Towball too high

[bopeep]

Hi just bought a new tow car a chevrolet Orlando, as the car was a new model I had to have the chevy tow bar supplied by them it comes with a swan neck and is detachable.
When I hitched the caravan Bailey pageant on it was quite a bit high, after loading it was still high. Looked underneath and it appears there was only one place to fit it and no adjustment. has anyone any ideas what I can do apart from a few bags of cement in the boot.
Thanks

 

[Parksy]

The height from the ground to the centre of the towball should be between 350 and 420 mm when the tow vehicle is fully laden but not with the caravan attached.
If the towball height is within these parameters then providing that your caravan is correctly loaded and no weight limits are exceeded either for the towcar or the caravan a nose up attitude for the caravan should not affect the stability of the unit.

 

[bopeep]

thanks Parksy,
I will measure it as soon as I get it on level ground at the moment the rear end is hanging over some concrete, ( Drive a bit small )
I have towed it about 1800 miles and it seems steady enough. It is just that I have read that towing high at the front is a no no

 

[bopeep]

Hi parksy me agian,
I have just measured it with me sitting in the boot I am heavy but the back did not go down much. To the centre of the ball about an inch from the top is 460 any help appreciated

 

[Lutz]

The height from the ground to the centre of the towball should be between 350 and 420 mm when the tow vehicle is fully laden but not with the caravan attached.

That's not correct. If the car is fully laden, it makes no difference whether the caravan is attached or not. If the car is already fully laden before the caravan is attached then it will be overloaded afterwards.

It is just that I have read that towing high at the front is a no no

I know that several sources warn against the towball being too high, but none have explained why. I cannot see any logical reason why a nose up attitude is to be avoided, so long as the noseweight is measured at that height, other than the purely practical one of losing ground clearance at the back of the caravan.

I have just measured it with me sitting in the boot I am heavy but the back did not go down much.

With just you sitting in the boot the car will hardly be fully laden. It is, however, a distinct possiblity that the wrong towbar was fitted or one that is unsuitable for your car. You should have the dealer who fitted it check with the towbar manufacturer for this possibility. Sometimes, for example, there is a difference between towbars if the car has self-levelling suspension or not.

 

[senetor34]

if you tow with your tow ball to high it will push your suspension up and your overun system might not work therefor your van brakes wont be working and the van might jack-knive

 

[Parksy]

The height from the ground to the centre of the towball should be between 350 and 420 mm when the tow vehicle is fully laden but not with the caravan attached.

That's not correct. If the car is fully laden, it makes no difference whether the caravan is attached or not. If the car is already fully laden before the caravan is attached then it will be overloaded afterwards.

The way that I read the information (which admittedly is second hand) was that if the car was loaded to it's maximum weight (GVW) then the downforce of the caravan onto the towball would mean that the GVW was exceeded.

The towball is at the top of it's permitted height so make sure that both car and caravan are correctly loaded, use the right amount of noseweight and ensure that all tyres are correctly inflated. If in doubt - get it checked out!

 

[bopeep]

Hi Lutz
The car has just been launched by Chevrolet and it was the only tow bar that they supplied, It is impossible for me to return for checks because I left the country within a week back to Spain where I live. Hopes of getting action here are zilch the Spanish have a different attitude to tow bars they have to have an MOT and a caravan has to as well with a separate number plate. that is why I bought in the UK
I have crawled under but all seems to be bolted to the right places.

 

[hgv dave]

high towball = cracked shins................how many of us have done that in the past?

hgv dave

 

[Lutz]

Hi Lutz
The car has just been launched by Chevrolet and it was the only tow bar that they supplied, It is impossible for me to return for checks because I left the country within a week back to Spain where I live. Hopes of getting action here are zilch the Spanish have a different attitude to tow bars they have to have an MOT and a caravan has to as well with a separate number plate. that is why I bought in the UK
I have crawled under but all seems to be bolted to the right places.

