maxing out tow capacity with travel trailer

Solandri · Mar 9, 2017

ToolmanJohn said:
i haven't looked yet, but I am going to assume that the weights/tires label on the driver door jamb has a detail of the maximum front and rear axle gross weights. I know the max payload is about 1156 lbs (IIRC). I know the max hitch tongue weight is 616 lbs (according to the manual and the sticker).

The problem is some of the weights are based on engineering specs (7716 lb tow limit). While others are derived based on standards (EU tongue weight standard is 8% of tow weight = 617 lbs).

Actually, even the 7716 lbs may not be an engineering spec. It may be a legal spec. 7716 lbs = 3500 kg, and from what I understand 3500 kg is the maximum a passenger vehicle in the EU can be rated to tow. Several mechanics have commented that the Touareg's tow hitch is much more robustly designed than 8000+ lb tow hitches on pickup trucks. VW is just being lazy and not bothering to certify the hitch for a different tow weight in the U.S.

So if I subtracted a theoretical max tongue weight from the max rear axle weight I shouldn't be over anything there. I also should take the gross load and subtract the tongue weight (1156-616= 540 pounds) . Now 540 - 180(ME) = 360 pounds Touareg payload. This is still reasonable for me as I almost always travel alone. Some extra luggage/clothes/snacks. As long as it's not behind the rear axle, and does not get over the rear axle gross. If in doubt I would toss it a locking bin into the camper near the axles. Solved.

That's fine for a back-of-the-envelope calculation. However, an object with three support points (2 axles on the tow vehicle, 1 axle on the trailer) creates what in structural engineering is called a statically indeterminate problem. There are an infinite number of possible weights on each axle which balances out all the forces, hence there are an infinite number of possible solutions, and the weight on each axle cannot be determined from a simple load analysis.

https://en.wikipedia.org/wiki/Statically_indeterminate

That's why weight distribution hitches are able to work. By tweaking the hitch so it can also transmit a torque (instead of just being a free pivot), you're able to transfer load from the tow vehicle's rear axle to the front axle - change the weight distribution on each axle to arrive at an alternate solution. A tandem axle trailer creates even more possible solutions.

If you *really* want to know exactly how much weight is on each axle, back-of-the-envelope calculations won't cut it. Take it to a scale and have it weighed. The weight ratings the manufacturers specify are a gross simplification of a very complex structural loading problem. If you knew the tongue weigh, the exact location of the center of gravity of the trailer and car, distance between axles and hitch, spring constant of the springs on each axle, and the exact tilt angle of the tow vehicle and the trailer, then you could calculate the load on each axle. But it's easier just to take it to a scale and weigh each axle.

rich.dev · Aug 21, 2018

What Airstream did you end up towing with your TOUAREG?

Benzer said:
Your experience with towing such a
LArge trailer is reassuring. I want to go big on my first TT along with my first Touareg
Any other feedback you can give on drawbacks from towing at 30 to 35 foot trailer with a Touareg?

Benzer, what Airstream did you end up towing with your TOUAREG?

gazaflash · Aug 21, 2018

Tongue weight

ToolmanJohn said:
Keeping this old towing thread rolling.

I am carefully considering my "final" travel trailer purchase. I now own a real toy (small dual sport motorcycle) so I suppose I need a toy hauler travel trailer.

Because I can find quite few toy haulers that fall well within the Touareg 7700 pound max tow rating, I need to balance the specs and amenities of the trailer with the tongue weight limit of the Touareg factory hitch. At 616 pounds, thats asking quite bit.

I found these well made trailers from a company called ATC (Aluminum Trailer Company). They have a model called the 7X20 ( 7 feet wide by 20 feet long).

The gross trailer weight is 7700 pounds, how about that!! The fresh water tank is huge, 100 gallons capacity!! Have mercy, that's a hot tub of water if full. Fortunately the tank is JUST in front of the forward trailer axle. The load ratio is 18.8% for tongue calculations. (Full 100 gallons = 834 pounds X 18.8% = 157 pounds tongue!! Yoikes!!)

