Thread: Towing

This site
Caravan Tips
has this to say on the subject.
Note the last sentence.

The case for Weight distribution Hitches

This was a topic I personally found quite confusing so here is my attempt at an explanation.

When you drop the caravan hitch onto the towball the back of the tow vehicle drops. The instant thought is if you put heavy duty springs on the back wheels then you will restore the vehicle to level and all will be well, this is what I thought initially. It may look fine but actually all is not well.

If you consider the diagram, downward pressure (red arrow) on the drawbar means the vehicle will pivot around the back wheels (green arrow).

It follows then that the front of the vehicle (blue arrow) will come up because of the seesaw principle.

Ignore springs in this argument as they actually have no impact on the physics of the situation.

If the front has come up then weight has been removed from the steering, braking and traction.

Not a good idea as this means less control, especially when you need it in an emergency situation.

A weight distribution hitch redistributes the weight to the front wheels, something that heavier springs cannot do.

Heavier springs deal with the extra weight inside the vehicle, they cannot redistribute weight to the front wheels.

Originally Posted by vnx205

The jack is taking some of the weight.
So that is a different setup.
It's a bit like the caravan dolly my father owned in the 60's.
It was two small boat trailer size wheels on an axle with springs.
The caravan hitched onto the back and the dolly then hitched onto the car's towbar.
Like your jack under the towbar really, but quite different from stiffer rear springs.

So, to take your point further, if we are using SLS, by pumping up the rear, the weight HAS to be shifted, in this case to the front suspension. If there is a towed vehicle, it would accept some of that load.

If we are using load-levelling devices, the load, likewise, is shifted to both the towed vehicle & the the front suspension.

Originally Posted by vnx205

This site
Caravan Tips
has this to say on the subject.
Note the last sentence.

The case for Weight distribution Hitches

This was a topic I personally found quite confusing so here is my attempt at an explanation.

When you drop the caravan hitch onto the towball the back of the tow vehicle drops. The instant thought is if you put heavy duty springs on the back wheels then you will restore the vehicle to level and all will be well, this is what I thought initially. It may look fine but actually all is not well.

If you consider the diagram, downward pressure (red arrow) on the drawbar means the vehicle will pivot around the back wheels (green arrow).

It follows then that the front of the vehicle (blue arrow) will come up because of the seesaw principle.

Ignore springs in this argument as they actually have no impact on the physics of the situation.

If the front has come up then weight has been removed from the steering, braking and traction.

Not a good idea as this means less control, especially when you need it in an emergency situation.

A weight distribution hitch redistributes the weight to the front wheels, something that heavier springs cannot do.

Heavier springs deal with the extra weight inside the vehicle, they cannot redistribute weight to the front wheels.

I totally agree as far as standard coil springs are concerned.

However, the SLS system is designed to be a variable-load adjusting system. Therefore, it adjusts the load by adjusting its spring rating (pressure). Therefore the simple diagram you posted does not apply.

Originally Posted by Bushwanderer

So, to take your point further, if we are using SLS, by pumping up the rear, the weight HAS to be shifted, in this case to the front suspension. If there is a towed vehicle, it would accept some of that load.

If we are using load-levelling devices, the load, likewise, is shifted to both the towed vehicle & the the front suspension.

No. Pumping up the rear air springs does not shift weight to the front. Allan's diagram is correct.

Surely extra pressure added automatically to the SLS is just like adding Poly Air bags or stiffer springs.
In which case the following comments from this site
http://www.lets-getaway.com/hitches-antisway-weightdistribution.htm
would apply.




‘Weight Distributing Hitch’ (springs and levers that transfer part of the imposed mass back onto the front wheels of the towing vehicle and, to a lesser extent, the caravan).
There are various terminologies used for stabiliser bars such as weight distribution hitches, anti-sway bars and load equalisers.
When a caravan is placed on the ball of the tow hitch it places a lot of weight on the rear of the tow vehicle and changes the axis whereby there is less weight on the front of the tow vehicle raising the front wheels. This makes steering and braking less effective. Loss of traction can also be an issue especially for front wheel drive vehicles.
By using better heavy duty springs or incorporating air bags to raise the rear of the tow vehicle will have no effect on the weight distribution.



and





Will Poly-Air Bags assist with weight distribution ?

When you push down on the handles of a wheelbarrow the front rises. That's what happens to the towing vehicle when you connect the caravan - the front wheels tend to lift, therefore reducing steering control.
Adding poly air bags is like stiffening the legs of the wheelbarrow. Certainly worth doing if the originals are too weak/soft. But it does not address the real problem which is, like the front of that wheelbarrow, the front wheels of the car tend to lift.


A weight distributing hitch addresses the latter problem and is necessary to have.

The bold emphasis is mine.

Whew,

Now I guess I'm going to have to weigh the tow bar on the boat just to see what weight it does exert on the Disco

hang about.....

are we talking about load leveling hitches in this thread OR the weight distribution hitches?

Airbags do away with the need for the load leveling hitch setup but not the requirement for weight distribution....

G'day Batman,

I asked this same question HERE and found out the answer first hand.

The Land Rover manual says not to use them when towing if you have SLS, i can tell you now this is rubbish and as someone pointed out is more probably a "safety" concern than for a legit reason.

I tried towing without a weight distribution hitch and it was just plain dangerous! I recommend you DO use one if there is a reasonable amount of weight being placed on the tow ball and ignore the manual

Heres a pic of the 23ft van i tow, i dunno what it weighs especially after the missus has filled every conceivable space with stuff and more stuff before we go away.