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Discussion Starter #1
Please help!!!!
Hi All, Looking for an answer as I am totally confused!
I have read the posts on this and other sites but looking for experience or definitive response.
Spoke to dealer yesterday, said "Yes it is OK to use WDH on genuine towbar", spoke to VW Aust, "We do not recommend WDH on our vehicles" spoke to dealer no 2 "If not a genuine accessory (WDH) we do not comment". GREAT, so where to now?? As I am about to purchase a 2300kg van with 210kg ball I would like to have WDH to help level the outfit, used before on other vehicles and they really do make a difference. My thoughts are as the van weight is only 65% of towbar rating that surely the minimal "extra"(?) load of the WDH would be easily taken care of, I realize the WDH load would be a "twisting" moment but would have thought not that great to cause a 3500kg capable car/chassis/towbar to have any grief.........
If I can use a heavy WDH on a 2000kg capable Ford Falcon with flimsy towbar why not on my beautiful treg!:mad:
Your thoughts please!!!
 

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I use the Eaz-Lift WDH bars on an OEM towbar. Absolutely no problem at all.

Which brand/size caravan are you getting?
 

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Hello Vince,

I have used WDH's for 25 plus years. Using them on a Touareg is not an issue as long as you DON'T have Air Suspension. The construction and strength of the Touareg OEM tow bar is significantly stronger than needed for the safe operation of the typical WDH's we use here in AU. Like you I used a Hayman Reese on my VX Holden for 10 years and it was tissue paper in comparison with the Touareg. The only issue with using them on Air Suspension is the two systems will fight each other as they strive to achieve the same thing... Not good.

If you have Steel Suspension just do. Most Dealers won't have a clue.

Stuart...
 

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Discussion Starter #4
Looking at a Crusader 19.6 with ensuite.
Does your towbar tongue fit horizontally into the main towbar frame with a pin? Mine is vertical and I am told that is the issue.
 

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Looking at a Crusader 19.6 with ensuite.
Does your towbar tongue fit horizontally into the main towbar frame with a pin? Mine is vertical and I am told that is the issue.
Hi Vince,

towing a 23'6" Crusader Manhattan here.

Yep, the the tow ball/shank slides into the receiver horizontally. Mine is the same as Stuart's (Hedditch)
 

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Discussion Starter #7
SteveL and Hidditch, thanks for your responses, yep been doing a bit of ringing around, it seems the vertical fit is the issue. Still cant get my mind around the strength of these towbars and the added relatively minor forces of a WDH making it in any way unsafe!
 

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Steve

Is that an anti rattle bolt on the underneath of your receiver.
Did you add that yourself or did it come with he tow bar?
 

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Steve

Is that an anti rattle bolt on the underneath of your receiver.
Did you add that yourself or did it come with he tow bar?
that is Stuart's. yes it is an anti-rattle bolt.

have to come up with a different system for mine, as the shank is never left on the car, and I have several shanks/setups, depending on what I am towing (viz. Caravan or car trailer to the track).
 

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I found if you use the VW lockable hitch pin there is no rattle as the pin screws into the hitch (ie. into the threaded flange nut that fits inside the removable hitch) and can be spanner tightened, once tightened no rattle at all.
Bit hard to explain but I hope you get the idea.

