Caravan swaying

Gary and Kerry · Guru

Caravan swaying

Peter_n_Margaret · Guru

Collyn Rivers has written articles on this issue.
The facts seem to be that all caravan/vehicle combinations are inherrantly unstable over 90kph due to the 'double penulum' effect.
Some hitch systems and shock absorbers on the van may tend to reduce the problem (when a vehicle rocks sideways, the suspension creates an unwanted steering effect).
Having the hitch in front of the towing vehicle axle (ie a 'fifth-wheeler') definitely helps.

The best solution is slow down to under 90kph all the time and not get into trouble in the first place.

Cheers,
Peter

Basil Faulty · Guru

generally this annoying phenomina is cause by haveing too much weight to the rear of the van.

dave06 · Guru

incorrect loading ( imbalance) of the towed vehicle will do it every time, sometimes the vehicle comes from the factory imbalanced, I.E. water tank (typically 150 - 200 kilo's too far back,) I came across this problem as a young fellow, picked up a load of timber about 12 feet long on a 6x 4 car trailer obviously had about 6 foot of timber hanging over the back, got to 55 mph the thing took off, full view of the trailer side on in my mirrors, tyres rolling and screaming, the only way to correct was to put the foot down when the trailer was starting to go side ways and to hit the brake when the trailer was straght, after about 5 miles of this I got it back under control and never exceeded 20 mph with it on the way home, it scared me ****less, needless to say when I load a trailer this comes back to me every time, if the van MUST be out of balance make it so that the weight is over the towbar not the rear as I can atest it is VERY VERY scary, there are percentage towball loading compensation figures out there and I am sure Basil has them in his head, these should be kept on hand and after the usual loading just check the distribution weight to tow ball weight, that way you will understand just how much you can put to the back and how much you can place to the front, quite a few people been killed by doing this sort of thing incorrectly, jacknifing is a dangerous hobby at 90 kph. and if you are travelling faster than 90 kph with a van then you are an idiot anyway, if you get "steerage" through suspension you have (1) overloaded the van (2) springs too light for the job, the ammount that springs move in the spring suspension hanger (front to rear) should only be about one inch to one inch and a half, if you have more movement than that then you have a problem with weight or weak springs, either way have it looked at because you have a serious problem which will cause spring failure

-- Edited by dave06 at 12:38, 2008-09-25

Wombat 280 · Guru

It's all in the weight distribution as you said . Drove a Jayco Expanda back from Perth behind a 3Lt Patrol and never had a problem with sway . The Patrol dealers and Jayco reps all said no stabilizers required I personally think it had a lot to do with the extra drawbar length on newer vans as some older vans seemed to be all over the road . May have a lot to do with the tow vehicle especially those with independent suspension like Holden and Fords the larger 4x4's don't seem to be any bother .

Driving in NSW with a high camber built into the road design puts the balance out, that combined with the pot holes you could lose a tank in doesn't help regardless of speed traveled

Alison Spence · Newbie

Hi

My wife and I have had a similar experience. European van, same hitch. Very big sway, very scary.Tried accelerating out but did not seem to help. Sway went on for a long time. Fortunately traffic in other direction was far away. Eventually sway lessened but by that time so frightened we dont remember how or why. Keen to learn:

1. What was the original cause of the sway? Could have been sidewind or accidental small jerking of the steering wheel.

2. As regards stopping sway like yourselves we are very keen to find out if conventional action of accelerating is wrong for this type of hitch. Keen to hear if you get any more info.
regards

Bob and Alison

Basil Faulty · Guru

Alison Spence wrote:

Hi

My wife and I have had a similar experience. European van, same hitch. Very big sway, very scary.Tried accelerating out but did not seem to help. Sway went on for a long time. Fortunately traffic in other direction was far away. Eventually sway lessened but by that time so frightened we dont remember how or why. Keen to learn:

1. What was the original cause of the sway? Could have been sidewind or accidental small jerking of the steering wheel.

2. As regards stopping sway like yourselves we are very keen to find out if conventional action of accelerating is wrong for this type of hitch. Keen to hear if you get any more info.
regards

Bob and Alison

You need more weight at the front of the van, that's all. Wind gusts can start a swaying motion but if your van is loaded correctly it should just sway once and get right back behind you....

twobob · Guru

I believe what is written here is simple Castor.

Explanation, we have all got a shopping trolley that wants to go its own way. In the early days of motor cars, this was an issue for good steering, ie get the thing to stay in a straight line, without the wobbles over a certain speed.

There is a relationship between, weight and "Castor" of the axles of the towed vehicle. As has been said, too much weight to the rear of the towed vehicle, will alter the caster effect. Obviously, if the axles of the towed vehicle were at it rear, then no problem. WRONG. This would place too much weight on the towing vehicle ( ball weight).

The hitch can make a little difference, by influencing the effect, but nothing will make any real difference than getting your distribution of weight correct. I believe that the weight of the towed vehicle should be "distributed" over the axle, and sufficient weight on the tow hitch to ensure it will not disengage ie 50 - 100kg.

A simple test, is for two people ( with good backs) to lift the tow hitch and see whether they can tip the towed vehicle on its bum, easily, fully loaded.

They reason it happens (caster effect) is to do with spring distortion, at dissimilar rates - deep an meaningful. You would have notice that modern vehicles have better shock absorbers, and interactive suspensions - that means - they have addressed the repercussions of the variance between the "spring" effect of the suspension, across an axle. ie load sharing

Distribute your load, evenly, even more to the front, and I feel sure the problem of knowing whether to drive it out, or not, will disappear - nothing worse than a towed vehicle with a mind of its own, and a truck coming - stay safe - distribute your load.

-- Edited by twobob at 21:29, 2008-10-04