recently I replaced my tow vehicle and with it a problem with stability has arisen. It is just a twitch and at times worries me. I have previously posted just now full information but this is the short version. Van and car are perfectly level . Vehicle has auto leveling air suspension. Would you think if I purchased a towbar tongue maybe two inches lower that could be the icing on the cake. I have lowered the tire pressure on the front tyres, filled up the water tanks ( 2@front of axle)
Welcome to the Forum Paul.
I assume you have a tandem axle van and are currently having a TBW of approx 10% of caravan's gross weight.
Yaw, (sway) can be generated by; unstable loading, fluid sloshing in a rear mounted grey-water tank, dicky independent suspension, erratic driving, severe swerving, too much weight behind van's axles, etc.
Tell us what suspension system you have, whether the van is off-road (high), is there any stability control (ESC) fitted, are you towing with a weight distribution hitch (WDH), are the tyres in good condition, etc?
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Possum is asking the correct questions and if you have answers to them then suggestions can be made.
If you don't tow with a WDH then maybe borrow one and try it out. I use a 600 lb Hayman Reece, purchased for Repco, 800kg is too rigid for my setup..
I tow a 2019 Jayco Journey 21.66, (Dual Axle Touring) I make sure it's 2600kg max (weighbridge weight), the max for my set up is 2700kg, when fully loaded, this is close to the max for my 2012 BMW X5 to tow and I definitely need the WDH to raise the rear end and to transfer the weight from the back wheels to the front wheels of the car (4 paws equal weight).
budget wrote:Van and car are perfectly level . Vehicle has auto leveling air suspension.
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I have lowered the tire pressure on the front tyres, filled up the water tanks ( 2@front of axle)
I am guessing there is too much weight on the towball, but without actual details it is only a guess. Are you able to turn off the self levelling suspension feature so you can see how much the rear is sagging? Would just connecting while the vehicle is switched off enable that?
What vehicle do you have? Do you have actual weights of the van when laden ... separately for wheels and towball? Depending on how far forward of the axle the water tanks are, the water could add around 50kg to the towball download.
i had a post explaining everything but unfortunately it is in the sky somewhere so Ill attempt to give you the whole picture.
i have bought a new vehicle and am now out on my first trip. My previous vehicle was also a bmw x5 tdi and if the new one is as good then happy days. So I am experiencing a slight rear wobble at speed Which I know that if I need maximum speed I could get into difficulties. My new vehicle is an Audi SQ7 it comes in at 2.5t so thats a great start. The vehicle comes with auto levelling air suspension. Both caravan and car are perfectly level when hitched up. The van is a golf Lindwood it comes in at around 2.6 ton fully loaded. Tow ball weight is 260 kg.
i have filled both water tanks up and they are both in front of the axles ( twin axel van). I have lowered the tire pressure on the front wheels 40 psi front 45 rear. I cannot fit a wdh on the car because it will fight the air suspension. Prev vehicle had a Andersen hitch which was very very stable.
the setup I have is good and in the right conditions is good but when you make a decision to overtake we all need everything in our favor.
my question and advice I need is with all things being equal if I purchased another towbar tongue and got one that is two inches lower do you think it could give me just that little bit of improvement I need.
Had a quick look online at an Audi SQ7. Seems like a really nice vehicle.
Are these the specs (downloaded from Carsales)?
Tare Mass 2465 kg
Gross Vehicle Mass 3095 kg
Towing Capacity (braked) 3500 kg
Maximum Towball Download 350kg
Do you have the rear axle load limit (probably in the owners manual or brochure)?
You said the van towball download is 260kg. Is that what is on the plate or what you have measured? If so, was that with or without water?
The plated towball weight is pretty meaningless because (in theory) it was the weight on the towball as it left the factory (if it was actually weighed). When laden it will usually be a lot more. With water tanks in front of the axles it will be a LOT more when they are full.
Again, the self levelling suspension may be hiding how much the tow vehicle is affected by the towball download. With the vehicle switched off before you lower the coupling onto the towball, will that disable the self levelling? A weighbridge will give the actual weights but seeing how much the rear end sags is a starting point.
If you have identified a handling problem, you REALLY should get actual weights on all wheels from a weighbridge. Without those figures, any answers are only guesswork. Actual weights comes first, then talk about levelling.
With the van, you say it has independent suspension. So presumably it is not load sharing (i.e. as you go over a speed bump, the front axle takes almost all the load, and when the front axle has passed it, it carries almost no load). With such suspension, keeping the van level is more important.
In the meantime, by feeling tyre temperatures after a few kilometres on the highway you can get an appreciation of any axles that are taking more load and needing higher pressures. Just a quick tip until you get actual weights.