TonyB
 

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Hi Vince,
Welcome to weird and wonderful world of towing with a Touareg. Wonderful, because it is a fantastic towing vehicle, and weird because of the restrictions VW has placed on the tow vehicle. I have the same vehicle as you (2012, 180TDi, steel springs), and even though I would prefer to use my Hayman Reece WDH, I choose NOT to use my WDH because of the notes on page 171 of my Owner’s Manual (see attached).
View attachment VW WDH.pdf
The manuals are part of the weirdness, as illustrated here;
- Under the heading Drawbar Load, it states “The maximum permitted weight………must not exceed 140kg”.
- However, it also states “Due to legal requirements (???) drawbar load for vehicles registered in Australia is 280kg. So do those crafty Germans run off a special run of vehicles for Oz with strengthening in the hitch points? I don’t think so.
- I have friends with 7L Touaregs, and none of their manuals mention anything about not being able to use a WDH.
- Then in the Warning box, “Never install a “weight-distributing” or “load-balancing” towing bracket…………..etc. That’s pretty clear!!!
There have been numerous Threads on CT on this issue, including some very technical analysis of the whole question. In summary, VW is saying that the monocoque structure of the mounting points for the tow bar, are not designed to take the twisting forces exerted by the WDH, and so a WDH should not be used. By the way, I think this is a ridiculous oversight by the design engineers. I mean, they have designed a vehicle that is legal to tow 3500kg, so how much extra design work would have been required to reinforce the tow bar mounting points at the time of manufacture???. Another by the way, as much as I have searched the Internet world wide, I cannot find a single incident where the tow bar has been torn out of the rear of a Touareg. However, you will read many comments from owners who will say “I have towed my van with a WDH for 10*****km and it’s never given me any trouble”. I think they are missing the point. This has nothing to do with the strength of the towbar, or the shank. It’s all about the gradual metal fatigue which could be occurring to the fabricated, monocoque mounting point on the car.
Back to your specific case.
When I bought my car I had the option of a VW vertical hitch or a horizontal hitch. I was told by the dealer that the vertical hitch was not suitable for a WDH, so I chose a horizontal hitch (this was well before I knew anything about the “No WDH” rule). I don’t know if that is still true, but from my recollection of what the vertical hitch looks like, I wonder if it would exert even more of a twisting force on the mounting points. It doesn’t surprise me if you are hearing that the vertical hitch is your problem. The first thing I would do is check with VW to find out the maximum load for a vertical hitch, without a WDH. If it can handle your van, then I’d go with that.
My case
I have travelled many kilometers with our 2500kg van with my Treg, without using the WDH, but I take a few steps to ease the pain of no WDH.
- As we mainly stay in caravan parks, I leave the front water tank empty, and just put a minimal amount of water in the rear water tank
- I only carry one gas bottle in the front boot rather than take a second
- My pole carrier tube is located under the van behind the rear wheels
- The van spare is located on the rear wall
In other words, I actively try to minimize the ball weight, to reduce the amount of sag to an acceptable level. I know the books recommend about 10% of the van weight on the ball, but I get it down to about 210kg and have found the van travels perfectly well, without ever requiring the numerous towing safety features built into the Treg.
 
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Bill

This issue has been on my mind for some time so I decided to crunch a few numbers. I used the 2010 TDI dimensions and roughly measured the towbar dimensions and distance to anchor points, I assumed a 750mm torsion bar length for the WDH. Also I have assumed a coplanar field between the car and trailer.

With 250kG on the tow ball the additional axle loads (over and above static car weight) compute as -87.5kG front and 333.75kG rear.
To balance the -87.5kG uplift on the front axle (i.e. bring it back to zero) we need to apply 142.75kG at the WDH torsion bar.
so now the load on front axle is 0 and rear axle is 103.5kG

Looking at the bar geometry, at the with the car
Without WDH we have a load of -250kg (downward) plus a turning moment of +75kG.M (clockwise). The -250kg is taken as a shear load on the 8 bolts and the moment as a tension on the top 4 bolts (assuming a bolt spacing of 140mm)of 555kG (13.8kN/bolt).

With WDH balanced to 0 on front axle load at the connection is -103.5kG (downward) and -74.88kG.M (counter clockwise, coincidence same magnitude opposite direction).
Shear load on bolts reduced (approx. down to .25%), now bottom 4 bolts take the moment.

So unless the capacity of the monocoque structure has asymmetrical properties, stronger in one direction than the other it seems that it should be OK to use a WDH under these conditions.

However if the car & trailer are in a severe dip situation the load on the torsion bar will increase proportionally to how much it is bent up, this may cause the loads at the connection to rise substantially.
 

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Hi Ewie,
An interesting read, and great to get another persons perspective on this contentious issue. However, as I am not an engineer, I must admit that most of your discussion went way over my head. A couple of points I would like to clarify,
- I see you have a 2010 TDi, so my guess is that it is a 7L. Does you owners manual say anything about NOT using any form of WDH?
- you make mention about the load being carried by the top or bottom bolts. As per my previous reply, the bolt strength is not in question, only the strength of the fabricated metal structure to which the bolts are holding the tow bar. Surely you would need to know the dimensions, thickness of metal, and steel type of that metal structure, before you can do any calculations on it's ability to withstand a repeated twisting motion.
- I certainly agree with your last sentence. I think the loads imposed on the mounting points will be dramatically increased when driving on typical Ozzy roads, with deep culverts, rough road surfaces, when compared to static measurements.
 