I have configured a 7X20 that has a dry tongue of 506#, and the trailer is a hair over 4000 pounds empty. Even with every piece of gear and motorcycle (278 pounds) and bikes and clothes etc I will NEVER approach the Gross trailer weight. I would never tow with more than 30 gallons while driving.

So the issue here is TONGUE weight. I cannot weigh this in person, which is true of every trailer out there. Can't get a perfect bead on it. There are no 7X20 campers near me that I could possibly get a real world measurement of.

2X 30 pound propane about 100 pounds. Propane tanks are RIGHT BEHIND THE TRAILER COUPLER. So that makes the tongue about 606 pounds right away unless I go smaller tanks, or one 30 pound tank.

2X 6 volt batteries about 140 pounds. These are actually about 6 feet from the coupler, inside the front of the coach, my estimate being it will add 100 pounds to the tongue. Ouchie. So the tongue is likely at 706 pounds.

If I loaded all my stuff evenly using a 1000 pound Sherline tongue scale, and got the tongue weight back to about 616-ish pounds, what I have figured is about 5000-5500 pounds gross trailer weight. With a tongue of 616 that makes it close to 10-12% tongue weight percentage of gross.

I figured on using WD, but I realized that those WD hitches with sway control also weigh in near 80-100 pounds!! And that weight is on the hitch in addition to the trailer tongue weight.

If others are towing in that tongue range with WD, then it probably works out.

Is there ANY evidence at all of failed Touareg hitches due too overloading?? Even anecdotally, has anyone ever heard of a Touareg hitch failure? They have been out there a long long time now. Any cracks, breaks, rebuilds or what not, or has it been smooth sailing-towing for people who "break the rules" so to speak.

I am very likely going to order the trailer and come what may, will tow with my TDI.

To measure tongue weight purchase a thing like this. It is about $40. Very easy to use. Just put it under the ball receptacle on the tongue and lower the tongue onto it and read the scale. Every person that trailers heavy trailers should use it... !!

gazaflash · Aug 21, 2018

All this talk of trailers, WD, tongue weights, calculations, GVWR etc... is leaving me disgruntled again. Has anybody commented on the electronic maps that the Touareg used when a trailer is connected? Yaw control, etc...?
The Touareg is not your home brewed cheap and nasty design. It does it quietly and without issues because it has been designed properly. This is the reason why why we have bought the Touareg.
Forget the rest.

rich.dev · Aug 21, 2018

gazaflash said:
To measure tongue weight purchase a thing like this. It is about $40. Very easy to use. Just put it under the ball receptacle on the tongue and lower the tongue onto it and read the scale. Every person that trailers heavy trailers should use it... !!

Where in Canada did you buy it?
Thanks
Richard

gazaflash · Aug 21, 2018

I bought mine in Oz when I was there and brought it back to Canada. I did see something recently around here (home) but can’t remember where!
Possibly Princess Auto? I did a search on Amazon.ca and found it but its $80 (ish). There are other types much fancier but also more expensive

https://www.amazon.ca/Ball-Scale-Su...22B74XB&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&psc=1&refRID=MY6AGY35YEEJ622B74XB

vwDavid · Aug 21, 2018

I bought one of those tongue scales in Canada at a place called Princess Auto for $20 on sale (regular $40). I initially saw it on an Australian website and couldn't find it anywhere in North America- then bam it was at my Princess Auto.

Syncro16 · Oct 10, 2018

Are there any factory upgrade specs to be able to tow more than the standard amount?

Did VW offer anything?

MG

Spiegelglatt · Oct 10, 2018

Syncro16 said:
Are there any factory upgrade specs to be able to tow more than the standard amount?

Did VW offer anything?

MG

Short answer is no, 3,500 kg is max (as I understand it) in parts of Europe for not requiring a commercial license. To have an upgrade would have resulted in little to no business. I would think in the UK 3,500 kg would be more than enough though? Also your trailers ball weight is less that North America and Australia because you all have a different approach to where the axel should go, so isn't 325 kg also ample? That said other parts of the world had several different hitches that vary in capacity alone...nothing to do with vehicle...other than perhaps R5?

maxing out tow capacity with travel trailer

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