Simplicity offroad caravan suspension

[Bulletman]

positive this is almost as common as tyre topic ,but have read most threads and never really got a convincing answer.

http://www.simplicityaxles.com.au/uploads/3/1/3/3/31330617/editor/1423114980_1.png?1553671613

I fully understand how it works in principle and see its used on the PT2 haulmark military trailers and also on the early bushtrakker vans, but cant help but wonder how it goes on corrigations... these seem to be the most common encountered thing when off the black top..

So does anyone have this type of set up on your offroad or semi offroad caravan... if so how have you found it off the black top..

Not interested in debating the best suspension , just want some real world info on this type when used on a dual axle caravan.

many thanks

Cheers Bulletman

[ytt105]

I had the single axle version on a 15ft van. The suspension tore out of the chassis! It was far too stiff and offered NO suspension movement at all. I wouldn't consider any system that uses only one spring for two axles. That spring has to be able to carry the entire weight, so inevitably is too strong.
However, simplicity do make a new suspension that uses 2 coil springs, but retains the load sharing, which is a good thing.

Personally, I will now stick to live axle, leaf spring, WITH shock absorbers. Best all round if you can't afford to go all the way to air suspension.

[DoubleChevron]

I had the single axle version on a 15ft van. The suspension tore out of the chassis! It was far too stiff and offered NO suspension movement at all. I wouldn't consider any system that uses only one spring for two axles. That spring has to be able to carry the entire weight, so inevitably is too strong.
However, simplicity do make a new suspension that uses 2 coil springs, but retains the load sharing, which is a good thing.

Personally, I will now stick to live axle, leaf spring, WITH shock absorbers. Best all round if you can't afford to go all the way to air suspension.

I don't htink this design would do that. There is a major builder of these "offroad" vans that doesn't use a full crossmember so they fatigue crack the mount away. Just take a look and you will quickly pick the weak points. Eg: I just googled "offroad caravan suspenion"

https://i.pinimg.com/564x/91/dd/66/91dd660e404e8d8ebabd3a5da1af53b5.jpg

This one has the same issue with the shocker mount. That is going to rip the side out of the chassis. The tiny "stub" the shockers are mounted to need to be a full chassis member (so it can't flex and twist).

[PhilipA]

I would think that chain or strap suspension travel limiters and effective bump stops would reduce that problem greatly.
My 1997 Camp'o'matic has a roughly similar trailing arm setup with short Koni shocks (F100 twin I beam) mounted at an angle inwards, and is fitted with rubber bump stops and chains. It has been around Australia several times, and apparently the Konis couldn't be rebuilt as the foot valves were damaged which suggests some air time with overloading before I bought it. Yet the shock mounts are fine. So my conclusion is that the loading is low as long as the shock is not over extended or compressed too much.
Regards PhilipA

[goingbush]

I had the single axle version on a 15ft van. The suspension tore out of the chassis! It was far too stiff and offered NO suspension movement at all. I wouldn't consider any system that uses only one spring for two axles. That spring has to be able to carry the entire weight, so inevitably is too strong.
However, simplicity do make a new suspension that uses 2 coil springs, but retains the load sharing, which is a good thing.

Personally, I will now stick to live axle, leaf spring, WITH shock absorbers. Best all round if you can't afford to go all the way to air suspension.

Ditto,

There is absolutely no reason and no need to have independent suspension on a caravan .

Live axles are better , stronger, cheaper, don't go out of adjustment and easier to maintain. You can have exactly the same spring rates and shockers as independent without the issues.

[W&KO]

Ditto,

There is absolutely no reason and no need to have independent suspension on a caravan .

Live axles are better , stronger, cheaper, don't go out of adjustment and easier to maintain. You can have exactly the same spring rates and shockers as independent without the issues.

I can think of one good reason....

While I don’t think I’d ever tow a van again but if I did I’d have spec it to have air bag suspension.....Same smooth ride as the weight changes and leveling the van.

Hang on that’s two reasons.....

But than again I’d also have electric over hydraulic disc brakes as well.

