in particular made a few creaking noises putting a 33' triaxel on it so I towed it with the effy instead.

**Chucaro** · 18th December 2007, 09:14 AM

On my Disco I 1998 owners handbook Land Rover specify:
[Quote] The recommended trailer nose wight limit is 150Kg[Quote]
However the genuine Land Rover tow bar specify a maximum of 120 kg.
If you comply with this limits and the chassis cracks, then is a job to the lawyers if Land Rover do not come to the party.
The maximun permissible towed weights for the Disco 1998 are:
Trailers with overrun brakes 3500 kg on road, 1000 kg off-road
4 wheel trailers (tandems) with coupled brakes 4000 kg on road, 1000kg off-road.
Above that to be legal a]Quote] Revised VIN plates must be obtained from Land Rover which will be issue subject to satisfactory proof that the vehicle has been fitted with an approved conversion[Quote]

Keep the car legal and with in the factory specs and you have a peace of mind.
Cheers

**Slunnie** · 18th December 2007, 10:56 AM

You'd probably be lucky as the Disco is out of warranty.

**Chucaro** · 18th December 2007, 11:11 AM

Originally Posted by Slunnie

You'd probably be lucky as the Disco is out of warranty.

Nothing to do with warranty, if the vehicle does not meet the specs and recommendations is manufacturing fault.

**Slunnie** · 18th December 2007, 11:20 AM

I understand what you're saying, and you may be right, but then look at it from LR's perspective and what would you be thinking....

**JDNSW** · 18th December 2007, 12:08 PM

[QUOTE=Chucaro;655471]On my Disco I 1998 owners handbook Land Rover specify:
[Quote] The recommended trailer nose wight limit is 150Kg[Quote]
However the genuine Land Rover tow bar specify a maximum of 120 kg.
If you comply with this limits and the chassis cracks, then is a job to the lawyers if Land Rover do not come to the party.
The maximun permissible towed weights for the Disco 1998 are:
Trailers with overrun brakes 3500 kg on road, 1000 kg off-road
4 wheel trailers (tandems) with coupled brakes 4000 kg on road, 1000kg off-road.
Above that to be legal a]Quote] Revised VIN plates must be obtained from Land Rover which will be issue subject to satisfactory proof that the vehicle has been fitted with an approved conversion

Keep the car legal and with in the factory specs and you have a peace of mind.
Cheers

Regardless of the vehicle specification, the maximum legal mass for a trailer with overrun brakes in NSW is 2500kg - and I suspect that it is the same in other states. Over 2500kg the trailer has to have coupled brakes on all wheels, and there are several other requirements as well. In addition, for any trailer, the coupling (and ball) must be permanently marked with a mass higher than the trailer mass, and, for vehicles manufactured after about 1990 (can't remember the exact date), the towbar must be permanently marked with its maximum load and the specific vehicle model or models it is designed to fit.

The majority of ball couplings and towbars have limits a bit over 2500kg, so once you go over this things get quite a bit more difficult to keep legal, regardless of what the vehicle manufacturer says.

John

RonMcGr · 18th December 2007, 12:17 PM

Originally Posted by JDNSW

Regardless of the vehicle specification, the maximum legal mass for a trailer with overrun brakes in NSW is 2500kg

I take it NSW has a set of rules for overrun AND Electric brakes?

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