Towing capacity T5 - something to consider

[Peter Jones]

Actually the 10% thing is pretty much urban legend, there's not a lot of science behind it. It's not even mentioned in the ADRs applicable to trailer design.

The Tow ball weights on the European cars are based on science though.

I've previously a bit of reading on the back ground and found this quote here

Among all these very precise guidelines is one major variable: tow ball load. There’s a convention that sets tow ball load at around 10 percent of the trailer ATM, but this rule of thumb developed in the days of small trailers. It’s still the practice by many North American and Australian trailer makers to specify 10 percent loadings for heavy trailers, but in Europe, where there has been considerable testing done, the tow ball load range is specified in EC E94/20 regulation as a minimum figure of 25kg and a maximum of 100kg, for trailers up to 2000kg ATM. Even above that figure the heaviest gazetted coupling for cars, light commercials and 4x4s is rated at 120kg tow ball load.

Not being one to blindly accept stuff I read on the internet I looked up the referenced regulation Directive 94/20/EC but I can't extract the same opinion on first glance, there's a few calculations to be done. I'll figure it out one day. It's an interesting read though, gives you a new appreciation of the engineering involved.

In answer to the original question though, it's pretty easy to balance the trailer (caravan) to drop the tow ball weight, you just need to pack all the heavy stuff in the rear behind the axle.

A ball weight scale only cost about $20 from a caravan shop, but you can also use bathroom scales to measure the load.

Just put an axle stand on top of your bathroom sales and adjust to read zero, and place it under the ball hitch. That's the ball weight!

On my tandem car trailer moving the car on it back and forth 4 inches will alter the ball weight from negative to 85kg.

I'm towing 1400kg with 85kg on the ball no issues. That's 6% ball weight.

[jfoldbar]

so let me get this right, you mean to say that manufacturers make trailer or caravan so that 10% of total weight is pushing directly down on the tow ball.(asuming level groung with car not moving) so lets say if the van/trailer weighs 1500kg then 150kg of that weight is on the tow bar and the other 1350 kg is over the trailer axles.so while it can pull the required weight along its not actually carrying the wieght.and your saying that some car manufacturers put the total allowable downward weight on the tow bar as 100kg. meaning the safe trailer load is 1000kg. this couldnt be the case cause i could blow all your theorys out the window.
so what then does the 10%rule mean.
by the way, i didnt learn about pulling a trailer from a book. as with most things in life, i learnt it from reality.

[Peter Jones]

so let me get this right, you mean to say that manufacturers make trailer or caravan so that 10% of total weight is pushing directly down on the tow ball.(asuming level groung with car not moving) so lets say if the van/trailer weighs 1500kg then 150kg of that weight is on the tow bar and the other 1350 kg is over the trailer axles.

Yep, That's how Australian vans are designed.

so while it can pull the required weight along its not actually carrying the wieght.and your saying that some car manufacturers put the total allowable downward weight on the tow bar as 100kg. meaning the safe trailer load is 1000kg. this couldnt be the case cause i could blow all your theorys out the window.

Also correct, the design of Aussie trailers is based largely on folklore, European cars are designed according to different engineering principles.

An Australian built 1000kg trailer is designed to place 100kg (10%) on the ball.

A European car, a Tiguan for example is rated to tow 2000kg but only allows 100kg on the ball. (5%)

so what then does the 10%rule mean.

Only that Australian design rules are way behind the rest of the world. Child restrain anchors are another example where the more modern ISO fix system doesn't comply with the ADR's inferior requirements.

by the way, i didnt learn about pulling a trailer from a book. as with most things in life, i learnt it from reality.

I learnt about pulling a trailer form real life too, I designed and built my own tandem trailer, consulted on the design with an automotive engineer, researched the ADRs and European trailer standards, fitted my own tow bars and have towed all sorts of trailers many 1000's of km.

The 10% thing is a nonsense. The new Amarok is rated to tow 2800kg does anyone really expect that to mean a ball weight of 280kg?

What about "dog" trailers that have a wheel at each corner? I've seen those rated at 2500kg and they put about 5kg on the ball.

