OFF ROAD Caravan wheels

Submitted: Friday, Jun 28, 2019 at 21:09
ThreadID: 138617 Views:5550 Replies:11 FollowUps:13
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For and against what is your thoughts on whether to use and travel on dirt outback roads/tracks
A single axle or a dual axle as far as tyres go such as wear and tear which handles best in sand (I do not drive on wet roads).
Do tyres have to be very noby or as long as they are off road .
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Reply By: Peter_n_Margaret - Friday, Jun 28, 2019 at 21:35

Friday, Jun 28, 2019 at 21:35
Single axle, no question.
No "tracking", (self steering) so it follows the tug. Lower drag. Full load sharing.
OKA196 motorhome
AnswerID: 626427

Reply By: Member - reggy 2 (VIC) - Friday, Jun 28, 2019 at 21:57

Friday, Jun 28, 2019 at 21:57
sorry could explain a bit more please
AnswerID: 626428

Reply By: IvanTheTerrible - Friday, Jun 28, 2019 at 22:10

Friday, Jun 28, 2019 at 22:10
We run the same wheels and tyres as the tow vehicle
AnswerID: 626429

Reply By: Member - DW Lennox Head(NSW) - Saturday, Jun 29, 2019 at 04:47

Saturday, Jun 29, 2019 at 04:47
Up until I changed caravans, I have run BFG AT light truck tyres and rims of exactly the same size on both the tow vehicle and single axle caravan.

We have done 10s of thousands of kilometres with that set up. The good thing is that if spares are needed there are a minimum of 2 available. Some caravans have 2.

These tyres are good on almost any surface. Mine have done beach sand, gravel, mud, stones, etc. In all the years with that set up I only changed a couple of tyres as they had either a wall cut or bulge.

Excellent condition tyres before a trip will help minimise problems.

AnswerID: 626432

Reply By: rumpig - Saturday, Jun 29, 2019 at 07:14

Saturday, Jun 29, 2019 at 07:14
Size and weight of van probably determines some of the axle number question....there's quite a few vans, especially the "hybrids / crossovers" out there, running pretty decent weights on a single axle that should be on dual axles IMO.
AnswerID: 626433

Follow Up By: Keith B2 - Saturday, Jun 29, 2019 at 11:42

Saturday, Jun 29, 2019 at 11:42
If the wheels, bearing, brakes, axles, springs and tyres are rated correctly, I think you can run any weight you want on a single axle. The real issues are suspension design and weight distribution.

Modern caravans all seem to go for independent trailing arm suspension which gives excellent tracking, but a very low roll centre. This causes additional body roll which can lead to instability if you get a pendulum thing happening. It also proves very poor load sharing for dual axles, unless they are running connected air bags on each side, like on the Bruder and the Kimberley Cruiser.

Putting a lot of weight at the ends of the caravan increases the pendulum effect (called yaw or polar inertia) which, with a low roll centre, can cause real stability problems. Kimberley (bless their liquidator) used to put anti-roll bars onto their caravans for this reason.

A single axle frees us a lot of space in the caravan and will reduce weight by maybe 100 kg. It also does less track damage because there is no scuffing of the tyres on tight bends. The down side is increased ground pressure, which can be overcome by using larger tyres and dropping pressures when on sand.

IMHO, the best suspension for a single axle is a solid axle with either long, well designed leaves properly damped, or a four or five link setup, like on the back of most 4WDs. This gives a much higher roll centre. Add good dampers and bags for a great ride.

For what it's worth, here's what I've put on my build:

FollowupID: 900213

Follow Up By: ian.g - Saturday, Jun 29, 2019 at 12:04

Saturday, Jun 29, 2019 at 12:04
Excuse me as I'm a bit confused, but why would you be running Free Wheeling hubs on a trailer?
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Follow Up By: Keith B2 - Saturday, Jun 29, 2019 at 13:14

Saturday, Jun 29, 2019 at 13:14
Ian, not to many people notice this. I didn't want to use the hydraulic disks as a long termparking brake. The disks and stub axles are off the front of a 79 series, so a drum brake wasn't an option. If you look just inside the brake backing plate below, you can see the a bolt passing through the centre of the beam axle.

This holds a sawn off axle which has been drilled out to take the bolt and to hold the cut down axle in place. By locking the hub, the wheel can't rotate. It also means you can lock one wheel to manouvre the caravan.