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With regard to the OEM towbar (horizontal shank insert is all we ever got this side the pond) and WD: You gents are talking about something well discussed on here. I purchased a tongue scale and weighed just about everything many times for my set up (making use of public axel scales too)...actual weight the WD transfers via twist is minimal and I am carrying max tongue weight. So unless you really go crazy tightening the WD down not that much goes into twist. My opinion is all handling side to side motion as there are more points of attachment with WD. Just my opinion. Very contentious debate really.
I have run WD on two older (T1 and T2) Tregs with two separate Caravans...one is near max weight and touch over 32 feet in length.
 

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Hi Ewie,
An interesting read, and great to get another persons perspective on this contentious issue. However, as I am not an engineer, I must admit that most of your discussion went way over my head. A couple of points I would like to clarify,
- I see you have a 2010 TDi, so my guess is that it is a 7L. Does you owners manual say anything about NOT using any form of WDH?
- you make mention about the load being carried by the top or bottom bolts. As per my previous reply, the bolt strength is not in question, only the strength of the fabricated metal structure to which the bolts are holding the tow bar. Surely you would need to know the dimensions, thickness of metal, and steel type of that metal structure, before you can do any calculations on it's ability to withstand a repeated twisting motion.
- I certainly agree with your last sentence. I think the loads imposed on the mounting points will be dramatically increased when driving on typical Ozzy roads, with deep culverts, rough road surfaces, when compared to static measurements.
Bill
yes mine is a T2 (7L) I could not find in my manual any reference to WDH
But as aside, it states that loads given are for altitudes below 1000m, max ball weight 140kG, max speed with trailer not to exceed 80kM/Hr.

I agree that we need to know the geometry and material properties of the structural members before making any comment, that is why I stopped my figure crunching at that point. What I did find was that the moments (twisting) transferred to the structure at the connection were of equal magnitude but opposite direction for the case I considered (i.e. 250kG ball load & WDH load equal to load required to cancel the uplift at the front axle).

The fixing of the bar to the structure is via 4 bolts at each end of the bar, a moment (twisting caused by a load at a distance from the interface being considered) will result in a compression on one side of the connection and tension on the other. The magnitude of axial load at the bolts is moment divided by bolt spacing in the plain of the moment, (on compression side the load is transferred directly by towbar/structure contact, i.e. compression face bolts carry no axial load).

From my discussion last night with CT member Hedditch, I believe that the structure is a symmetrical closed section (I was not aware of this when writing the above, therefore I made the comment about asymmetry of the structure).Without knowing the material properties, I think it is safe to say that if the structure can carry a moment in one direction, then for a symmetrical section the same moment can be carried in the opposite direction.

Fatigue is a little more complex to quantify. But generally speaking the magnitude of the oscillation (particularly if it reverses in direction) has a significant impact on the number of cycles required before a given material strain hardens and cracking starts. Under normal driving conditions I would expect that the variance in the load would be relatively small and in the same direction (except the occasional extreme crossing deep culvert or speed hump). I think that WDH should probably not be used in an off road situation because of the high chance that large (vertical) angles between car and trailer could occur.

I hope that I have clarified any grey areas, and if you would like to discuss any of the matters please feel free to drop me a PM with contact details.
 

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Hello again Ewie,
Thank you for clarifying the earlier post. I now have a better understanding of what you were saying. I agree with your statement that you cannot go much further, without precise details of the structure to which the towbar is bolted.
Just out of morbid curiosity, would you please comment on the following two questions, from an physical engineering perspective.
1. In Australia, VW states that the maximum towball weight (for a 7P at least), should not exceed 280kg. So, lets say I place a towball scale under the towball and take a reading with the van attached of say 280kg. Then I attach the two spring bars of the WDH and lever them up and attach the chains to the A frame, which has now risen by say 50mm. So now the towball scale is reading something less than 280kg; say for example 250kg. I realise that some weight has been transfered to the front wheels of the tow vehicle, but what has really happened at the towball itself. Has that initial 280kg simply been shared between the towball, and the four connection points for the two spring bars?

2. Say for example, that the rear of the tow vehicle sags 60mm when the van is attached, without any WDH. In the context of this discussion on moments, and metal fatigue, is there anything to be gained in NOT trying to recover the full 60mm of sag using the WDH, by leaving an extra link or two in the working section of the chains? The end result would be a sag of say 25mm.