Clearly you've got to have some weight on the ball. I say balance the trailer to put the max allowable down force as specified by the vehicle manufacturer and tow whatever weight the car's capable of.

I'm right on the max capacity of 1400kg with my Bora and I run the ball weight at around 80-85kg pulled the race car to Benalla a couple of weeks ago with no dramas.

My money's on VW engineers to specify what the car can do.

[Guy_H]

Pics of my T5 towbar that has been engineer re enforced & certified to a 230kg ball weight:

Updates on our Dual cab

Had to have it done properly - we tow cars / trailers & wanted to ensure insurance coverage

[Guy_H]

Petenkaz,

Mine was done in Brisbane as well - mind you, I had to do a heap of searching to find out who / where to get it done.

[Transporter]

Pics of my T5 towbar that has been engineer re enforced & certified to a 230kg ball weight:

Updates on our Dual cab

Had to have it done properly - we tow cars / trailers & wanted to ensure insurance coverage

Hi Guy,

Can you give us more details on your tow bar, like who made it? It could help to some T5ers.

[Peter Jones]

Pics of my T5 towbar that has been engineer re enforced & certified to a 230kg ball weight:

Had to have it done properly - we tow cars / trailers & wanted to ensure insurance coverage

I considered doing the same thing to the Bora but chose just to balance the trailer instead

You'd be doing more towing than me with a bigger variety of trailers so fully understand your reasons.

What was the work involved? For the Bora there would have been a huge amount of work to reinforce all the sheet metal in the back of the car as well as adding some poly air bags to the rear coils.

As it is I added additional pickup points to the towbar inside the rear bumper anyway.

I Imagine the T5 chassis rails would have made the task at least possible.

Nice choice of support vehicle by the way, I'm considering an Amarok next but I looked long and hard at the T4/5 before I finally went with the Bora.

[gldgti]

Ball weight....

I'm an engineer, I design stuff too, not just manage people. I also weld and build things out of steel on a weekly basis. I deal with, design and built steel products that carry oftentimes tens, and sometimes hundreds of tonnes under dynamic loading.

I have seen towbars that I wouldn't put more than a 100-200kg static load on (when driving that could easily triple or quadruple in an emergency). But a lot of towbars are, from an engineering perspective, very "strong".

The ball weight thing is less about towbar strength, and a lot more to do with stability, and the tow vehicles ability to take the extra weight so far behind the rear axle without causing damage or playing havoc with the suspension, brakes and steering.. And there's a whole other can of worms.... as the tow vehicle varies so much in weight, height, length, centre of gravity, spring rate, damping rate, not to mention the lever arms that everything is loaded on. Once again, the laws here are founded upon some rule of thumb guesses that roughly cover all bases in a very generalised way, and its for this reason that at no point can you automatically assess the actual safety of towing a particular trailer with a particular vehicle, based purely on whether the ball weight is 10% of the trailer mass.

I like vans for towing, especially the transporters. Engine all the way up the front, hard load carrying rear springs, rear axle close to the back of the vehicle all mean minimised impact from whatever ball load there is. Passenger vehicles are never as good.

[petenkaz]

Thanks for your input all, good to see some debate! Personally I think the T5 could pull twice the weight of the van, it is only 900 odd kgs, however as usual in the off chance that something may go wrong I don't want to take the chance...besides, the caravan place now know the capacity of the T5, and won't sell it to me anyways which is wierd for a salesman to make that call, most dodgy ones would count the money and leave it all up to me.
Just back from Tassie and saw Nissan x trails pulling heavier vans, they have a 150 kg towball rating...I know which I would much rather do it in! So back to my old camper trailer for now

[Guy_H]

Petenkatz,

the Towbar was modded & reinforced by Welcome to Truck and Bus Towbars Qld now part of the Aranda group - Laurie, the engineer really knows his stuff.

Now mine was a Hayman Reece.

The other day at QLD Raceway, I noticed Paul Stokell had a "new" T5 VAN (probably a 2007 model) - always curious, I checked out his towbar - it was "Trailboss" brand & there in plain sight is a sticker with 2500kg's & 250kg ball weight! I was astounded.

Anybody want to call Trailboss?