ALKO Rubber Torsion Bar

Weven · Veteran Member

ALKO Rubber Torsion Bar

Eaglemax · Guru

Hi Weven

I owned a t@b caravan, large teardrop, with alko torsion suspension. I'm no expert but I formed the opinion that it was quite "bouncy " in its operation. It doesn't appear to have the same travel than old fashioned leaf springs. But I also believe (again without expertise) that it depends on the van because my t@b weighed only 500kg tare, 750kg atm on 1000kg axles (from memory)...had it been a heavier van the suspension might have operated better.?

I've followed vans going over speed humps. I can tell which ones have torsion suspension due to the above.

However, the torsion suspension is proven and very low maintenance. Not necessarily ideal in every van.
Tony

Weven · Veteran Member

Tony, thanks for your reply, tomorrow I will get the tape out and contact the makers with my specs.

Greg 1 · Guru

My experience with this suspension is on my race car trailer and it works well on that but total weight for car and trailer is only 740kgs.

Mamil · Senior Member

I had the Alko IRS system on my caravan. It's not strictly a torsion bar system as torsion bar usually refers to a metal bar that twists, whereas the Alko system relies on rubber bushes embedded in the axle tube. My understanding is that at correct loading the arm should be roughly parallel to the ground. This type of suspension does tend to bounce quite a bit, and I would advise adding shocks to counteract this if you don't have them already.

I did travel in my caravan once to see what the ride was like, and was surprised at how noisy, rough, and bouncy it was. I 'd certainly secure everything very well before going down rough roads!

I'm not aware the arms can be tuned, but when I talked to Alko they did tell me that the internal rubber bushes do eventually wear and compress and the suspension will sag too much, at which point it needs to be returned to them for replacement bushes which is not an easy or cheap process!

The following table may help determine if your particular setup is correct, it's from the Alko website...

Weven · Veteran Member

Thanks Mamil very helpful.

Mine has off road marked on it so it would be the 1600 to 1800kg range which makes sense given a GTM of 3000kg,s so now gives me something to work with.

I would love to add shocks for an exercise but the fitting to the arm appears problematic.

Mamil · Senior Member

Weven wrote:
Thanks Mamil very helpful.

Mine has off road marked on it so it would be the 1600 to 1800kg range which makes sense given a GTM of 3000kg,s so now gives me something to work with.

I would love to add shocks for an exercise but the fitting to the arm appears problematic.

The arms on mine had brackets welded on to fit the shocks. Don't know if you could weld similar to yours or if you'd need to change the arms - best talk to Alko about that.

Damage 3 (1024x768).jpg

-- Edited by Mamil on Friday 9th of July 2021 03:39:28 PM

Weven · Veteran Member

That bracket position is a surprise, movement at the spot would be minimal. I was thinking at this position.

-- Edited by Weven on Friday 9th of July 2021 09:25:27 PM

landy · Guru

I have the Dexter version of this which is now sold in Australia by Alko alongside there own product. Done about 35000 Ks so far with probably about 1000 Ks of dirt, some of which was a lot rougher than I had planed to take it on but it seems to have handled it all right. Landy

Mike Harding · Guru

My on/off road numbers are about half of Landy's but I have had no issues with my Snowy River SR-19 or contents with its Alko torsion suspension.

Mamil · Senior Member

Weven wrote:
That bracket position is a surprise, movement at the spot would be minimal. I was thinking at this position.

-- Edited by Weven on Friday 9th of July 2021 09:25:27 PM

I think at your position the shock may not be able to handle the full range of travel of the arm, as these things swing quite a lot in use, but anyway that's how mine came stock from Alko so have to assume they've done their sums.

-- Edited by Mamil on Saturday 10th of July 2021 11:38:47 AM

KJB · Guru

Mamil wrote:
Weven wrote:
That bracket position is a surprise, movement at the spot would be minimal. I was thinking at this position.
You would need to make sure the shock absorber is long enough for full suspension travel , wise to have "bump stops " on the suspension arm also. Also be sure there is enough room to mount the top of shock absorber . A big help is to mount the shock absorber on the rear end of the suspension arm (also helps stopping the heat from welding to affect the rubber ) and as far down as practical - you will need a longer shock absorber which is good because but the finess of its operation becomes less critical. I have fitted shock absorbers to this type of suspension and used it ,in the past , but I can say it is not my choice of suspension systems especially for rough or undulating conditions. KB

-- Edited by Weven on Friday 9th of July 2021 09:25:27 PM
I think at your position the shock may not be able to handle the full range of travel of the arm, as these things swing quite a lot in use, but anyway that's how mine came stock from Alko so have to assume they've done their sums.