[roverrescue]

Weeds
You can have air springs and solid axles no problem at all

Independent triller suspension is a solution looking for a problem

It introduces left right load shifting that needs correcting - actually over springing as sway bars are too expensive

Independent suspension was made for bulk trailer makers to simplify production

Bolt/weld on a left or right suspension bogey at what ever track width required ....

It just needed some snazzy marketing to sell it to the public - thanks Kimberley kamper S!!!

Anyways

I agree there is no good reason to have independent suspension on a trailer

S

[PhilipA]

To me the greatest advantage of independent suspension is stability on corrugated dirt roads and particularly on corrugated corners.

My old Camp'o'matic has never stepped out on corrugated corners even when the D2 steps out and sits straight and true on the worst corrugations.
Regards PhilipA.

[barney]

Ditto,

There is absolutely no reason and no need to have independent suspension on a caravan .

Live axles are better , stronger, cheaper, don't go out of adjustment and easier to maintain. You can have exactly the same spring rates and shockers as independent without the issues.

I can only think of one instance where independent suspension might assist a van, and that's where the van has more than one axle. But the fact remains that the whole set-up relies on 3 support points - the tow point, the left wheel and the right wheel. As long as the tow point has good Articulation, there'd be no need for any independent suspension.
Just another way to suck gullible consumers into spending money they don't need to.

[Slunnie]

Just another way to suck gullible consumers into spending money they don't need to.

Yep, I think it is all about marketing as the must have latest and greatest thing, and people obviously want it. Its not a path I would be inclined to go down.

[W&KO]

Weeds
You can have air springs and solid axles no problem at all


S

How available off the shelf?

Still trying to talk the bride into the Offroad boat (or ski) trailer than I’ll pick you brains on air struts on a solid v bagged Independant

[roverrescue]

First Philip
Your trailer behaves well on corrugations not because of independent setup (truly inspite of it)

If you correctly balance load carrying ability and suspension compliance with a solid axle you too will have the same ride characteristics PLUS left right balance.
Not all independent setups ride well- many surge all over the track left to right as the load is pitched left to right with no cross over load path.

Weeds you pretty well highlight the issue at hand!

The “trailer industry” is pretty shallow. Near enough is good enough and because we generally don’t ride in our trailers in Australia no-one really cares !!!

The industry wants as much cross platform compatibility and small engineered packaging size - actual performance is Barely considered.

For an easy example - have a look at the rear spring pack of an XD falcon wagon ... semi elliptical long leaf pack rates to about 1200kg - compare that to a 1200kg spring pack you buy at a trailer shop... may as well just weld the axle to the chassis and air the tyres down - I am serious.

So to answer your question I’m not aware of a in Australia of a commercial trailer based
Multi link solid axle air spring setup

BUT there are lots of options to get there
-Either scalping parts from known good vehicle geometries
-Building multi links from scratch
-buying multi link kits and axles from US supplies like Currie or RuffStuff etc etc etc

Steve

[Pedro_The_Swift]

and yet, apart from home grown setups, this welding/leaf spring setup is exactly the route you want us to go down,,
I'll keep my 30 year old 4 wheel fully independent setup thanks.
and I will take a bucket load of convincing not to go this way on our next van too... not everyone is convinced by shiney benchtops. ( not that new vans HAVE any benchspace... [wink11])
That simplicity stuff is just wrong...

[roverrescue]

Pedro
Tandem axles are a whole different barrel of fish
Does your trailer have any load share between front and rear axle
What is your ATM

The simplicity is a morph of walking beam suspension which worked well in truck trailers for nearly forever

I personally wouldn’t use them as the spring rate will likely be high and compliance low

But I’m always interested in the choices people make

S

[Pedro_The_Swift]

Yep,, seen the walking beams on older trucks,,
and with weight carrying on trucks the main objective I can see why they were used.

4 wheel independent. no load sharing.
ATM around 1800?? Why the??,, In 1990 vans didnt need one, The one I put on the van has departed at some stage, the info is actually on here, somewhere.[bighmmm]