I just cleaned out and reorganised the front boot of the van prior to the next trip away. While it was empty I used tow ball scales to measure the weight which read 160kg. I replaced everything including all of the WDH components and the weight went up to 200kg. At the moment the van will be between 2500kg and 2600kg once we add our clothes, a carton of beer and few nice bottles of wine it will be between 2600kg and 2700kg. The additional weight that we add will be centered over the wheels and the WDH will actually be on the car not sitting in the front boot of the van so I am thinking that my towball weight could be a bit light. Although the rig seemed pretty stable the last time we were out I did notice some sideways movement when passed by semis and even when following large vehicles I felt some buffetting when we were within a hundred meters of them.
My question is - I have 2 x 95ltr water tanks positioned forward of the axles which I have left empty when travelling do people think that filling 1 or both of them could help with stability. I figure that my current towball weight is only around 7% or 8% which is about 60kg less than the recommended 10% guideline. I believe that I have enough leeway to add the water and still remain under the GCM and also be below both vehicles GVMs.
Cheers
BB
Possum3 said
03:55 PM Jul 31, 2018
If you have the capacity to fill tanks I'd fill them both and try as you travel - It's very easy to drop the water if not getting desired effects. Start by dropping the most forward first.
C00P said
09:14 PM Jul 31, 2018
My reading on this subject suggests that towball weight of 8% is usually satisfactory. Our 20' 2.9 tonne van is towed at about 7 to 8% and is fine up to 100kph. We don't normally tow at that speed, prefer to sit around 90kph.
Our experience is that you do get a little movement as semi's go past, but as long as it rapidly damps out (ie within 1-2 cycles) then there's little to be concerned about.
Apparently, all set-ups have a "critical speed" where oscillations become unstable and build up. The critical speed is affected by the way the caravan is loaded (weight in the middle rather than at the extremities), towball loading, length of towbar, and a number of other factors.
For enhanced safety we fitted our van with an ALKO electronic stability control. The only time it has activated was when we encountered a dry creek crossing at an angle at about 85kph. The twisting action as we crossed it activated the system and the van brakes momentarily engaged.
I recently asked that question of a friend who has been in the caravan manufacturing sector for many years. He stated the towball weight can be anywhere from 8% to 15% however most people use the 10% rule as a guide. Would depend on towball download stated by vehicle manufacturer and how well the van is loaded. My 2005 Boroma van has no stipulation on towball download.
The Belmont Bear said
08:39 AM Aug 1, 2018
Thanks guys for the replies I will probably do as Possum suggested but I was just curious why you recomended dropping the water from the tank that is furtherest forward first as this would be the one this would be the one adding the most download force to the towball. I will do as you suggested but I will also try it using all 3 different options and see what happens. Yes COOP it's not really a big deal as the sway rapidly dampens out after probably only a cycle but it still can be a little unnerving. I have Dexter anti sway on the van and also anti sway on the tug but as far as I know the Dexter has never been required to operate unless its happened without me knowing. The V6 diesel Jeep is very capable of pulling the 2.7T load at whatever the speed limit is without too much effort but I also try and stick to 90/95kph even if it's just for the better fuel consumpton. Stretch Retreat doesn't actually recommend what the download on the towball should be either they just specify on the plate what it was when it was built.
The thing I would really like to do is get rid of the WDH as it's heavy and moves the pivot point further away from the back axle which probably also has an affect on stability. Unfortunately Jeep say in their manual that you have to use a WDH when towing a load which basically is greater than the unladen weight of the vehicle. I would be interested in knowing how many Grand Cherokee owners (without the air suspension) are towing vans over 2.3T without using a WDH ? I even went to Pedders this week and asked them about upgrading the rear suspension, they said they don't do a heavier suspension for GCs and I would have to install air bags. Apparently this would be double the cost of what I paid to fit them on my previous Pajero Sport as they have to run the piping and install the connections in the spare tyre well which is more difficult and takes them a lot longer to do the job.