-- Edited by Mamil on Saturday 10th of July 2021 11:38:47 AM

Weven · Veteran Member

Update on Rubber Suspension.

My measurements have revealed why the ride is undesirable.

Total travel for the Wheel is approximately 55mm.

As the Van sits now, not fully loaded, give or take 150 kg's, the travel left is around 25mm which clearly means the Van is bottoming out regularly on our third world roads. Not good at all.

Also probably why it never wants to sway as there is only a tiny suspension movement.

I am going to keep the Van as it is clearly well built, and nothing has fallen off or broken when obviously it must be absorbing a massive pounding as what amounts to almost no suspension travel to absorb the road shocks.

My preferred update is Simplicity LSC (Load Sharing Coil). The cleverest I have seen. Opinions appreciated.

www.simplicityaxles.com.au/unique-design

My reason being in a previous life I drove a Vehicle which weighed 11500kgs on the front "twin steer" and on 2 beam axles and leaf springs which was upgraded to Load Sharing and the difference in ride quality and handling was a BIG surprise.

Dick0 · Guru

Hi Steve,

My van has the Alko torsion rubber suspension.

I cannot tell you what the fully laden suspension travel is but I do not have any adverse interior effects as you indicate. I assume my van does not bottom out.

The 14" wheels are inflated at 40psi cold and I get very good travel on bitumen and even graded gravel surfaces.

I had worse results with my former van which had leaf sprung suspension.

I would seek advice from a caravan service centre to measure whether the torsion travel is correct.

Weven · Veteran Member

Yes checked with ALKO the travel is correct. I think mine is using up to much to start with. 55mm travel is a worry on our great roads..

landy · Guru

Weven wrote:

Yes checked with ALKO the travel is correct. I think mine is using up to much to start with. 55mm travel is a worry on our great roads..

Looking at the travel I would be inclined to agree as I thought exactly the same as you do. But in my case this has not held true in practice so far. Our last van had Simplicity suspension and we had a lot of problems with it shaking its self apart on corrugations. The new van with a Dexter Axle and limited travel has so far not had any of these problems.
Landy

Weven · Veteran Member

Thanks Landy, going to talk to ALKO again.

Weven · Veteran Member

Landy was your Simplicity load the sharing leaf system? Thanks.

landy · Guru

Weven I am not sure of the different types of Simplicity suspensions but it was an inverted leaf spring supporting 2 swinging arms one on each end. I believe it to be a very strong set up chassis wise and we did do a lot of corrugated roads with it but it took its toll on plenty of screws and caravan fittings.
Landy

Aus-Kiwi · Guru

From way back we had thus type of suspension on trailer . It was a little hard on rubbers in bad or bumpy road conditions . We fitted shocks to limit travel !! It made a heap of difference .

PeterD · Guru

landy wrote:
Weven I am not sure of the different types of Simplicity suspensions but it was an inverted leaf spring supporting 2 swinging arms one on each end.

To find out more have a look here - Simplicity Axles - I think everyone should familiarise themselves with the product. Click through the links and you will find several short videos that explain things.

Dick0 · Guru

Are we talking about rubber torsion suspension or leaf spring suspension?

Weven · Veteran Member

I have ordered 4 x Monroe AIR Shocks and will report results. With the air I will be able to gain some more control regards travel with the added bonus of rebound damping.
According to ALKO my loaded sag is to much as the arms are above horizontal so rather than remove the axle's and have them re rubbered the shocks will give me air bag type suspension

Landy that was Leaf Spring load sharing.

AusK dont you mean shocks to control the damping? If a shock Top's out or Bottom's out in its travel it will destroy it quicker than you can blink an eye. That's why you will see short cables on some to stop the twin shocks bottoming out and bumps stops to avoid topping out.

KJB · Guru

Weven wrote:
I have ordered 4 x Monroe AIR Shocks and will report results. With the air I will be able to gain some more control regards travel with the added bonus of rebound damping.
According to ALKO my loaded sag is to much as the arms are above horizontal so rather than remove the axle's and have them re rubbered the shocks will give me air bag type suspension

Landy that was Leaf Spring load sharing.

AusK dont you mean shocks to control the damping? If a shock Top's out or Bottom's out in its travel it will destroy it quicker than you can blink an eye. That's why you will see short cables on some to stop the twin shocks bottoming out and bumps stops to avoid topping out.

Do not forget that at the point you mount them to the chassis then becomes a "load sharing" point........so the mounting and the chassis at this point need to be "up to the job....." otherwise it will all end in tears ........

Weven · Veteran Member

Yes KJB point taken.........

Weven · Veteran Member

Small Air2.jpg

Taken awhile and yet to road test.... biggrin