The towbar should have a manufacturer's plate showing a EU type approval number. Even if the towbar was supplied by Chevrolet it will not have been made by themselves but will have sourced it from one of the major towbar manufacturers.
If it is an original Chevrolet Parts and Accessory item, they should be able to trace the approval number for you. Any dealer, including one in Spain, should be able to assist. Otherwise, you would have to have a look at the plate for the towbar manufacturer's name and contact him yourself, giving him all the details and pointing out that you are of the opinion that the towball is too high. It is conceivable that there was a design error on his part and this has gone unnoticed as yet because it is such a new model.

 

[Lutz]

The way that I read the information (which admittedly is second hand) was that if the car was loaded to it's maximum weight (GVW) then the downforce of the caravan onto the towball would mean that the GVW was exceeded.

Correct.

 

[ProfJohnL]

There are some possibilities here, Some cars are exempt from the tow ball height limits. The manufacture should be able to tell you if the chevrolet Orlando is exempt or not. Lutz has a handle on the requirements.

There is no technical reason why caravans should not tow nose up, however some manufactures do state the out fit should be nose level or down but give no reason for it.

However there is a slightly more pressing concern. I looked up the chevrolet Orlando on the Chevy UK web site. The braked trailer weight is an astonishingly low 1100Kg for the 1.8L models rising to 1500Kg for the rest of the range

I then looked up the Bailey Pagent 7 range and the smallest MIRO is 1118Kg. In other words all of the range is legally too heavy for the 1.8 chevrolet Orlando to tow!!!! - even empty!!!!!

 

[Lutz]

There are some possibilities here, Some cars are exempt from the tow ball height limits. The manufacture should be able to tell you if the chevrolet Orlando is exempt or not. Lutz has a handle on the requirements.

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As the Orlando is not an off road vehicle, it is not exempt from the towball height requirements.
Bopeep has mentioned elsewhere in this forum that he has bought an automatic Orlando. This has a 1500kg towload limit.

 

[Icemaker]

was it not agreed a while back that the reasons for not towing with a nose up attitude was that the amount of air going in from the front of the van did not have enough exit area at the rear of the van resulting in instability due to the rear of the van being lifted by the air trying to escape ?.
even my transit tows with a nose down attitude as did the galaxy the s max the alhambra the 406 and the discovery, i would be rather concerned esspecially since it has already been pointed out that if you brake hard the caravan will tend to push the nose even higher potentially reducing the weight of your tow vehicles rear end further off the road and reducing wheel grip, the reverse is true with nose down slightly the inertia from the van slowing will push your tow car in to the road and increase grip.

 

[bopeep]

I have been on to the company that fitted the taw bar and they tell me the the tow ball height should be between 14 and 17 inches well I exceed that at 18 inches I am trying to get hold of the garage that supplied the car. I bought the car first and looked for a caravan that would be within the limits which the Orlando auto is well in at 1500kgs What it really want is a shorter neck by a couple of inches,
The Prof advised getting on to the manufacture which is my next step.
All advice gratefully accepted

 

[xtrailman]

Have you asked if the wrong neck has been fitted. ?

Bailey stress in there unicorn manuel NOT to tow nose up.

Can the experts from previous posts give any logical reason for towing nose up?

If i had a choice, i would always tow level, nose up or down makes no sense to me.

Same as the EU height limits for tow bars, time was you could use a drop plate, legally, which in the past i have done more than once, still got a couple in the garage which i made from stainless steel.

 

[ProfJohnL]

Hello Icemaker

No it was not agreed. There is insufficent hard scientific evidence to draw any conclusive outcome.

Nose up is just as much a popular myth as "never tow above 100%", "85% is the ideal towing ratio" and "is the 7% ideal nose" loads. all these are just uninformed myths and with the exception of 100% ratio for category B drivers non have any legal standing.