-- Edited by Are We Lost on Tuesday 30th of July 2024 02:16:32 PM
Thankyou so much for taking the time to reply. Yes those are the weight figures of my vehicle. I averaged 12 Lph @ 95 mph on the way for my trip to pretty for a vehicle that weights so much.
im thinking of booking a meeting with a mobile weigh bridge operator to get some real figures.
i very rarely have much in the back of my car when on the road but am mindful of tow ball weight transfers to the car . there are times when conditions are good everything rides well but I need it right for when its not. I realize that just about everybody towing a van is over on the rear axel but I think Im probably borderline.
what do you think of getting a bit lower towbar tongue?
If the van is pushing the car around, extending the towball tongue will only make things worse. The reason is that the trailer tries to muscle the car around. Extending the towball tongue increases the leverage on the car, therefore making things worse. Towball weight plays a big part as well, and increasing the distance from the rear wheel centres will reduce the loading on the rear wheels very slightly, but the extra leverage will more than override the rear wheel loading effect.
budget wrote:what do you think of getting a bit lower towbar tongue?
You said the van is level now. If you lower the tongue it will no longer be level, so that would not be a good idea. If you have load sharing suspension in the van then it matters less.
Yes, a good idea to get a professional mobile weighing done.
I would not say just about everyone is overweight on the rear axle. Yes, it's probably the easiest rating on SUV styles to exceed, and probably many owners don't know or turn a blind eye. But I think it's still a stretch to say just about everyone is overweight.
In your case with identified handling problems noticed it is a good thing that you are seeking advice and looking to solve it.
Also, just as a process of elimination you could get the van suspension checked and maybe a wheel alignment. If the same tyres have been on for a while, examination of the tread wear may highlight any issues. Usually, truck wheel aligners do a good job, and without the delays waiting for caravan specialists.
-- Edited by Are We Lost on Tuesday 30th of July 2024 03:44:37 PM
I think you need to revisit you setup starting with the auto leveling switched off.
It's all about the basic's.
With the van and tow vwhicle laden as if leaving on your journey, these are the steps you need to consider.
1. Establish the towcoupling height, with the van unattached on a level surface, level the van using the jockey wheel and spirit level. with the van level measure height of the towball coupling.
2. Ensure you measure the front and rear axle heights at the wheel arch of the tow vehicle on a level surface. Now set the towball height to match the coupling height equal to, or plus 25mm.
3. Now connect tow vehicle and van together, if both units appear to reasonabally level after taking all the weight off the jockey wheel, now is the time to test drive the combination.
Notes if the tow vehicles front axle has risen greater than 50mm and rear of the tow vehicle and front of the van is low, then you may have to check your towball weight is right, or you may need to redistribute the load within both the caravan and tow vehicle, to get the front axle height back approximatly to the origional measurement or plus 25mm.
Another thing to consider is your tyre pressures, check the tow vehicles tyre presure chart, it generally has asticker on the drivers side door, eg. my tyre pressures are F 32, R 50 psi and the van is 50 psi.
As last resort you may require a weight distribution hitch ( awaiting naysayer comments)
That you for the reply , but I had no mention of extending the towbar in my post it clearly states asking the question about lowering the tongue by two inches Allowing the van to be slightly leaning down.
Thankyou so much for offering your advice. I refurbished my suspension last year , replacing the shock absorbers and all the pins and bushes. I also replaced all the tyres with new Toyo all terrain light truck tyres. I was making a generic statement when I said ?everyone ? I certainly believe I could say a good percentage of people would probably be nudging if not over on the rear and front axle weights me included. the wheel alignment is I assume fine as my tyres for the last ten years worn perfectly.
do you think just dropping the front a little could help?
Thankyou so much for offering your advice. I refurbished my suspension last year , replacing the shock absorbers and all the pins and bushes. I also replaced all the tyres with new Toyo all terrain light truck tyres. I was making a generic statement when I said ?everyone ? I certainly believe I could say a good percentage of people would probably be nudging if not over on the rear and front axle weights me included. the wheel alignment is I assume fine as my tyres for the last ten years worn perfectly.
do you think just dropping the front a little could help?
No, because you must get the setup correct in the first place, when complete turn the auto leveler bac on.
Tyre pressure when hot is ideally 4-6 psi higher than cold, tyre pressure can play a big part in wobbles, if the tyres are showing a psi in the range okay then it can be a lazy spring or shock on van or it may need some weight redistribution inside the van, just sitting level is only part of the solution, too much load at rear or even too high will cause it to wriggle at speed or when a bump is hit, ideally a van should recover in no more than 3 wiggles of the tail if the tug is throwing as well then it is a suspension/load problem I have found .............. distributing load experiment using jerry cans of water placed in various positions is a good way to help solve distribution problems in van ....
I don't put a lot of faith in tyre placards as different tyres require different pressures far better to just use them as a starting point and go from there, infact the plate on van should be ignored and only ATM and axle capacity be taken seriously the rest is often mythical ....
-- Edited by Big Mal on Thursday 8th of August 2024 07:12:48 AM
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