Bouncing when towing

Yeah I've never felt anything towing. I run 42psi in the rear when towing.

I tow a heavier van and with a ball weight of around 260kg and dont notice bouncing. Some possible things to try:

Are you using a weight distribution hitch? If so suggest you remove it as it is not meant to be used on a D4.

Ball weight is meant to be around 10% of the weight of the van. Your ball weight seems light for the weight of your van. Maybe try moving some heavy items forward in the van. Ball wight should be close to 280.

Do you have any significant weight on the very rear of the van. For example two spare tyres, tool boxes, outboard moters, generator? They may also cause bouncing (and sway).

thats my 2cents worth...

peter

Hi all and thanks for the replies

WDH - dont use them

Ball weight is what is on the van compliance plate. I've wondered if this is on the light side. Just not sure of the legal and insurance implications.

Nothing on the rear bar except 1 spare wheel, though I'd love to do more Im not gaim due to what was spoke of re increased pitching and yaw.

I'll do some more research on pitching but will talk it over with Rick (local LR service specialist). It could be all in my head which is what is holding me back from replacing the suspension. Silly to spend the $ when the result may not justify it and I could buy more toys....

Ten percent BW is an urban myth,,
its just a very convenient number for van manufacturers to dodge engineering shortcomings.

and if its bouncing,, it has to be bad shocks,, [bigsmile1]

We only tow a light van with ours (about 1.8t guesstimate) and haven't noticed any problems. But when glancing through the handbook recently I did see that the distance between the pin holding the tongue in and the ball/spigot was shown as 150mm or 6".
Is this an important measurement does anyone know? It seems to be just for Australian vehicles.
AlanH.

We tow an AOR Quantum Plus with a down ball of 250kg and 2500kg tare for the van. We run around 2300kg fully loaded. The setup is very well balanced and we can fine tune that as we have JC at the F&R of the camper. Our car is only 2.5 years old so still fresh in the suspension. I suggest getting your down ball measured as well as taking a close look at weight distribution through your van to make sure it is low and evenly distributed. There are several excellent websites to help in this process.

Having moved from towing a 1000kg Ultimate I thought we would notice a large difference in handling but once you get used to the additional weight the car performs perfectly. Our fuel consumption has only gone up 2l per 100km which is where I hoped it would be

Rob

As others have noted, at that sort of mileage I would be suspicious of the dampers.

Very rough rule of thumb is when you change tyres look at dampers.

Very little low speed (ie. under 4"/sec shaft speed) rebound and bump valving are often used for ride comfort, and it may be that the natural frequency of the air bags and maybe even the tyres is matched by the van towbar bobbing?

Unusual, but not unheard of.

I've had it once where we went right outside the damping range of some racecar shocks with the spring rates we were running.
The spring/tyre oscillations quickly escalated to the point the car bounced off the track.

I noticed when on a trip recently, fully loaded but not towing, that the D4 would wallow after dips. It would fore and aft rock for one or two oscillations before settling down again. I put it down to the air suspension.

As others have said, I would check your suspension was okay.
If it is then look at the weight balance of the van. A 180kg ball weight sounds a bit low for a 2600 kg van. If the ball weight is too low the van might be lifting up on bumps. I'm sure someone can describe that in more technical terms, but I hope you know what I mean.
Are your rear tyre pressures high enough for your towball weight?