FollowupID: 900221

Follow Up By: ian.g - Saturday, Jun 29, 2019 at 13:26

Saturday, Jun 29, 2019 at 13:26
Thanks for that keith, I'm old and easially confused, just seamed like overkill but with your explanation I can now understand how it works
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Follow Up By: RMD - Saturday, Jun 29, 2019 at 14:06

Saturday, Jun 29, 2019 at 14:06
Isn't the roll centre of your design quite low, lower than a trailing arm type? Just seems to me the highs and lows are back to front.

There is a good strength in your axle setup but will the chassis setup, riser sections allow flex and fracture if any significant weight is in the vehicle?
Is the FWH there to be a park brake? How can it be registered without a manual park brake? it isn't just a 6 x 4 trailer.
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Follow Up By: Keith B2 - Saturday, Jun 29, 2019 at 14:58

Saturday, Jun 29, 2019 at 14:58
RMD, I think (hope) I have my roll centres right. The lower the roll centre, the more body roll you get. A bit like a lollypop on a stick. Their further down the stick you hold it, the easier it is to push the lolly left and right.

The upsets in the chassis are 4mm steel rather than the 100x50 x 3mm RHS used everywhere else and are increased to 150mm depth above the air bags. There is additional reinforcement in there as well.

It's also bonded to the composite body, which adds a lot of stiffness to the structure. We'll see when it's on the road.

On the emergency brake thing, I am going to talk to the inspector next week and see if an over-ride button or switch on the hydraulic over hydraulic brake unit will suffice. I didn't realise that I had a problem until recently when I re-read the rules. I've made a dozen blunders like that.

Sorry to have hijacked this thread. It wasn't my intention.

FollowupID: 900226

Follow Up By: Member - David M (SA) - Sunday, Jun 30, 2019 at 12:06

Sunday, Jun 30, 2019 at 12:06
Looks a bit to professional for my liking. :)
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Follow Up By: Blown4by - Wednesday, Jul 03, 2019 at 13:58

Wednesday, Jul 03, 2019 at 13:58
One of the best designed and engineered set ups I have seen not being a fan of the populist trailer arm systems. I think you will find that emergency brakes have to activate automatically should a de-couple occur. Quoting from VSB1: "The brake system must cause immediate application of the trailer brakes in the event of the trailer becoming detached from the towing vehicle." Not sure how a 'press button' would do this or if you would be in a condition to activate the button should the de-couple occur resulting from a MVA. I have seen this done though by activating the electric motor on the hydraulic (power pack) over hydraulic set up using a cable attached to the tug (a la electric emergency brakes) & a battery (that you would have in the van anyway) that will keep the emergency brakes activated for the mandatory 15 minutes. Also over 2000kg GTM the service brakes must be able to be operated from the tow vehicle.
FollowupID: 900330

Follow Up By: Keith B2 - Wednesday, Jul 03, 2019 at 15:39

Wednesday, Jul 03, 2019 at 15:39
Thanks Blown4by for the kind words. I don't like the popular independent trailing arm systems either. They seem to be more a fashion statement that anything else. Why you'd need independent suspension on a single axle trailer is a mystery to me.

Just on the brakes, I have a Hydrastar electric over hydraulic unit in the system with a breakaway switch and have just added a manual switch to the outside of the van so that the brakes can be applied by one person when it's being manhandled. The locking hubs are for when it's stationary.

Apparently the requirement for an in-car brake battery monitor in NSW has just been removed. My WiTi setup flashes all the lights on the van if the voltage drops below 11.5. The brakes are powered by the 400AH lithium house batteries with 990 watts of solar on the roof, so the 15 minute requirement should not be a problem.

FollowupID: 900335

Reply By: RMD - Saturday, Jun 29, 2019 at 10:13

Saturday, Jun 29, 2019 at 10:13
Why would you not drive on wet roads? Dry roads with loose skiddy sand or gravel can be worse. A high, heavy, single axle van can be dangerous at times. They have less self correctional ability if things go wrong/sideways. If thinking of single make sure you find out the ACTUAL axle rating and the weight it IS carrying when loaded. Some run close to their limit which means less safety, failure of bearings and /or the axle. I agree with rumpig, some are too heavy for 1 axle.
For a given weight a dual axle has less tyre contact pressure on the sand and won't sink as much. You want a tyre which has the ability to clear itself as it rotates, some can continually keep grabbing the road surface.. You can't by road knobby tyres for vans. A highway tyre will instantly block it's tread if clay or mud is encountered and then you instantly have slicks which don't grip the ground much at all. Forget braking ability in that situation, they will simply lock up and skate. A compromise is an All Terrain tyre. Everything used to conditions and wise driving ensures the best degree of safety.
AnswerID: 626437

