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View Full Version : Single versus tandem axles on caravans



graham.murfett
15th January 2020, 10:34 AM
G'day all

After 3 decades of my wife saying "don't even mention it" she now wants to go on weekend caravan trips.

I have been towing trailers off and on etc for decades and prefer long drawbars and single axles (weight appropriate) with safe weight distribution.
But caravans seem to have short drawbars.

Is there opinion on whether a single or double axle is safer to tow, considering the we are looking at a trailer up to about 19 feet & <2 tonnes empty.

Tow vehicle will be a recent 4x4 type diesel ute.

Thanks

Chris Parks
15th January 2020, 01:56 PM
Re the tow vehicle, do some very careful research about that, many Utes literally break the chassis just behind the cab due to weight on the towbar. Also total weight is an issue with these vehicles, don't believe the sales man when he starts trotting out numbers is my advice and get some advise from others who know what they are talking about.
ute chassis broken - Google Search (https://www.google.com.au/search?hs=HRH&q=ute+chassis+broken&tbm=isch&source=univ&client=opera&sa=X&ved=2ahUKEwiSpLKUzYTnAhXXWisKHbcpDAwQsAR6BAgHEAE&biw=2048&bih=1050)

graham.murfett
15th January 2020, 06:06 PM
Bl**dy hell. There seems to be a lot of Nissan & Mitsi's in that lot ;) Thanks for the link.

I have been researching. I found this link informative
Everything you need to know about towing heavy trailers | Practical Motoring (https://practicalmotoring.com.au/car-advice/everything-you-need-to-know-about-towing-heavy-trailers/)

It does make reference to distance of hitch from rear axle ie shorter the better, which would be ONE of the contributors to broken chassis.

ian
16th January 2020, 04:24 PM
I have been towing trailers off and on etc for decades and prefer long drawbars and single axles (weight appropriate) with safe weight distribution.
But caravans seem to have short drawbars.

Is there opinion on whether a single or double axle is safer to tow, considering the we are looking at a trailer up to about 19 feet & <2 tonnes empty.

Caravans have shorter draw bars because doing so allows more length for the van.

Dual axles on the van will give you more options for fitting the load within axle zone of the van itself.

graham.murfett
16th January 2020, 06:14 PM
Thanks ian

KBs PensNmore
16th January 2020, 10:39 PM
Plus the fact (as far as I know) tandems tow a lot better (stable) than single axled units. Especially when the wind/suction from passing semitrailers going in the opposite direction.
Kryn

aldav
17th January 2020, 10:58 AM
Surely it's the distance from the towing hitch point to the front axle of the trailer that matters rather than the length of the draw bar?

ian
17th January 2020, 02:08 PM
Surely it's the distance from the towing hitch point to the front axle of the trailer that matters rather than the length of the draw bar?
my understanding is that caravans have a maximum length that includes the draw bar and hitch, and to maximise the available van length -- i.e. the length of the caravan body -- the draw bar is made as short as is possible.

KBs PensNmore
18th January 2020, 12:46 AM
There is no maximum length of a caravan as such, the limiting factor is that the combined length of the towing vehicle and towed vehicle (caravan/trailer, etc) must not exceed 19 metres in length.
Probably the reason for shorter caravans, is that the modern vehicle has a lower towing rate than what used to be available, hence we don't see too many of the larger caravans anymore.

I found this on Google
, it has a towing capacity database that will sort you out. Select your towing vehicle from the dropdown menus below and also – just to be sure – check your car's owner's manual as well.
Towing Capacity: How Much Weight Can My Car Tow? | CarsGuide (https://www.carsguide.com.au/towing-capacity)

The big question is: how much weight can my vehicle tow? Towing capacities can range from 640kg (unbraked) and 1200kg (braked) in a compact AWD SUV, to 750kg (unbraked) and 3500kg (braked) in many large SUV wagons and dual-cab utes, through to the 6989kg (braked) towing capacity of a Ram 3500 pick-up.

What does amaze me is that a vehicle/towbar can have a max towing weight of 4.5 tonnes. When you look at the 4.5 tonne ball it's 75mm diameter with a shaft diameter of approx 30 mm, yet the whole thing relies on a little 16mm pin of probably mild steel in the Hayman Reece style towbars???
Kryn

Tonyz
19th January 2020, 02:39 PM
not putting down whats already been said, my 2 bobs worth is RACQ technical, The RAA tech guys down this way are usually very helpful, if its a real dicey issue (Ive been known to ring up 3 different times and (luckily) got different people each time, giving their thoughts)

Just yesterday returning home I came across a 'van down on its drawbar and a funny looking Mitsi ute looking like someone had stood on its middle and it snapped. The owner driver was rather stroppy, but even I knew he was towing more than it was designed for, was tempted to leave him, but waited for tow truck arrival (mate of mine) and he fair ripped into the driver for stupid weight ratio.

damian
19th January 2020, 05:05 PM
As Aldav said the drawbar is irrelevant, it's the distance to the axle that matters. A drawbar really only has to be half the width of the towing vehicle. A much longer drawbar will give you slightly bigger angle before it hits your bumper but it's hardly any difference.

The 16mm pin is in shear, the towball is in bending. The towball will probably yield and snap long before the pin.

I thought the really long vans went out of style because vanparks stopped catering to them. They have more recently offered specific extra large sites for the new big rigs.

One of the traps for vans is the total weight of the rig. My ute is a 1 tonner and has a 2300kg bar. If I put the full load in the tray then hooked up a 2300kg trailer I'd be overweight. If your van is heavy and you load up your ute with people luggage tinny whatever you can be illegal.

Tandems add weight and make the trailer harder to turn at low speed, singles are limited in load capacity (I thought it was 1500kg ?) and more prone to sway in side winds and hobby horsing.

I've always been astounded at how badly caravans are designed and built. They use the most labour intensive and leak prone construction you can imagine to make a flexible structure that starts tearing itself apart from day one. They also show no understanding at all of aerodynamics.

Anyway...