Caravan under Slung vs Over Slung Suspension

Richard,

Our 22' van has an ATM of 2800 kg. Roller rocker suspension.

I did look at the option of over v underslung axles but decided to go with getting an extra 75 x 50 mm chassis extension which of course raises the whole van by that amount.
To me it also gives the existing 100 x 75 chassis member some more stiffness lengthwise. How much of an advantage this is I'm not sure, but having that extra ground clearance has certainly made the entry and exit of CP's and servo driveways a much less nervous operation.
I have not had any noticeable instability even with very strong cross winds or trucks passing in opposite directions or overtaking. Doesn't seem any different from original.

Cheers
Pop

If you have a HR hitch why not turn the hitch over to get it to point up instead of down.

Will give you heaps of adjustment.

Or weld a piece of box on the A frame to lift it the 40mm

Under slinging should raise it by more like 100mm. Ive done it on trailers and boats etc over the years. No appreciable difference to the tow characteristics from what I have found, though the mathematics show there is a small one.

If you have a standard adjustable hitch you can buy a longer drop shank as shown below :

http://caravansplus.com.au/catalog/product_info.php?products_id=9520

Richard, if you only want 40mm total lift, then the better method of doing it, would be to install new (longer) spring perch brackets.

This would involve carefully cutting off the old brackets and welding the new brackets on.

A move from under slung to over slung springs is going to give you 100mm or more lift, as gbc has pointed out.
There's a substantial difference between 40mm and 100mm, and you will notice it.

The difference in ride height also makes for an increased step-up, into the van.
Doesn't seem like much, but you will notice it.
Try jacking the 'van and supporting it with jack stands at the two different heights, to see how it looks.

100mm lift will only make a difference in stability if you have soft springs.
If you have four spring roller rocker suspension, then it rates as a stiff suspension.

Cheers, Ron.

Fitting "straight" axles will lift it 50mm.

cheers

Hi Richard,
I have a 24 foot Jayco Sterling which had the axle beam fitted under the springs before I got it, by a previous owner, and I have no issues with that at all and would advise anyone wanting to do the same to do it as it does raise the clearance and does not effect handling as far as I can tell. Mind you I have not had it much above 110 and very rarely at that but usually travel around 90 with it with absolutely no problems.

We did the same thing on the mates 21ft Jayco and he reports no handling problems either and is very happy with it. He was having the same problems as you with ride height and is now very happy with the outcome. He was recently up in the NT and had it up to 130 with no issues just to see what the 200 series cruiser would do with the van on. Mind you there was not a bend in sight no doubt.

The nephew has a 21 ft Jayco and it also has the springs fitted on top of the axle beam as well for extra height and he is happy with his.

Another mate got a new Jayco Discovery and we did the same to that and he is also very happy.

My advice is do it if you are of a mind to, but,

As Rustytuba says, a straight axle is a better solution if you can afford the change over. A bit of money involved though I would say.

Cheers, Bruce.