Follow Up By: Blown4by - Wednesday, Jul 03, 2019 at 14:03

Wednesday, Jul 03, 2019 at 14:03
"You can't by road knobby tyres for vans."
Whether you would want to run them or not is one thing but given the correct diameter/width rims to suit the tyres, correct offset & correct stud pattern/PCD to suit the hubs, you can fit any type of tread pattern tyre you want to a van.
FollowupID: 900331

Reply By: Rangiephil - Saturday, Jun 29, 2019 at 14:38

Saturday, Jun 29, 2019 at 14:38
I have always run commercial type highway tyres on my camper trailer which has been on many of the iconic tracks with no problems for 13 years of travel. I have never had a puncture in that time.

IMHO the thicker rubber with less voids of a commercial tyre with highway terrain type tread vs the more open "holes" in an AT or mud tread provides more resistance to spiking.
I cannot see the point of AT or mud tyres on a trailer as there is no traction involved . In fact I cannot see the sense of wide tyres on a trailer as to me it is just affectation and fashion.
Highway tyres also have more longitudinal drainage channels which help to stay in line.
Regards Philip A
AnswerID: 626446

Follow Up By: Malcom M - Monday, Jul 01, 2019 at 09:08

Monday, Jul 01, 2019 at 09:08
The size of the tyre will affect the trailers load carrying rating.
FollowupID: 900275

Reply By: Ron N - Saturday, Jun 29, 2019 at 14:59

Saturday, Jun 29, 2019 at 14:59
One often-unmentioned factor in camper and caravan stability, is tyre profile.

Low profile tyres have less wall height, which vastly reduces sway, by limiting the rim sideways movement, relative to the tread.

High profile tyres are far better suited to low-speed, off-road work, where the tyre pressure can be reduced, and the tyre "footprint" increased by a sizeable percentage.

But high profile tyres increase trailer/camper/caravan potential sway, because there is a lot of sideways rim movement, relative to the tread.

You need to pick the balance you want, relative to the amount of off-road trailer/camper/caravan operation, that you're going to indulge in.

Cheers, Ron.
AnswerID: 626447

Reply By: Member - johnat - Saturday, Jun 29, 2019 at 19:47

Saturday, Jun 29, 2019 at 19:47
Confused by the question, I am.
Do you really mean "off road"?
I think that what you mean is "untarred road" - which is NOT off road. The difference between off road and dirt road is that true "off road" actually involves driving across open paddocks or desert where there is no road at all, usually not even a track to follow.

I'd suggest that virtually nobody does actual off-road. (Unless you are in a tracked vehicle like a M113A1 Armoured personel carrier, or similar)
AnswerID: 626451

Follow Up By: Peter_n_Margaret - Saturday, Jun 29, 2019 at 20:24

Saturday, Jun 29, 2019 at 20:24
There is a lot of space between "dirt road" and your definition of "off road".
Beaches, for instance, and most of us go there. Fraser is classed as a "road".
OKA196 motorhome
FollowupID: 900241

Follow Up By: Member - johnat - Monday, Jul 01, 2019 at 17:52

Monday, Jul 01, 2019 at 17:52
If it is "classified" as a road, then it's a road. driving there is driving on a road, no?

Agree that beaches aren't paddocks, but most are not classed as roads, and would qualify as "off-road". Not many people would take their caravan onto a beach, would they? I must admit, I'm not a beach person, so would not be bothered - I prefer my water frozen and on the side of a hill.
FollowupID: 900294

Reply By: Member - reggy 2 (VIC) - Monday, Jul 01, 2019 at 11:11

Monday, Jul 01, 2019 at 11:11
Thanks everybody for your input I will put a lot of thought into which van I decide on .
AnswerID: 626477

Reply By: Batt's - Monday, Jul 01, 2019 at 12:38

Monday, Jul 01, 2019 at 12:38
Nticed you were highlighted I do not drive on wet roads wondering how you managed that I would find it very hard to avoid.
AnswerID: 626480

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