Cheers BB
-- Edited by The Belmont Bear on Wednesday 1st of August 2018 08:40:50 AM
-- Edited by The Belmont Bear on Wednesday 1st of August 2018 08:43:21 AM
I just cleaned out and reorganised the front boot of the van prior to the next trip away. While it was empty I used tow ball scales to measure the weight which read 160kg. I replaced everything including all of the WDH components and the weight went up to 200kg. At the moment the van will be between 2500kg and 2600kg once we add our clothes, a carton of beer and few nice bottles of wine it will be between 2600kg and 2700kg. The additional weight that we add will be centered over the wheels and the WDH will actually be on the car not sitting in the front boot of the van so I am thinking that my towball weight could be a bit light. Although the rig seemed pretty stable the last time we were out I did notice some sideways movement when passed by semis and even when following large vehicles I felt some buffetting when we were within a hundred meters of them.
My question is - I have 2 x 95ltr water tanks positioned forward of the axles which I have left empty when travelling do people think that filling 1 or both of them could help with stability. I figure that my current towball weight is only around 7% or 8% which is about 60kg less than the recommended 10% guideline. I believe that I have enough leeway to add the water and still remain under the GCM and also be below both vehicles GVMs.
Cheers
BB
Our experience is that you do get a little movement as semi's go past, but as long as it rapidly damps out (ie within 1-2 cycles) then there's little to be concerned about.
Apparently, all set-ups have a "critical speed" where oscillations become unstable and build up. The critical speed is affected by the way the caravan is loaded (weight in the middle rather than at the extremities), towball loading, length of towbar, and a number of other factors.
For enhanced safety we fitted our van with an ALKO electronic stability control. The only time it has activated was when we encountered a dry creek crossing at an angle at about 85kph. The twisting action as we crossed it activated the system and the van brakes momentarily engaged.
Here's a couple of articles which you might find interesting:
www.rvbooks.com.au/page/double-pendulum-principle/
www.rvbooks.com.au/page/caravan-rollovers-why-they-happen/
Cheers
C00P
I recently asked that question of a friend who has been in the caravan manufacturing sector for many years. He stated the towball weight can be anywhere from 8% to 15% however most people use the 10% rule as a guide. Would depend on towball download stated by vehicle manufacturer and how well the van is loaded. My 2005 Boroma van has no stipulation on towball download.
Thanks guys for the replies I will probably do as Possum suggested but I was just curious why you recomended dropping the water from the tank that is furtherest forward first as this would be the one this would be the one adding the most download force to the towball. I will do as you suggested but I will also try it using all 3 different options and see what happens. Yes COOP it's not really a big deal as the sway rapidly dampens out after probably only a cycle but it still can be a little unnerving. I have Dexter anti sway on the van and also anti sway on the tug but as far as I know the Dexter has never been required to operate unless its happened without me knowing. The V6 diesel Jeep is very capable of pulling the 2.7T load at whatever the speed limit is without too much effort but I also try and stick to 90/95kph even if it's just for the better fuel consumpton. Stretch Retreat doesn't actually recommend what the download on the towball should be either they just specify on the plate what it was when it was built.
The thing I would really like to do is get rid of the WDH as it's heavy and moves the pivot point further away from the back axle which probably also has an affect on stability. Unfortunately Jeep say in their manual that you have to use a WDH when towing a load which basically is greater than the unladen weight of the vehicle. I would be interested in knowing how many Grand Cherokee owners (without the air suspension) are towing vans over 2.3T without using a WDH ? I even went to Pedders this week and asked them about upgrading the rear suspension, they said they don't do a heavier suspension for GCs and I would have to install air bags. Apparently this would be double the cost of what I paid to fit them on my previous Pajero Sport as they have to run the piping and install the connections in the spare tyre well which is more difficult and takes them a lot longer to do the job.
Cheers
BB
-- Edited by The Belmont Bear on Wednesday 1st of August 2018 08:40:50 AM
-- Edited by The Belmont Bear on Wednesday 1st of August 2018 08:43:21 AM