The Facts are on tow ball heights are:
The EU regulations set the correct range of tow ball heights for normal private vehicles are 350 to 420 mm. Every caravan manufacture knows these figures and will design thier caravans to tow correctly with that range of TB heights.
If any caravan is nose up within that TB height range then it blows the myth of only nose down out of the water.

Now haiving put the black and white case, its not to say that there arn't shades of grey, some outfits may behave better in a nose down configuration, but its not simply the angle of the trailer, it will be to do with airflows around the whole outfit, not just the trailer. Technically it is possible that some outfits may be more stable in a nose up attitude.

With regards to the transference of braking force, asuming the caravans over run brakes are operating then the additional force on the car is limited by the force necessary to compress the overrun brake. As the caravan barkes apply the forces balance and the thrust on the tow bar is kept surprisingly small compared to the weight of the trailer. Equally as the caravan brakes apply, the inertia tries to rotate the caravan forwards which contray to your assumption actaull increases the down force on the tow ball rather than lifting it - However if teh trailer barkes are not working proprerly there will be more thrust on the car, but even then the deceleration will still tend to incraese nose load rather than reduce it.

 

[Lutz]

Have you asked if the wrong neck has been fitted. ?
Bailey stress in there unicorn manuel NOT to tow nose up.
Can the experts from previous posts give any logical reason for towing nose up?
If i had a choice, i would always tow level, nose up or down makes no sense to me.
Same as the EU height limits for tow bars, time was you could use a drop plate, legally, which in the past i have done more than once, still got a couple in the garage which i made from stainless steel.

Yes, it is possible that the wrong neck was fitted.
There is little point in Bailey stressing not to tow nose up if they don't say why or what the potential risk is if their recommendation is not followed.
There is no reason why one should tow nose up but if the conditions dictate, I can't see what's wrong with it.
If your car and your caravan happen to be level, then this is pure coincidence as production tolerances and differences in payload in either vehicle can just as well result in either a nose up or a nose down condition and both still be within the limits specified in the regulations.

The Facts are on tow ball heights are:
The EU regulations set the correct range of tow ball heights for normal private vehicles are 350 to 420 mm. Every caravan manufacture knows these figures and will design thier caravans to tow correctly with that range of TB heights.

The same regulation that specifies a towball height of 350 to 420mm also specifies that the coupling on the caravan shall be between 395 and 465mm above the ground when the caravan is standing level. Therefore, a towball on top tolerance and a caravan on bottom tolerance will inevitably result in a slight nose up attitude.

 

[Icemaker]

This is a copy of one of the pages on the national caravan council web site, right at the bottom is a link to the site with all the authorative information you need, it does seem to me from a little bit of "google" research that 98% of caravanners agree that you should not tow nose up, the caravan club also advice that towning nose up is incorrect, i still believe that i have seen a video some where which i think was produced by either swift or the explorer group showing how bad a caravan with a nose up attitude was.
One of the best things to do is when you drive your car next put your hand out of the window, with your hand level you will find that the wind has little effect now tilt your hand down to simulate a nose down caravan and your hand and arm will be forced down towards the road as a caravan would with the wind hitting the roof, now tilt your hand up and feel the air rushing under your hand and forcing your arm in to the air, same as a caravan would with the air rushing underneath on to that big solid flat piece of wood that is now acting like a wing, the caravan weight on the road is rediuced so is its ability to grip and so it becomes more unstable.
you can spend whatever amount of money you want on studies but the plain and simple fact is if you pull a big flat surface through the air with a bigger surface are at the front than the rear then that flat surface will rise up. think mattress on car roof, you dont ever see them flapping over the windscreen do you ? they are always bent double trying to lift off the car (unless it a old jacked up car with its arse in the air lol)
PRACTICAL TOWING GUIDANCE
Experience of towing is not essential for taking up caravanning. Any driver should soon find towing a caravan
both rewarding and pleasurable. If you are at all unsure, the Clubs offer towing and manoeuvring courses.

The caravan should always be towed either level or slightly nose down.