Regards,
Bill
 

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Bill

To answer your questions.

1. Without knowing the spring stiffness coefficient we cannot estimate what the load will be if the spring is loaded by 50mm. What I can say is that in my example approximately 1.4 times the WDH load is deducted from the rear axle i.e. for every 100kG at the WDH, the ball load is reduced by 140kG, an equal but opposite load is distributed to the front axle of the car and the wheels of the trailer according to geometry (in my example approx. 60% to car & 40% to trailer).

I reiterate statement in earlier post, we must follow the load path to understand what is happening. At the tow ball (please note that previous calc's are for loads at the axles, which will be different than those at the tow ball because of the differing lever arm length) we have the initial downward load plus a new upward load from the WDH, as far as the tow bar is concerned it only sees the summation of the loads acting (i.e. from my example +250kG (down) and -142.75kG (up) = 107.25kG, plus a turning moment of 75kG.M

2. Leveling is achieved by a combination of reducing load on rear axle (allowing it to lift a little) and applying a load to the front axle (causing it to drop a little). I believe that it is probably better to apply a little less than a little more load when using the WDH.

Keep in mind that the capacity of the structure would be related to the design loads (i.e. 350kg allowable tow ball load) so there is a Safety Factor proportional to the difference between the applied load and the design load.
 

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Ewie,
Thanks for your analysis. I also crunched the numbers and came up with broadly the same results.
One interesting aspect of the bolt loading to be considered is the loading induced by towing forces (braking, acceleration and inclines). Whilst these are unknowns, some feel for the design loads can be deduced from the car manual. Mine (2015) states that when towing on inclines greater than 12%, the towbar must be downrated from 3500kg - it doesn't state to what level though. It also states that the towball should always be loaded to its full rating (an interesting point when considering Australian caravan ball weights!). Perhaps the full loading is for the European market.
I calculate that the towing force of 3500kg on a 12% incline is about 420kg and this does not include any friction and wind resistance forces. This force applies tension to the lower bolts and will counteract and negate the tension in the upper bolts and produce tension in the lower bolts. Possibly this is why VW wants to load the ball fully, to limit the lower bolt tensions. Because the line of action is below the plane of the bolts, acceleration and inclines will produce double the tensions at the lower bolts, than tensions at the upper bolts generated by equivalent braking forces.
The tension forces generated by the towing loads add to the bolt tensions generated by the WDH and, as you say, may generally be fairly low, except on steep inclines and traffic light drag racing!
I have been monitoring my wheel deflections when using a hitch. I am currently running at 0 at the front and 35mm at the rear.
Without the hitch fitted I was running at -10 (F) and 45mm(R), with ball load around 220kg.

Steve
 

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Steve

My manual also states that a de-rating of tow load for inclines above 12%, and I agree with your figures for the load. The load on the bolts is a affected by the vertical position of the ball relative to the bolt pattern centerline. I have mine mounted with the receiver turned up so the ball centerline approx. lines up with the bottom bolts, therefore tow load is taken as a tension on the lower bolts at approx. 1.0 tow toad. It should be noted that if the hitch is mounted in the lower configuration the tension increases (i.e. if ball is lowered by 50mm the tension is 1.33 time the tow load), and likewise if the ball is raised the tension is redistributed proportionally to top bolts, with the ball inline with bolt centerline the tension is equally distributed between top & bottom bolts.

I agree with your set-up in that you have only counteracted the uplift at the front axle and not tried to completely level the Treg by transferring some more of the rear deflection to the front.


"Without the hitch fitted I was running at -10 (F) and 45mm(R), with ball load around 220kg."

How have you measured ball load, is this prior to WDH load or is it from weighbridge results?
 

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Hi Ewie and Steve104,
My head is aching after reading your posts, but it is all good info, and valuable to this discussion. I keep reading them over and over to get to the bottom of it.
With regard to measuring towball weight using a weighbridge, I have done this on a couple of occassions, but the operators have always warned me that these heavy duty weighbridges are designed to measure heavy vehicles, and so + or - 20 kgs is acceptable to them. Therefore, if you are trying to get a more accurate meaure of towball weight, you better use a different method. For example, the plank of wood and bathroom scale method, or one of the specifically manufactured towball weighing scales available from most caravan and 4wd stores.
 
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