You should always build up speed gradually to get used to the different handling and braking characteristics
when towing. A caravan will alter the performance of the car and the driver will have to anticipate potential
hazards at an earlier stage. This experience will allow the driver to eliminate sudden speed and/or course
changes by using earlier anticipation to create a calmer and safer driving environment.
The speed at which a caravan is towed is very important. The aerodynamic forces that act on the caravan at
speed may tend to reduce the noseweight, increasingly as road speed increases. At a critical speed any loss of
noseweight can cause instability and this could occur at a lower speed when driving into a head wind. Gusting
cross winds, exposed bridge sections, valleys and proximity to large goods vehicles may also initiate aerodynamic
instability. Slow down, but do not brake, to return to stability.
Speed limits:
National speed limits Car Car and caravan
Single carriageway 60 mph 50 mph
Dual or more carriageways 70 mph 60 mph
Additionally, caravans must not be towed in the outside lane of a three or more lane dual carriageway or motorway.
A good reserve of power is necessary for towing up gradients at altitude.
http://www.nationalcaravan.co.uk/images/resources/Caravan_Towing_Guide_080805.pdf

 

[Lutz]

The idea that a big square box like a caravan could act anything like an aerofoil is absurd. The changes in angle involved between nose down and nose up which could affect lift are very small and far outweighed by the effect of the sheer enormous frontal area which will always cause the front end to lift as speed increases (as in the case of the mattress strapped to a car roof described above). Whether the frontal area is an inch or two higher or lower is not going make a noticeable difference.

 

[bopeep]

Did post a reply but it must have got lost. I have been on to the manufacture of the tow bar Westfalia I have given the correct part numbers and I have been told it is the correct bar for the Chevy Orlando, they agreed the tow ball height should be between 350 and 420 but they have ben given the specifications by chevy themselves and must be strictly adhered to. The reason given that as it is a seven seater fully laden with family dog and enough gear for a holiday the the suspension will compress to the correct height.
As I do not have family or dog I will have to load the car instead of the caravan, as the stipulated figure on the ball is 75 kg and the caravan nose weight is nearer 80 almost empty it might just suit me.
Thanks for all the information I have been given it has been a great help. I will just have to accept that I can do no more.

Thanks

 

[Icemaker]

"The idea that a big square box like a caravan could act anything like an aerofoil is absurd. The changes in angle involved between nose down and nose up which could affect lift are very small and far outweighed by the effect of the sheer enormous frontal area which will always cause the front end to lift as speed increases (as in the case of the mattress strapped to a car roof described above). Whether the frontal area is an inch or two higher or lower is not going make a noticeable difference."

let me get this right, you are saying in point 1 that the caravan being a big square box can not act like an aerofoil ? but then you go on to say "the effect of the sheer enormous frontal area which will always cause the front end to lift as speed increases " you mean like a aerofoil then ? if moving air causes any thing to lift it is acting on that surface in the same way as a wing, surely this is easy enough to understand !.
personally i would stay well away from advicing another person that towing with the nose of the caravan higher than the rear of the van is not a problem unless i was more qualified than the people who say it is a definate no no, ie, the caravan council and the caravan club just to mention a few of the many available with a simple google search, its ok saying "in the absense of any real scientific information" when in the same sentance you could say there is no real scientific information to say its a myth and it is safe to tow nose high.
if you can show me a legitimate scientific test that shows that a caravan averaging 20 + feet long and almost 7 foot wide is not effected by air movement rushing under it because of a high nose then i will agree with you but untill that day i will stick to advicing not to do it along with the majority.

 

[ProfJohnL]

Hello Icemaker,

I don’t particularly want to labour the point, but your example of the mattress on the roof is nowhere near a fair comparison. Primarily because the air impinging on the front edge of the matress is already moving upwards having been deflected by the front of the car and its windscreen. The air arriving at the caravan is far more complex having passed around the sides, top and bottom of the car, I seriously doubt that anyone can accurately predict the velocity and direction of the air as it strikes the leading edge of the caravan. Also it’s no good simply considering the air passing underneath the caravan, as there are equally important aerodynamic effects to be considered around all the other surfaces of the caravan. No two outfits will be exactly the same.

It is almost as likely there will be rarefied air under the caravan which actually helps it to pull it down as lift if up. Just as Lutz points out the relatively small difference in angle of attitude are relatively small for the available range of tow ball heights.

Simply quoting the NCC page does not help – as my point is that it is the likes of these that perpetuate the unscientific myths. When asked they cannot or will not substantiate the guidance they give.

It all seems very strange that we are asked to follow guidance from a body that has done no practical experimentation or research, and told to ignore the repeatable test results from motor manufactures.

However, I don’t dismiss their aims, as none of their advice or guidance is likely to create a dangerous situation, its just they seem to expect caravanner’s to have blind faith in their guidance.

 

[Lutz]

let me get this right, you are saying in point 1 that the caravan being a big square box can not act like an aerofoil ? but then you go on to say "the effect of the sheer enormous frontal area which will always cause the front end to lift as speed increases " you mean like a aerofoil then ? if moving air causes any thing to lift it is acting on that surface in the same way as a wing, surely this is easy enough to understand !.

No, I am not saying that the lift is caused by an aerofoil effect, at all. What I am saying is that the centre of air pressure acting on the front of the caravan is way higher than the axle and this is causing a couple about the axle as its pivot point and that is what is lifting the front end.
One cannot compare the aerodynamic characteristics of a caravan with the wing of an aircraft. It should be obvious that the two are totally dissimilar, quite apart from the differences in speed involved.

 

[Icemaker]

let me get this right, you are saying in point 1 that the caravan being a big square box can not act like an aerofoil ? but then you go on to say "the effect of the sheer enormous frontal area which will always cause the front end to lift as speed increases " you mean like a aerofoil then ? if moving air causes any thing to lift it is acting on that surface in the same way as a wing, surely this is easy enough to understand !.

No, I am not saying that the lift is caused by an aerofoil effect, at all. What I am saying is that the centre of air pressure acting on the front of the caravan is way higher than the axle and this is causing a couple about the axle as its pivot point and that is what is lifting the front end.
One cannot compare the aerodynamic characteristics of a caravan with the wing of an aircraft. It should be obvious that the two are totally dissimilar, quite apart from the differences in speed involved.

but they are not dissimilar lutz they are both flat surfaces with a leading and trailing edge being pushed or dragged through air at speed.
im totally cofused how you can push this thought that a caravan front of around 45 degree's angle up to the roof can possibly creat lift ? air will naturally flow to the easiest escape route in this case upwards to the roof and over even if the van was nose high the lower front edge of the van would be further out than the roof edge. so it's simple if the air is hitting the front of the van and rising which is the easist route it will be exerting downward pressure on to the window and then up over the roof, now if that air could cause drag on the upward flow then and only then could it lift the van but it would have to be a tremendous amount of air to overcome the naturall response of a moving object to dip under deceleration and this would be the "airofoil" effect you say you are not talking about.
if the caravan was flat fronted or had a negative angle on the front then i could start to think maybee just maybee air hitting the front could potentially lift the van.
but at the end of the day this thread is not about air flow and direction the question was asked is it safe to tow with a nose up attitude, 98 % of the caravanning community seem to say no so i will go along with the majority if your happy thats your choice, two of the largest caravan information resources both say do not tow nose high they may not have done exhaustive tests but they have done enough to recomend what they say. two caravan forum contributors with no experiance of the subject really should not be advicing others to the contrary, hows that going to look in the unfortunate case of an accident, "but lutz and john said it was ok".
i am naturally very cautious in giving advice against the views of major institutions being in a very safety critical role my self i do every thing by the book regardless of how ridiculous i may find it, i drive trains down a line that i know is good for 90 mph but it has a 40 mph restriction on it so i stick to it because those who are more in the know told me to !.